feat(ui): add relationship management features in schema editor

- Implement functionality to create, update, delete, and view relationships between tables.
- Introduce new UI screens for managing relationships, including forms for adding and editing relationships.
- Enhance table editor with navigation to relationship management.
- Ensure relationships are displayed in a structured table format for better usability.

pkg/commontypes/doc.go

@@ -0,0 +1,28 @@
+// Package commontypes provides shared type definitions used across multiple packages.
+//
+// # Overview
+//
+// The commontypes package contains common data structures, constants, and type
+// definitions that are shared between different parts of RelSpec but don't belong
+// to the core models package.
+//
+// # Purpose
+//
+// This package helps avoid circular dependencies by providing a common location
+// for types that are used by multiple packages without creating import cycles.
+//
+// # Contents
+//
+// Common types may include:
+//   - Shared enums and constants
+//   - Utility type aliases
+//   - Common error types
+//   - Shared configuration structures
+//
+// # Usage
+//
+//	import "git.warky.dev/wdevs/relspecgo/pkg/commontypes"
+//
+//	// Use common types
+//	var formatType commontypes.FormatType
+package commontypes

pkg/diff/doc.go

@@ -0,0 +1,43 @@
+// Package diff provides utilities for comparing database schemas and identifying differences.
+//
+// # Overview
+//
+// The diff package compares two database models at various granularity levels (database,
+// schema, table, column) and produces detailed reports of differences including:
+//   - Missing items (present in source but not in target)
+//   - Extra items (present in target but not in source)
+//   - Modified items (present in both but with different properties)
+//
+// # Usage
+//
+// Compare two databases and format the output:
+//
+//	result := diff.CompareDatabases(sourceDB, targetDB)
+//	err := diff.FormatDiff(result, diff.OutputFormatText, os.Stdout)
+//
+// # Output Formats
+//
+// The package supports multiple output formats:
+//   - OutputFormatText: Human-readable text format
+//   - OutputFormatJSON: Structured JSON output
+//   - OutputFormatYAML: Structured YAML output
+//
+// # Comparison Scope
+//
+// The comparison covers:
+//   - Schemas: Name, description, and contents
+//   - Tables: Name, description, and all sub-elements
+//   - Columns: Type, nullability, defaults, constraints
+//   - Indexes: Columns, uniqueness, type
+//   - Constraints: Type, columns, references
+//   - Relationships: Type, from/to tables and columns
+//   - Views: Definition and columns
+//   - Sequences: Start value, increment, min/max values
+//
+// # Use Cases
+//
+//   - Schema migration planning
+//   - Database synchronization verification
+//   - Change tracking and auditing
+//   - CI/CD pipeline validation
+package diff

pkg/inspector/doc.go

@@ -0,0 +1,40 @@
+// Package inspector provides database introspection capabilities for live databases.
+//
+// # Overview
+//
+// The inspector package contains utilities for connecting to live databases and
+// extracting their schema information through system catalog queries and metadata
+// inspection.
+//
+// # Features
+//
+//   - Database connection management
+//   - Schema metadata extraction
+//   - Table structure analysis
+//   - Constraint and index discovery
+//   - Foreign key relationship mapping
+//
+// # Supported Databases
+//
+//   - PostgreSQL (via pgx driver)
+//   - SQLite (via modernc.org/sqlite driver)
+//
+// # Usage
+//
+// This package is used internally by database readers (pgsql, sqlite) to perform
+// live schema introspection:
+//
+//	inspector := inspector.NewPostgreSQLInspector(connString)
+//	schemas, err := inspector.GetSchemas()
+//	tables, err := inspector.GetTables(schemaName)
+//
+// # Architecture
+//
+// Each database type has its own inspector implementation that understands the
+// specific system catalogs and metadata structures of that database system.
+//
+// # Security
+//
+// Inspectors use read-only operations and never modify database structure.
+// Connection credentials should be handled securely.
+package inspector

