feat(sqlite): add SQLite writer for converting PostgreSQL schemas

- Implement SQLite DDL writer to convert PostgreSQL schemas to SQLite-compatible SQL statements.
- Include automatic schema flattening, type mapping, auto-increment detection, and function translation.
- Add templates for creating tables, indexes, unique constraints, check constraints, and foreign keys.
- Implement tests for writer functionality and data type mapping.

README.md

@@ -59,6 +59,7 @@ RelSpec can write database schemas to multiple formats:
 
 #### Database DDL
 - [PostgreSQL](pkg/writers/pgsql/README.md) - PostgreSQL DDL (CREATE TABLE, etc.)
+- [SQLite](pkg/writers/sqlite/README.md) - SQLite DDL with automatic schema flattening
 
 #### Schema Formats
 - [DBML](pkg/writers/dbml/README.md) - Database Markup Language
@@ -185,6 +186,10 @@ relspec convert --from pgsql --from-conn "postgres://..." \
 # Convert DBML to PostgreSQL SQL
 relspec convert --from dbml --from-path schema.dbml \
                 --to pgsql --to-path schema.sql
+
+# Convert PostgreSQL database to SQLite (with automatic schema flattening)
+relspec convert --from pgsql --from-conn "postgres://..." \
+                --to sqlite --to-path sqlite_schema.sql
 ```
 
 ### Schema Validation

TODO.md

@@ -1,43 +1,44 @@
 # RelSpec - TODO List
 
-
 ## Input Readers / Writers
 
 - [✔️] **Database Inspector**
-  - [✔️] PostgreSQL driver
+  - [✔️] PostgreSQL driver (reader + writer)
   - [ ] MySQL driver
-  - [ ] SQLite driver
+  - [✔️] SQLite driver (reader + writer with automatic schema flattening)
   - [ ] MSSQL driver
   - [✔️] Foreign key detection
   - [✔️] Index extraction
-  - [*] .sql file generation with sequence and priority
+  - [✔️] .sql file generation (PostgreSQL, SQLite)
 - [✔️] .dbml: Database Markup Language (DBML) for textual schema representation.
 - [✔️] Prisma schema support (PSL format) .prisma
-- [✔️] Drizzle ORM support .ts (TypeScript / JavaScript)  (Mr. Edd wanted to move from Prisma to Drizzle. If you are bugs, you are welcome to do pull requests or issues)
+- [✔️] Drizzle ORM support .ts (TypeScript / JavaScript) (Mr. Edd wanted to move from Prisma to Drizzle. If you are bugs, you are welcome to do pull requests or issues)
-- [☠️] Entity Framework (.NET) model .edmx  (Fuck no, EDMX files were bloated, verbose XML nightmares—hard to merge, error-prone, and a pain in teams. Microsoft wisely ditched them in EF Core for code-first. Classic overkill from old MS era.)
+- [☠️] Entity Framework (.NET) model .edmx (Fuck no, EDMX files were bloated, verbose XML nightmares—hard to merge, error-prone, and a pain in teams. Microsoft wisely ditched them in EF Core for code-first. Classic overkill from old MS era.)
 - [✔️] TypeORM support
-- [] .hbm.xml / schema.xml: Hibernate/Propel mappings (Java/PHP)  (💲 Someone can do this, not me)
+- [] .hbm.xml / schema.xml: Hibernate/Propel mappings (Java/PHP) (💲 Someone can do this, not me)
 - [ ] Django models.py (Python classes), Sequelize migrations (JS) (💲 Someone can do this, not me)
 - [] .avsc: Avro schema (JSON format for data serialization) (💲 Someone can do this, not me)
 - [✔️] GraphQL schema generation
 
+## UI
 
-## UI 
 - [✔️] Basic UI (I went with tview)
 - [✔️] Save / Load Database
 - [✔️] Schemas / Domains / Tables
-- [  ] Add Relations
+- [ ] Add Relations
-- [  ] Add Indexes
+- [ ] Add Indexes
-- [  ] Add Views
+- [ ] Add Views
-- [  ] Add Sequences
+- [ ] Add Sequences
-- [  ] Add Scripts
+- [ ] Add Scripts
-- [  ] Domain / Table Assignment
+- [ ] Domain / Table Assignment
 
 ## Documentation
+
 - [ ] API documentation (godoc)
 - [ ] Usage examples for each format combination
 
 ## Advanced Features
+
 - [ ] Dry-run mode for validation
 - [x] Diff tool for comparing specifications
 - [ ] Migration script generation
@@ -46,12 +47,13 @@
 - [ ] Watch mode for auto-regeneration
 
 ## Future Considerations
+
 - [ ] Web UI for visual editing
 - [ ] REST API server mode
 - [ ] Support for NoSQL databases
 
-
 ## Performance
+
 - [ ] Concurrent processing for multiple tables
 - [ ] Streaming for large databases
 - [ ] Memory optimization

cmd/relspec/convert.go

@@ -33,6 +33,7 @@ import (
 	wjson "git.warky.dev/wdevs/relspecgo/pkg/writers/json"
 	wpgsql "git.warky.dev/wdevs/relspecgo/pkg/writers/pgsql"
 	wprisma "git.warky.dev/wdevs/relspecgo/pkg/writers/prisma"
+	wsqlite "git.warky.dev/wdevs/relspecgo/pkg/writers/sqlite"
 	wtypeorm "git.warky.dev/wdevs/relspecgo/pkg/writers/typeorm"
 	wyaml "git.warky.dev/wdevs/relspecgo/pkg/writers/yaml"
 )
@@ -84,6 +85,7 @@ Output formats:
   - prisma: Prisma schema files (.prisma)
   - typeorm: TypeORM entity files (TypeScript)
   - pgsql: PostgreSQL SQL schema
+  - sqlite: SQLite SQL schema (with automatic schema flattening)
 
 PostgreSQL Connection String Examples:
   postgres://username:password@localhost:5432/database_name
@@ -346,6 +348,9 @@ func writeDatabase(db *models.Database, dbType, outputPath, packageName, schemaF
 	case "pgsql", "postgres", "postgresql", "sql":
 		writer = wpgsql.NewWriter(writerOpts)
 
+	case "sqlite", "sqlite3":
+		writer = wsqlite.NewWriter(writerOpts)
+
 	case "prisma":
 		writer = wprisma.NewWriter(writerOpts)
 

cmd/relspec/edit.go

@@ -33,6 +33,7 @@ import (
 	wjson "git.warky.dev/wdevs/relspecgo/pkg/writers/json"
 	wpgsql "git.warky.dev/wdevs/relspecgo/pkg/writers/pgsql"
 	wprisma "git.warky.dev/wdevs/relspecgo/pkg/writers/prisma"
+	wsqlite "git.warky.dev/wdevs/relspecgo/pkg/writers/sqlite"
 	wtypeorm "git.warky.dev/wdevs/relspecgo/pkg/writers/typeorm"
 	wyaml "git.warky.dev/wdevs/relspecgo/pkg/writers/yaml"
 )
@@ -87,6 +88,7 @@ Supports reading from and writing to all supported formats:
     - prisma: Prisma schema files (.prisma)
     - typeorm: TypeORM entity files (TypeScript)
     - pgsql: PostgreSQL SQL schema
+    - sqlite: SQLite SQL schema (with automatic schema flattening)
 
 PostgreSQL Connection String Examples:
   postgres://username:password@localhost:5432/database_name
@@ -319,6 +321,8 @@ func writeDatabaseForEdit(dbType, filePath, connString string, db *models.Databa
 		writer = wprisma.NewWriter(&writers.WriterOptions{OutputPath: filePath})
 	case "typeorm":
 		writer = wtypeorm.NewWriter(&writers.WriterOptions{OutputPath: filePath})
+	case "sqlite", "sqlite3":
+		writer = wsqlite.NewWriter(&writers.WriterOptions{OutputPath: filePath})
 	case "pgsql":
 		writer = wpgsql.NewWriter(&writers.WriterOptions{OutputPath: filePath})
 	default:

cmd/relspec/merge.go

@@ -34,6 +34,7 @@ import (
 	wjson "git.warky.dev/wdevs/relspecgo/pkg/writers/json"
 	wpgsql "git.warky.dev/wdevs/relspecgo/pkg/writers/pgsql"
 	wprisma "git.warky.dev/wdevs/relspecgo/pkg/writers/prisma"
+	wsqlite "git.warky.dev/wdevs/relspecgo/pkg/writers/sqlite"
 	wtypeorm "git.warky.dev/wdevs/relspecgo/pkg/writers/typeorm"
 	wyaml "git.warky.dev/wdevs/relspecgo/pkg/writers/yaml"
 )
@@ -385,6 +386,8 @@ func writeDatabaseForMerge(dbType, filePath, connString string, db *models.Datab
 			return fmt.Errorf("%s: file path is required for TypeORM format", label)
 		}
 		writer = wtypeorm.NewWriter(&writers.WriterOptions{OutputPath: filePath, FlattenSchema: flattenSchema})
+	case "sqlite", "sqlite3":
+		writer = wsqlite.NewWriter(&writers.WriterOptions{OutputPath: filePath, FlattenSchema: flattenSchema})
 	case "pgsql":
 		writerOpts := &writers.WriterOptions{OutputPath: filePath, FlattenSchema: flattenSchema}
 		if connString != "" {

pkg/writers/sqlite/README.md

@@ -0,0 +1,215 @@
+# SQLite Writer
+
+SQLite DDL (Data Definition Language) writer for RelSpec. Converts database schemas to SQLite-compatible SQL statements.
+
+## Features
+
+- **Automatic Schema Flattening** - SQLite doesn't support PostgreSQL-style schemas, so table names are automatically flattened (e.g., `public.users` → `public_users`)
+- **Type Mapping** - Converts PostgreSQL data types to SQLite type affinities (TEXT, INTEGER, REAL, NUMERIC, BLOB)
+- **Auto-Increment Detection** - Automatically converts SERIAL types and auto-increment columns to `INTEGER PRIMARY KEY AUTOINCREMENT`
+- **Function Translation** - Converts PostgreSQL functions to SQLite equivalents (e.g., `now()` → `CURRENT_TIMESTAMP`)
+- **Boolean Handling** - Maps boolean values to INTEGER (true=1, false=0)
+- **Constraint Generation** - Creates indexes, unique constraints, and documents foreign keys
+- **Identifier Quoting** - Properly quotes identifiers using double quotes
+
+## Usage
+
+### Convert PostgreSQL to SQLite
+
+```bash
+relspec convert --from pgsql --from-conn "postgres://user:pass@localhost/mydb" \
+                --to sqlite --to-path schema.sql
+```
+
+### Convert DBML to SQLite
+
+```bash
+relspec convert --from dbml --from-path schema.dbml \
+                --to sqlite --to-path schema.sql
+```
+
+### Multi-Schema Databases
+
+SQLite doesn't support schemas, so multi-schema databases are automatically flattened:
+
+```bash
+# Input has auth.users and public.posts
+# Output will have auth_users and public_posts
+relspec convert --from json --from-path multi_schema.json \
+                --to sqlite --to-path flattened.sql
+```
+
+## Type Mapping
+
+| PostgreSQL Type | SQLite Affinity | Examples |
+|----------------|-----------------|----------|
+| TEXT | TEXT | varchar, text, char, citext, uuid, timestamp, json |
+| INTEGER | INTEGER | int, integer, smallint, bigint, serial, boolean |
+| REAL | REAL | real, float, double precision |
+| NUMERIC | NUMERIC | numeric, decimal |
+| BLOB | BLOB | bytea, blob |
+
+## Auto-Increment Handling
+
+Columns are converted to `INTEGER PRIMARY KEY AUTOINCREMENT` when they meet these criteria:
+- Marked as primary key
+- Integer type
+- Have `AutoIncrement` flag set, OR
+- Type contains "serial", OR
+- Default value contains "nextval"
+
+**Example:**
+
+```sql
+-- Input (PostgreSQL)
+CREATE TABLE users (
+    id SERIAL PRIMARY KEY,
+    name VARCHAR(100)
+);
+
+-- Output (SQLite)
+CREATE TABLE "users" (
+    "id" INTEGER PRIMARY KEY AUTOINCREMENT,
+    "name" TEXT
+);
+```
+
+## Default Value Translation
+
+| PostgreSQL | SQLite | Notes |
+|-----------|--------|-------|
+| `now()`, `CURRENT_TIMESTAMP` | `CURRENT_TIMESTAMP` | Timestamp functions |
+| `CURRENT_DATE` | `CURRENT_DATE` | Date function |
+| `CURRENT_TIME` | `CURRENT_TIME` | Time function |
+| `true`, `false` | `1`, `0` | Boolean values |
+| `gen_random_uuid()` | *(removed)* | SQLite has no built-in UUID |
+| `nextval(...)` | *(removed)* | Handled by AUTOINCREMENT |
+
+## Foreign Keys
+
+Foreign keys are generated as commented-out ALTER TABLE statements for reference:
+
+```sql
+-- Foreign key: fk_posts_user_id
+-- ALTER TABLE "posts" ADD CONSTRAINT "posts_fk_posts_user_id"
+--   FOREIGN KEY ("user_id")
+--   REFERENCES "users" ("id");
+-- Note: Foreign keys should be defined in CREATE TABLE for better SQLite compatibility
+```
+
+For production use, define foreign keys directly in the CREATE TABLE statement or execute the ALTER TABLE commands after creating all tables.
+
+## Constraints
+
+- **Primary Keys**: Inline for auto-increment columns, separate constraint for composite keys
+- **Unique Constraints**: Converted to `CREATE UNIQUE INDEX` statements
+- **Check Constraints**: Generated as comments (should be added to CREATE TABLE manually)
+- **Indexes**: Generated without PostgreSQL-specific features (no GIN, GiST, operator classes)
+
+## Output Structure
+
+Generated SQL follows this order:
+
+1. Header comments
+2. `PRAGMA foreign_keys = ON;`
+3. CREATE TABLE statements (sorted by schema, then table)
+4. CREATE INDEX statements
+5. CREATE UNIQUE INDEX statements (for unique constraints)
+6. Check constraint comments
+7. Foreign key comments
+
+## Example
+
+**Input (multi-schema PostgreSQL):**
+
+```sql
+CREATE SCHEMA auth;
+CREATE TABLE auth.users (
+    id SERIAL PRIMARY KEY,
+    username VARCHAR(50) UNIQUE NOT NULL,
+    created_at TIMESTAMP DEFAULT now()
+);
+
+CREATE SCHEMA public;
+CREATE TABLE public.posts (
+    id SERIAL PRIMARY KEY,
+    user_id INTEGER REFERENCES auth.users(id),
+    title VARCHAR(200) NOT NULL,
+    published BOOLEAN DEFAULT false
+);
+```
+
+**Output (SQLite with flattened schemas):**
+
+```sql
+-- SQLite Database Schema
+-- Database: mydb
+-- Generated by RelSpec
+-- Note: Schema names have been flattened (e.g., public.users -> public_users)
+
+-- Enable foreign key constraints
+PRAGMA foreign_keys = ON;
+
+-- Schema: auth (flattened into table names)
+
+CREATE TABLE "auth_users" (
+    "id" INTEGER PRIMARY KEY AUTOINCREMENT,
+    "username" TEXT NOT NULL,
+    "created_at" TEXT DEFAULT CURRENT_TIMESTAMP
+);
+
+CREATE UNIQUE INDEX "auth_users_users_username_key" ON "auth_users" ("username");
+
+-- Schema: public (flattened into table names)
+
+CREATE TABLE "public_posts" (
+    "id" INTEGER PRIMARY KEY AUTOINCREMENT,
+    "user_id" INTEGER NOT NULL,
+    "title" TEXT NOT NULL,
+    "published" INTEGER DEFAULT 0
+);
+
+-- Foreign key: posts_user_id_fkey
+-- ALTER TABLE "public_posts" ADD CONSTRAINT "public_posts_posts_user_id_fkey"
+--   FOREIGN KEY ("user_id")
+--   REFERENCES "auth_users" ("id");
+-- Note: Foreign keys should be defined in CREATE TABLE for better SQLite compatibility
+```
+
+## Programmatic Usage
+
+```go
+import (
+    "git.warky.dev/wdevs/relspecgo/pkg/models"
+    "git.warky.dev/wdevs/relspecgo/pkg/writers"
+    "git.warky.dev/wdevs/relspecgo/pkg/writers/sqlite"
+)
+
+func main() {
+    // Create writer (automatically enables schema flattening)
+    writer := sqlite.NewWriter(&writers.WriterOptions{
+        OutputPath: "schema.sql",
+    })
+
+    // Write database schema
+    db := &models.Database{
+        Name: "mydb",
+        Schemas: []*models.Schema{
+            // ... your schema data
+        },
+    }
+
+    err := writer.WriteDatabase(db)
+    if err != nil {
+        panic(err)
+    }
+}
+```
+
+## Notes
+
+- Schema flattening is **always enabled** for SQLite output (cannot be disabled)
+- Constraint and index names are prefixed with the flattened table name to avoid collisions
+- Generated SQL is compatible with SQLite 3.x
+- Foreign key constraints require `PRAGMA foreign_keys = ON;` to be enforced
+- For complex schemas, review and test the generated SQL before use in production

pkg/writers/sqlite/datatypes.go

@@ -0,0 +1,89 @@
+package sqlite
+
+import (
+	"strings"
+)
+
+// SQLite type affinities
+const (
+	TypeText    = "TEXT"
+	TypeInteger = "INTEGER"
+	TypeReal    = "REAL"
+	TypeNumeric = "NUMERIC"
+	TypeBlob    = "BLOB"
+)
+
+// MapPostgreSQLType maps PostgreSQL data types to SQLite type affinities
+func MapPostgreSQLType(pgType string) string {
+	// Normalize the type
+	normalized := strings.ToLower(strings.TrimSpace(pgType))
+
+	// Remove array notation if present
+	normalized = strings.TrimSuffix(normalized, "[]")
+
+	// Remove precision/scale if present
+	if idx := strings.Index(normalized, "("); idx != -1 {
+		normalized = normalized[:idx]
+	}
+
+	// Map to SQLite type affinity
+	switch normalized {
+	// TEXT affinity
+	case "varchar", "character varying", "text", "char", "character",
+		"citext", "uuid", "timestamp", "timestamptz", "timestamp with time zone",
+		"timestamp without time zone", "date", "time", "timetz", "time with time zone",
+		"time without time zone", "json", "jsonb", "xml", "inet", "cidr", "macaddr":
+		return TypeText
+
+	// INTEGER affinity
+	case "int", "int2", "int4", "int8", "integer", "smallint", "bigint",
+		"serial", "smallserial", "bigserial", "boolean", "bool":
+		return TypeInteger
+
+	// REAL affinity
+	case "real", "float", "float4", "float8", "double precision":
+		return TypeReal
+
+	// NUMERIC affinity
+	case "numeric", "decimal", "money":
+		return TypeNumeric
+
+	// BLOB affinity
+	case "bytea", "blob":
+		return TypeBlob
+
+	default:
+		// Default to TEXT for unknown types
+		return TypeText
+	}
+}
+
+// IsIntegerType checks if a column type should be treated as integer
+func IsIntegerType(colType string) bool {
+	normalized := strings.ToLower(strings.TrimSpace(colType))
+	normalized = strings.TrimSuffix(normalized, "[]")
+	if idx := strings.Index(normalized, "("); idx != -1 {
+		normalized = normalized[:idx]
+	}
+
+	switch normalized {
+	case "int", "int2", "int4", "int8", "integer", "smallint", "bigint",
+		"serial", "smallserial", "bigserial":
+		return true
+	default:
+		return false
+	}
+}
+
+// MapBooleanValue converts PostgreSQL boolean literals to SQLite (0/1)
+func MapBooleanValue(value string) string {
+	normalized := strings.ToLower(strings.TrimSpace(value))
+	switch normalized {
+	case "true", "t", "yes", "y", "1":
+		return "1"
+	case "false", "f", "no", "n", "0":
+		return "0"
+	default:
+		return value
+	}
+}

pkg/writers/sqlite/template_functions.go

@@ -0,0 +1,146 @@
+package sqlite
+
+import (
+	"fmt"
+	"strings"
+	"text/template"
+
+	"git.warky.dev/wdevs/relspecgo/pkg/models"
+	"git.warky.dev/wdevs/relspecgo/pkg/writers"
+)
+
+// GetTemplateFuncs returns template functions for SQLite SQL generation
+func GetTemplateFuncs(opts *writers.WriterOptions) template.FuncMap {
+	return template.FuncMap{
+		"quote_ident":      QuoteIdentifier,
+		"map_type":         MapPostgreSQLType,
+		"is_autoincrement": IsAutoIncrementCandidate,
+		"qualified_table_name": func(schema, table string) string {
+			return writers.QualifiedTableName(schema, table, opts.FlattenSchema)
+		},
+		"format_default": FormatDefault,
+		"format_constraint_name": func(schema, table, constraint string) string {
+			return FormatConstraintName(schema, table, constraint, opts)
+		},
+		"join":  strings.Join,
+		"lower": strings.ToLower,
+		"upper": strings.ToUpper,
+	}
+}
+
+// QuoteIdentifier quotes an identifier for SQLite (double quotes)
+func QuoteIdentifier(name string) string {
+	// SQLite uses double quotes for identifiers
+	// Escape any existing double quotes by doubling them
+	escaped := strings.ReplaceAll(name, `"`, `""`)
+	return fmt.Sprintf(`"%s"`, escaped)
+}
+
+// IsAutoIncrementCandidate checks if a column should use AUTOINCREMENT
+func IsAutoIncrementCandidate(col *models.Column) bool {
+	// Must be a primary key
+	if !col.IsPrimaryKey {
+		return false
+	}
+
+	// Must be an integer type
+	if !IsIntegerType(col.Type) {
+		return false
+	}
+
+	// Check AutoIncrement field
+	if col.AutoIncrement {
+		return true
+	}
+
+	// Check if default suggests auto-increment
+	if col.Default != nil {
+		defaultStr, ok := col.Default.(string)
+		if ok {
+			defaultLower := strings.ToLower(defaultStr)
+			if strings.Contains(defaultLower, "nextval") ||
+				strings.Contains(defaultLower, "autoincrement") ||
+				strings.Contains(defaultLower, "auto_increment") {
+				return true
+			}
+		}
+	}
+
+	// Serial types are auto-increment
+	typeLower := strings.ToLower(col.Type)
+	return strings.Contains(typeLower, "serial")
+}
+
+// FormatDefault formats a default value for SQLite
+func FormatDefault(col *models.Column) string {
+	if col.Default == nil {
+		return ""
+	}
+
+	// Skip auto-increment defaults (handled by AUTOINCREMENT keyword)
+	if IsAutoIncrementCandidate(col) {
+		return ""
+	}
+
+	// Convert to string
+	defaultStr, ok := col.Default.(string)
+	if !ok {
+		// If not a string, convert to string representation
+		defaultStr = fmt.Sprintf("%v", col.Default)
+	}
+
+	if defaultStr == "" {
+		return ""
+	}
+
+	// Convert PostgreSQL-specific functions to SQLite equivalents
+	defaultLower := strings.ToLower(defaultStr)
+
+	// Current timestamp functions
+	if strings.Contains(defaultLower, "current_timestamp") ||
+		strings.Contains(defaultLower, "now()") {
+		return "CURRENT_TIMESTAMP"
+	}
+
+	// Current date
+	if strings.Contains(defaultLower, "current_date") {
+		return "CURRENT_DATE"
+	}
+
+	// Current time
+	if strings.Contains(defaultLower, "current_time") {
+		return "CURRENT_TIME"
+	}
+
+	// Boolean values
+	sqliteType := MapPostgreSQLType(col.Type)
+	if sqliteType == TypeInteger {
+		typeLower := strings.ToLower(col.Type)
+		if strings.Contains(typeLower, "bool") {
+			return MapBooleanValue(defaultStr)
+		}
+	}
+
+	// UUID generation - SQLite doesn't have built-in UUID, comment it out
+	if strings.Contains(defaultLower, "uuid") || strings.Contains(defaultLower, "gen_random_uuid") {
+		return "" // Remove UUID defaults, users must handle this
+	}
+
+	// Remove PostgreSQL-specific casting
+	defaultStr = strings.ReplaceAll(defaultStr, "::text", "")
+	defaultStr = strings.ReplaceAll(defaultStr, "::integer", "")
+	defaultStr = strings.ReplaceAll(defaultStr, "::bigint", "")
+	defaultStr = strings.ReplaceAll(defaultStr, "::boolean", "")
+
+	return defaultStr
+}
+
+// FormatConstraintName formats a constraint name with table prefix if flattening
+func FormatConstraintName(schema, table, constraint string, opts *writers.WriterOptions) string {
+	if opts.FlattenSchema && schema != "" {
+		// Prefix constraint with flattened table name
+		flatTable := writers.QualifiedTableName(schema, table, opts.FlattenSchema)
+		return fmt.Sprintf("%s_%s", flatTable, constraint)
+	}
+	return constraint
+}

pkg/writers/sqlite/templates.go

@@ -0,0 +1,174 @@
+package sqlite
+
+import (
+	"bytes"
+	"embed"
+	"fmt"
+	"text/template"
+
+	"git.warky.dev/wdevs/relspecgo/pkg/models"
+	"git.warky.dev/wdevs/relspecgo/pkg/writers"
+)
+
+//go:embed templates/*.tmpl
+var templateFS embed.FS
+
+// TemplateExecutor manages and executes SQLite SQL templates
+type TemplateExecutor struct {
+	templates *template.Template
+	options   *writers.WriterOptions
+}
+
+// NewTemplateExecutor creates a new template executor for SQLite
+func NewTemplateExecutor(opts *writers.WriterOptions) (*TemplateExecutor, error) {
+	// Create template with SQLite-specific functions
+	funcMap := GetTemplateFuncs(opts)
+
+	tmpl, err := template.New("").Funcs(funcMap).ParseFS(templateFS, "templates/*.tmpl")
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse templates: %w", err)
+	}
+
+	return &TemplateExecutor{
+		templates: tmpl,
+		options:   opts,
+	}, nil
+}
+
+// Template data structures
+
+// TableTemplateData contains data for table template
+type TableTemplateData struct {
+	Schema     string
+	Name       string
+	Columns    []*models.Column
+	PrimaryKey *models.Constraint
+}
+
+// IndexTemplateData contains data for index template
+type IndexTemplateData struct {
+	Schema  string
+	Table   string
+	Name    string
+	Columns []string
+}
+
+// ConstraintTemplateData contains data for constraint templates
+type ConstraintTemplateData struct {
+	Schema         string
+	Table          string
+	Name           string
+	Columns        []string
+	Expression     string
+	ForeignSchema  string
+	ForeignTable   string
+	ForeignColumns []string
+	OnDelete       string
+	OnUpdate       string
+}
+
+// Execute methods
+
+// ExecutePragmaForeignKeys executes the pragma foreign keys template
+func (te *TemplateExecutor) ExecutePragmaForeignKeys() (string, error) {
+	var buf bytes.Buffer
+	err := te.templates.ExecuteTemplate(&buf, "pragma_foreign_keys.tmpl", nil)
+	if err != nil {
+		return "", fmt.Errorf("failed to execute pragma_foreign_keys template: %w", err)
+	}
+	return buf.String(), nil
+}
+
+// ExecuteCreateTable executes the create table template
+func (te *TemplateExecutor) ExecuteCreateTable(data TableTemplateData) (string, error) {
+	var buf bytes.Buffer
+	err := te.templates.ExecuteTemplate(&buf, "create_table.tmpl", data)
+	if err != nil {
+		return "", fmt.Errorf("failed to execute create_table template: %w", err)
+	}
+	return buf.String(), nil
+}
+
+// ExecuteCreateIndex executes the create index template
+func (te *TemplateExecutor) ExecuteCreateIndex(data IndexTemplateData) (string, error) {
+	var buf bytes.Buffer
+	err := te.templates.ExecuteTemplate(&buf, "create_index.tmpl", data)
+	if err != nil {
+		return "", fmt.Errorf("failed to execute create_index template: %w", err)
+	}
+	return buf.String(), nil
+}
+
+// ExecuteCreateUniqueConstraint executes the create unique constraint template
+func (te *TemplateExecutor) ExecuteCreateUniqueConstraint(data ConstraintTemplateData) (string, error) {
+	var buf bytes.Buffer
+	err := te.templates.ExecuteTemplate(&buf, "create_unique_constraint.tmpl", data)
+	if err != nil {
+		return "", fmt.Errorf("failed to execute create_unique_constraint template: %w", err)
+	}
+	return buf.String(), nil
+}
+
+// ExecuteCreateCheckConstraint executes the create check constraint template
+func (te *TemplateExecutor) ExecuteCreateCheckConstraint(data ConstraintTemplateData) (string, error) {
+	var buf bytes.Buffer
+	err := te.templates.ExecuteTemplate(&buf, "create_check_constraint.tmpl", data)
+	if err != nil {
+		return "", fmt.Errorf("failed to execute create_check_constraint template: %w", err)
+	}
+	return buf.String(), nil
+}
+
+// ExecuteCreateForeignKey executes the create foreign key template
+func (te *TemplateExecutor) ExecuteCreateForeignKey(data ConstraintTemplateData) (string, error) {
+	var buf bytes.Buffer
+	err := te.templates.ExecuteTemplate(&buf, "create_foreign_key.tmpl", data)
+	if err != nil {
+		return "", fmt.Errorf("failed to execute create_foreign_key template: %w", err)
+	}
+	return buf.String(), nil
+}
+
+// Helper functions to build template data from models
+
+// BuildTableTemplateData builds TableTemplateData from a models.Table
+func BuildTableTemplateData(schema string, table *models.Table) TableTemplateData {
+	// Get sorted columns
+	columns := make([]*models.Column, 0, len(table.Columns))
+	for _, col := range table.Columns {
+		columns = append(columns, col)
+	}
+
+	// Find primary key constraint
+	var pk *models.Constraint
+	for _, constraint := range table.Constraints {
+		if constraint.Type == models.PrimaryKeyConstraint {
+			pk = constraint
+			break
+		}
+	}
+
+	// If no explicit primary key constraint, build one from columns with IsPrimaryKey=true
+	if pk == nil {
+		pkCols := []string{}
+		for _, col := range table.Columns {
+			if col.IsPrimaryKey {
+				pkCols = append(pkCols, col.Name)
+			}
+		}
+		if len(pkCols) > 0 {
+			pk = &models.Constraint{
+				Name:    "pk_" + table.Name,
+				Type:    models.PrimaryKeyConstraint,
+				Columns: pkCols,
+			}
+		}
+	}
+
+	return TableTemplateData{
+		Schema:     schema,
+		Name:       table.Name,
+		Columns:    columns,
+		PrimaryKey: pk,
+	}
+}

pkg/writers/sqlite/templates/create_check_constraint.tmpl

@@ -0,0 +1,4 @@
+-- Check constraint: {{.Name}}
+-- {{.Expression}}
+-- Note: SQLite supports CHECK constraints in CREATE TABLE or ALTER TABLE ADD CHECK
+-- This must be added manually to the table definition above

pkg/writers/sqlite/templates/create_foreign_key.tmpl

@@ -0,0 +1,6 @@
+-- Foreign key: {{.Name}}
+-- ALTER TABLE {{quote_ident (qualified_table_name .Schema .Table)}} ADD CONSTRAINT {{quote_ident (format_constraint_name .Schema .Table .Name)}}
+--   FOREIGN KEY ({{range $i, $col := .Columns}}{{if $i}}, {{end}}{{quote_ident $col}}{{end}})
+--   REFERENCES {{quote_ident (qualified_table_name .ForeignSchema .ForeignTable)}} ({{range $i, $col := .ForeignColumns}}{{if $i}}, {{end}}{{quote_ident $col}}{{end}})
+--   {{if .OnDelete}}ON DELETE {{.OnDelete}}{{end}}{{if .OnUpdate}} ON UPDATE {{.OnUpdate}}{{end}};
+-- Note: Foreign keys should be defined in CREATE TABLE for better SQLite compatibility

pkg/writers/sqlite/templates/create_index.tmpl

@@ -0,0 +1 @@
+CREATE INDEX {{quote_ident (format_constraint_name .Schema .Table .Name)}} ON {{quote_ident (qualified_table_name .Schema .Table)}} ({{range $i, $col := .Columns}}{{if $i}}, {{end}}{{quote_ident $col}}{{end}});

pkg/writers/sqlite/templates/create_table.tmpl

@@ -0,0 +1,9 @@
+CREATE TABLE {{quote_ident (qualified_table_name .Schema .Name)}} (
+{{- $hasAutoIncrement := false}}
+{{- range $i, $col := .Columns}}{{if $i}},{{end}}
+    {{quote_ident $col.Name}} {{map_type $col.Type}}{{if is_autoincrement $col}}{{$hasAutoIncrement = true}} PRIMARY KEY AUTOINCREMENT{{else}}{{if $col.NotNull}} NOT NULL{{end}}{{if ne (format_default $col) ""}} DEFAULT {{format_default $col}}{{end}}{{end}}
+{{- end}}
+{{- if and .PrimaryKey (not $hasAutoIncrement)}}{{if gt (len .Columns) 0}},{{end}}
+    PRIMARY KEY ({{range $i, $colName := .PrimaryKey.Columns}}{{if $i}}, {{end}}{{quote_ident $colName}}{{end}})
+{{- end}}
+);

pkg/writers/sqlite/templates/create_unique_constraint.tmpl

@@ -0,0 +1 @@
+CREATE UNIQUE INDEX {{quote_ident (format_constraint_name .Schema .Table .Name)}} ON {{quote_ident (qualified_table_name .Schema .Table)}} ({{range $i, $col := .Columns}}{{if $i}}, {{end}}{{quote_ident $col}}{{end}});

pkg/writers/sqlite/templates/pragma_foreign_keys.tmpl

@@ -0,0 +1,2 @@
+-- Enable foreign key constraints
+PRAGMA foreign_keys = ON;

pkg/writers/sqlite/writer.go

@@ -0,0 +1,291 @@
+package sqlite
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"git.warky.dev/wdevs/relspecgo/pkg/models"
+	"git.warky.dev/wdevs/relspecgo/pkg/writers"
+)
+
+// Writer implements the Writer interface for SQLite SQL output
+type Writer struct {
+	options  *writers.WriterOptions
+	writer   io.Writer
+	executor *TemplateExecutor
+}
+
+// NewWriter creates a new SQLite SQL writer
+// SQLite doesn't support schemas, so FlattenSchema is automatically enabled
+func NewWriter(options *writers.WriterOptions) *Writer {
+	// Force schema flattening for SQLite
+	options.FlattenSchema = true
+
+	executor, _ := NewTemplateExecutor(options)
+	return &Writer{
+		options:  options,
+		executor: executor,
+	}
+}
+
+// WriteDatabase writes the entire database schema as SQLite SQL
+func (w *Writer) WriteDatabase(db *models.Database) error {
+	var writer io.Writer
+	var file *os.File
+	var err error
+
+	// Use existing writer if already set (for testing)
+	if w.writer != nil {
+		writer = w.writer
+	} else if w.options.OutputPath != "" {
+		// Determine output destination
+		file, err = os.Create(w.options.OutputPath)
+		if err != nil {
+			return fmt.Errorf("failed to create output file: %w", err)
+		}
+		defer file.Close()
+		writer = file
+	} else {
+		writer = os.Stdout
+	}
+
+	w.writer = writer
+
+	// Write header comment
+	fmt.Fprintf(w.writer, "-- SQLite Database Schema\n")
+	fmt.Fprintf(w.writer, "-- Database: %s\n", db.Name)
+	fmt.Fprintf(w.writer, "-- Generated by RelSpec\n")
+	fmt.Fprintf(w.writer, "-- Note: Schema names have been flattened (e.g., public.users -> public_users)\n\n")
+
+	// Enable foreign keys
+	pragma, err := w.executor.ExecutePragmaForeignKeys()
+	if err != nil {
+		return fmt.Errorf("failed to generate pragma statement: %w", err)
+	}
+	fmt.Fprintf(w.writer, "%s\n", pragma)
+
+	// Process each schema in the database
+	for _, schema := range db.Schemas {
+		if err := w.WriteSchema(schema); err != nil {
+			return fmt.Errorf("failed to write schema %s: %w", schema.Name, err)
+		}
+	}
+
+	return nil
+}
+
+// WriteSchema writes a single schema as SQLite SQL
+func (w *Writer) WriteSchema(schema *models.Schema) error {
+	// SQLite doesn't have schemas, so we just write a comment
+	if schema.Name != "" {
+		fmt.Fprintf(w.writer, "-- Schema: %s (flattened into table names)\n\n", schema.Name)
+	}
+
+	// Phase 1: Create tables
+	for _, table := range schema.Tables {
+		if err := w.writeTable(schema.Name, table); err != nil {
+			return fmt.Errorf("failed to write table %s: %w", table.Name, err)
+		}
+	}
+
+	// Phase 2: Create indexes
+	for _, table := range schema.Tables {
+		if err := w.writeIndexes(schema.Name, table); err != nil {
+			return fmt.Errorf("failed to write indexes for table %s: %w", table.Name, err)
+		}
+	}
+
+	// Phase 3: Create unique constraints (as unique indexes)
+	for _, table := range schema.Tables {
+		if err := w.writeUniqueConstraints(schema.Name, table); err != nil {
+			return fmt.Errorf("failed to write unique constraints for table %s: %w", table.Name, err)
+		}
+	}
+
+	// Phase 4: Check constraints (as comments, since SQLite requires them in CREATE TABLE)
+	for _, table := range schema.Tables {
+		if err := w.writeCheckConstraints(schema.Name, table); err != nil {
+			return fmt.Errorf("failed to write check constraints for table %s: %w", table.Name, err)
+		}
+	}
+
+	// Phase 5: Foreign keys (as comments for compatibility)
+	for _, table := range schema.Tables {
+		if err := w.writeForeignKeys(schema.Name, table); err != nil {
+			return fmt.Errorf("failed to write foreign keys for table %s: %w", table.Name, err)
+		}
+	}
+
+	return nil
+}
+
+// WriteTable writes a single table as SQLite SQL
+func (w *Writer) WriteTable(table *models.Table) error {
+	return w.writeTable("", table)
+}
+
+// writeTable is the internal implementation
+func (w *Writer) writeTable(schema string, table *models.Table) error {
+	// Build table template data
+	data := BuildTableTemplateData(schema, table)
+
+	// Execute template
+	sql, err := w.executor.ExecuteCreateTable(data)
+	if err != nil {
+		return fmt.Errorf("failed to execute create table template: %w", err)
+	}
+
+	fmt.Fprintf(w.writer, "%s\n", sql)
+	return nil
+}
+
+// writeIndexes writes indexes for a table
+func (w *Writer) writeIndexes(schema string, table *models.Table) error {
+	for _, index := range table.Indexes {
+		// Skip primary key indexes
+		if strings.HasSuffix(index.Name, "_pkey") {
+			continue
+		}
+
+		// Skip unique indexes (handled separately as unique constraints)
+		if index.Unique {
+			continue
+		}
+
+		data := IndexTemplateData{
+			Schema:  schema,
+			Table:   table.Name,
+			Name:    index.Name,
+			Columns: index.Columns,
+		}
+
+		sql, err := w.executor.ExecuteCreateIndex(data)
+		if err != nil {
+			return fmt.Errorf("failed to execute create index template: %w", err)
+		}
+
+		fmt.Fprintf(w.writer, "%s\n", sql)
+	}
+
+	return nil
+}
+
+// writeUniqueConstraints writes unique constraints as unique indexes
+func (w *Writer) writeUniqueConstraints(schema string, table *models.Table) error {
+	for _, constraint := range table.Constraints {
+		if constraint.Type != models.UniqueConstraint {
+			continue
+		}
+
+		data := ConstraintTemplateData{
+			Schema:  schema,
+			Table:   table.Name,
+			Name:    constraint.Name,
+			Columns: constraint.Columns,
+		}
+
+		sql, err := w.executor.ExecuteCreateUniqueConstraint(data)
+		if err != nil {
+			return fmt.Errorf("failed to execute create unique constraint template: %w", err)
+		}
+
+		fmt.Fprintf(w.writer, "%s\n", sql)
+	}
+
+	// Also handle unique indexes from the Indexes map
+	for _, index := range table.Indexes {
+		if !index.Unique {
+			continue
+		}
+
+		// Skip if already handled as a constraint
+		alreadyHandled := false
+		for _, constraint := range table.Constraints {
+			if constraint.Type == models.UniqueConstraint && constraint.Name == index.Name {
+				alreadyHandled = true
+				break
+			}
+		}
+		if alreadyHandled {
+			continue
+		}
+
+		data := ConstraintTemplateData{
+			Schema:  schema,
+			Table:   table.Name,
+			Name:    index.Name,
+			Columns: index.Columns,
+		}
+
+		sql, err := w.executor.ExecuteCreateUniqueConstraint(data)
+		if err != nil {
+			return fmt.Errorf("failed to execute create unique index template: %w", err)
+		}
+
+		fmt.Fprintf(w.writer, "%s\n", sql)
+	}
+
+	return nil
+}
+
+// writeCheckConstraints writes check constraints as comments
+func (w *Writer) writeCheckConstraints(schema string, table *models.Table) error {
+	for _, constraint := range table.Constraints {
+		if constraint.Type != models.CheckConstraint {
+			continue
+		}
+
+		data := ConstraintTemplateData{
+			Schema:     schema,
+			Table:      table.Name,
+			Name:       constraint.Name,
+			Expression: constraint.Expression,
+		}
+
+		sql, err := w.executor.ExecuteCreateCheckConstraint(data)
+		if err != nil {
+			return fmt.Errorf("failed to execute create check constraint template: %w", err)
+		}
+
+		fmt.Fprintf(w.writer, "%s\n", sql)
+	}
+
+	return nil
+}
+
+// writeForeignKeys writes foreign keys as comments
+func (w *Writer) writeForeignKeys(schema string, table *models.Table) error {
+	for _, constraint := range table.Constraints {
+		if constraint.Type != models.ForeignKeyConstraint {
+			continue
+		}
+
+		refSchema := constraint.ReferencedSchema
+		if refSchema == "" {
+			refSchema = schema
+		}
+
+		data := ConstraintTemplateData{
+			Schema:         schema,
+			Table:          table.Name,
+			Name:           constraint.Name,
+			Columns:        constraint.Columns,
+			ForeignSchema:  refSchema,
+			ForeignTable:   constraint.ReferencedTable,
+			ForeignColumns: constraint.ReferencedColumns,
+			OnDelete:       constraint.OnDelete,
+			OnUpdate:       constraint.OnUpdate,
+		}
+
+		sql, err := w.executor.ExecuteCreateForeignKey(data)
+		if err != nil {
+			return fmt.Errorf("failed to execute create foreign key template: %w", err)
+		}
+
+		fmt.Fprintf(w.writer, "%s\n", sql)
+	}
+
+	return nil
+}

pkg/writers/sqlite/writer_test.go

@@ -0,0 +1,418 @@
+package sqlite
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+
+	"git.warky.dev/wdevs/relspecgo/pkg/models"
+	"git.warky.dev/wdevs/relspecgo/pkg/writers"
+)
+
+func TestNewWriter(t *testing.T) {
+	opts := &writers.WriterOptions{
+		OutputPath:     "/tmp/test.sql",
+		FlattenSchema:  false, // Should be forced to true
+	}
+
+	writer := NewWriter(opts)
+
+	if !writer.options.FlattenSchema {
+		t.Error("Expected FlattenSchema to be forced to true for SQLite")
+	}
+}
+
+func TestWriteDatabase(t *testing.T) {
+	db := &models.Database{
+		Name: "testdb",
+		Schemas: []*models.Schema{
+			{
+				Name: "public",
+				Tables: []*models.Table{
+					{
+						Name: "users",
+						Columns: map[string]*models.Column{
+							"id": {
+								Name:         "id",
+								Type:         "serial",
+								NotNull:      true,
+								IsPrimaryKey: true,
+								Default:      "nextval('users_id_seq'::regclass)",
+							},
+							"email": {
+								Name:    "email",
+								Type:    "varchar(255)",
+								NotNull: true,
+							},
+							"active": {
+								Name:    "active",
+								Type:    "boolean",
+								NotNull: true,
+								Default: "true",
+							},
+						},
+						Constraints: map[string]*models.Constraint{
+							"pk_users": {
+								Name:    "pk_users",
+								Type:    models.PrimaryKeyConstraint,
+								Columns: []string{"id"},
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+
+	var buf bytes.Buffer
+	opts := &writers.WriterOptions{}
+	writer := NewWriter(opts)
+	writer.writer = &buf
+
+	err := writer.WriteDatabase(db)
+	if err != nil {
+		t.Fatalf("WriteDatabase failed: %v", err)
+	}
+
+	output := buf.String()
+
+	// Check for expected elements
+	if !strings.Contains(output, "PRAGMA foreign_keys = ON") {
+		t.Error("Expected PRAGMA foreign_keys statement")
+	}
+
+	if !strings.Contains(output, "CREATE TABLE") {
+		t.Error("Expected CREATE TABLE statement")
+	}
+
+	if !strings.Contains(output, "\"public_users\"") {
+		t.Error("Expected flattened table name public_users")
+	}
+
+	if !strings.Contains(output, "INTEGER PRIMARY KEY AUTOINCREMENT") {
+		t.Error("Expected autoincrement for serial primary key")
+	}
+
+	if !strings.Contains(output, "TEXT") {
+		t.Error("Expected TEXT type for varchar")
+	}
+
+	// Boolean should be mapped to INTEGER with default 1
+	if !strings.Contains(output, "active") {
+		t.Error("Expected active column")
+	}
+}
+
+func TestDataTypeMapping(t *testing.T) {
+	tests := []struct {
+		pgType   string
+		expected string
+	}{
+		{"varchar(255)", "TEXT"},
+		{"text", "TEXT"},
+		{"integer", "INTEGER"},
+		{"bigint", "INTEGER"},
+		{"serial", "INTEGER"},
+		{"boolean", "INTEGER"},
+		{"real", "REAL"},
+		{"double precision", "REAL"},
+		{"numeric(10,2)", "NUMERIC"},
+		{"decimal", "NUMERIC"},
+		{"bytea", "BLOB"},
+		{"timestamp", "TEXT"},
+		{"uuid", "TEXT"},
+		{"json", "TEXT"},
+		{"jsonb", "TEXT"},
+	}
+
+	for _, tt := range tests {
+		result := MapPostgreSQLType(tt.pgType)
+		if result != tt.expected {
+			t.Errorf("MapPostgreSQLType(%q) = %q, want %q", tt.pgType, result, tt.expected)
+		}
+	}
+}
+
+func TestIsAutoIncrementCandidate(t *testing.T) {
+	tests := []struct {
+		name     string
+		col      *models.Column
+		expected bool
+	}{
+		{
+			name: "serial primary key",
+			col: &models.Column{
+				Name:         "id",
+				Type:         "serial",
+				IsPrimaryKey: true,
+				Default:      "nextval('seq')",
+			},
+			expected: true,
+		},
+		{
+			name: "integer primary key with nextval",
+			col: &models.Column{
+				Name:         "id",
+				Type:         "integer",
+				IsPrimaryKey: true,
+				Default:      "nextval('users_id_seq'::regclass)",
+			},
+			expected: true,
+		},
+		{
+			name: "integer not primary key",
+			col: &models.Column{
+				Name:         "count",
+				Type:         "integer",
+				IsPrimaryKey: false,
+				Default:      "0",
+			},
+			expected: false,
+		},
+		{
+			name: "varchar primary key",
+			col: &models.Column{
+				Name:         "code",
+				Type:         "varchar",
+				IsPrimaryKey: true,
+			},
+			expected: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := IsAutoIncrementCandidate(tt.col)
+			if result != tt.expected {
+				t.Errorf("IsAutoIncrementCandidate() = %v, want %v", result, tt.expected)
+			}
+		})
+	}
+}
+
+func TestFormatDefault(t *testing.T) {
+	tests := []struct {
+		name     string
+		col      *models.Column
+		expected string
+	}{
+		{
+			name: "current_timestamp",
+			col: &models.Column{
+				Type:    "timestamp",
+				Default: "CURRENT_TIMESTAMP",
+			},
+			expected: "CURRENT_TIMESTAMP",
+		},
+		{
+			name: "now()",
+			col: &models.Column{
+				Type:    "timestamp",
+				Default: "now()",
+			},
+			expected: "CURRENT_TIMESTAMP",
+		},
+		{
+			name: "boolean true",
+			col: &models.Column{
+				Type:    "boolean",
+				Default: "true",
+			},
+			expected: "1",
+		},
+		{
+			name: "boolean false",
+			col: &models.Column{
+				Type:    "boolean",
+				Default: "false",
+			},
+			expected: "0",
+		},
+		{
+			name: "serial autoincrement",
+			col: &models.Column{
+				Type:         "serial",
+				IsPrimaryKey: true,
+				Default:      "nextval('seq')",
+			},
+			expected: "",
+		},
+		{
+			name: "uuid default removed",
+			col: &models.Column{
+				Type:    "uuid",
+				Default: "gen_random_uuid()",
+			},
+			expected: "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := FormatDefault(tt.col)
+			if result != tt.expected {
+				t.Errorf("FormatDefault() = %q, want %q", result, tt.expected)
+			}
+		})
+	}
+}
+
+func TestWriteSchema_MultiSchema(t *testing.T) {
+	db := &models.Database{
+		Name: "testdb",
+		Schemas: []*models.Schema{
+			{
+				Name: "auth",
+				Tables: []*models.Table{
+					{
+						Name: "sessions",
+						Columns: map[string]*models.Column{
+							"id": {
+								Name:         "id",
+								Type:         "uuid",
+								NotNull:      true,
+								IsPrimaryKey: true,
+							},
+						},
+						Constraints: map[string]*models.Constraint{
+							"pk_sessions": {
+								Name:    "pk_sessions",
+								Type:    models.PrimaryKeyConstraint,
+								Columns: []string{"id"},
+							},
+						},
+					},
+				},
+			},
+			{
+				Name: "public",
+				Tables: []*models.Table{
+					{
+						Name: "posts",
+						Columns: map[string]*models.Column{
+							"id": {
+								Name:         "id",
+								Type:         "integer",
+								NotNull:      true,
+								IsPrimaryKey: true,
+							},
+						},
+						Constraints: map[string]*models.Constraint{
+							"pk_posts": {
+								Name:    "pk_posts",
+								Type:    models.PrimaryKeyConstraint,
+								Columns: []string{"id"},
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+
+	var buf bytes.Buffer
+	opts := &writers.WriterOptions{}
+	writer := NewWriter(opts)
+	writer.writer = &buf
+
+	err := writer.WriteDatabase(db)
+	if err != nil {
+		t.Fatalf("WriteDatabase failed: %v", err)
+	}
+
+	output := buf.String()
+
+	// Check for flattened table names from both schemas
+	if !strings.Contains(output, "\"auth_sessions\"") {
+		t.Error("Expected flattened table name auth_sessions")
+	}
+
+	if !strings.Contains(output, "\"public_posts\"") {
+		t.Error("Expected flattened table name public_posts")
+	}
+}
+
+func TestWriteIndexes(t *testing.T) {
+	table := &models.Table{
+		Name: "users",
+		Columns: map[string]*models.Column{
+			"email": {
+				Name: "email",
+				Type: "varchar(255)",
+			},
+		},
+		Indexes: map[string]*models.Index{
+			"idx_users_email": {
+				Name:    "idx_users_email",
+				Columns: []string{"email"},
+			},
+		},
+	}
+
+	var buf bytes.Buffer
+	opts := &writers.WriterOptions{}
+	writer := NewWriter(opts)
+	writer.writer = &buf
+
+	err := writer.writeIndexes("public", table)
+	if err != nil {
+		t.Fatalf("writeIndexes failed: %v", err)
+	}
+
+	output := buf.String()
+
+	if !strings.Contains(output, "CREATE INDEX") {
+		t.Error("Expected CREATE INDEX statement")
+	}
+
+	if !strings.Contains(output, "public_users_idx_users_email") {
+		t.Errorf("Expected flattened index name public_users_idx_users_email, got output:\n%s", output)
+	}
+}
+
+func TestWriteUniqueConstraints(t *testing.T) {
+	table := &models.Table{
+		Name: "users",
+		Constraints: map[string]*models.Constraint{
+			"uk_users_email": {
+				Name:    "uk_users_email",
+				Type:    models.UniqueConstraint,
+				Columns: []string{"email"},
+			},
+		},
+	}
+
+	var buf bytes.Buffer
+	opts := &writers.WriterOptions{}
+	writer := NewWriter(opts)
+	writer.writer = &buf
+
+	err := writer.writeUniqueConstraints("public", table)
+	if err != nil {
+		t.Fatalf("writeUniqueConstraints failed: %v", err)
+	}
+
+	output := buf.String()
+
+	if !strings.Contains(output, "CREATE UNIQUE INDEX") {
+		t.Error("Expected CREATE UNIQUE INDEX statement")
+	}
+}
+
+func TestQuoteIdentifier(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected string
+	}{
+		{"users", `"users"`},
+		{"public_users", `"public_users"`},
+		{`user"name`, `"user""name"`}, // Double quotes should be escaped
+	}
+
+	for _, tt := range tests {
+		result := QuoteIdentifier(tt.input)
+		if result != tt.expected {
+			t.Errorf("QuoteIdentifier(%q) = %q, want %q", tt.input, result, tt.expected)
+		}
+	}
+}