pkg/pgsql/doc.go

@@ -0,0 +1,36 @@
+// Package pgsql provides PostgreSQL-specific utilities and helpers.
+//
+// # Overview
+//
+// The pgsql package contains PostgreSQL-specific functionality including:
+//   - SQL reserved keyword validation
+//   - Data type mappings and conversions
+//   - PostgreSQL-specific schema introspection helpers
+//
+// # Components
+//
+// keywords.go - SQL reserved keywords validation
+//
+//	Provides functions to check if identifiers conflict with SQL reserved words
+//	and need quoting for safe usage in PostgreSQL queries.
+//
+// datatypes.go - PostgreSQL data type utilities
+//
+//	Contains mappings between PostgreSQL data types and their equivalents in other
+//	systems, as well as type conversion and normalization functions.
+//
+// # Usage
+//
+//	// Check if identifier needs quoting
+//	if pgsql.IsReservedKeyword("user") {
+//	    // Quote the identifier
+//	}
+//
+//	// Normalize data type
+//	normalizedType := pgsql.NormalizeDataType("varchar(255)")
+//
+// # Purpose
+//
+// This package supports the PostgreSQL reader and writer implementations by providing
+// shared utilities for handling PostgreSQL-specific schema elements and constraints.
+package pgsql

pkg/readers/doc.go

@@ -0,0 +1,53 @@
+// Package readers provides interfaces and implementations for reading database schemas
+// from various input formats and data sources.
+//
+// # Overview
+//
+// The readers package defines a common Reader interface that all format-specific readers
+// implement. This allows RelSpec to read database schemas from multiple sources including:
+//   - Live databases (PostgreSQL, SQLite)
+//   - Schema definition files (DBML, DCTX, DrawDB, GraphQL)
+//   - ORM model files (GORM, Bun, Drizzle, Prisma, TypeORM)
+//   - Data interchange formats (JSON, YAML)
+//
+// # Architecture
+//
+// Each reader implementation is located in its own subpackage (e.g., pkg/readers/dbml,
+// pkg/readers/pgsql) and implements the Reader interface, supporting three levels of
+// granularity:
+//   - ReadDatabase() - Read complete database with all schemas
+//   - ReadSchema() - Read single schema with all tables
+//   - ReadTable() - Read single table with all columns and metadata
+//
+// # Usage
+//
+// Readers are instantiated with ReaderOptions containing source-specific configuration:
+//
+//	// Read from file
+//	reader := dbml.NewReader(&readers.ReaderOptions{
+//	    FilePath: "schema.dbml",
+//	})
+//	db, err := reader.ReadDatabase()
+//
+//	// Read from database
+//	reader := pgsql.NewReader(&readers.ReaderOptions{
+//	    ConnectionString: "postgres://user:pass@localhost/mydb",
+//	})
+//	db, err := reader.ReadDatabase()
+//
+// # Supported Formats
+//
+//   - dbml: Database Markup Language files
+//   - dctx: DCTX schema files
+//   - drawdb: DrawDB JSON format
+//   - graphql: GraphQL schema definition language
+//   - json: JSON database schema
+//   - yaml: YAML database schema
+//   - gorm: Go GORM model structs
+//   - bun: Go Bun model structs
+//   - drizzle: TypeScript Drizzle ORM schemas
+//   - prisma: Prisma schema language
+//   - typeorm: TypeScript TypeORM entities
+//   - pgsql: PostgreSQL live database introspection
+//   - sqlite: SQLite database files
+package readers

pkg/readers/sqlite/queries.go

@@ -106,7 +106,7 @@ func (r *Reader) queryColumns(tableName string) (map[string]*models.Column, erro
 		}
 
 		// Check for autoincrement (SQLite uses INTEGER PRIMARY KEY AUTOINCREMENT)
-		if pk > 0 && strings.ToUpper(dataType) == "INTEGER" {
+		if pk > 0 && strings.EqualFold(dataType, "INTEGER") {
 			column.AutoIncrement = r.isAutoIncrement(tableName, name)
 		}
 

pkg/readers/sqlite/reader.go

@@ -187,35 +187,35 @@ func (r *Reader) close() {
 func (r *Reader) mapDataType(sqliteType string) string {
 	// SQLite has a flexible type system, but we map common types
 	typeMap := map[string]string{
-		"INTEGER":  "int",
-		"INT":      "int",
-		"TINYINT":  "int8",
-		"SMALLINT": "int16",
-		"MEDIUMINT": "int",
-		"BIGINT":   "int64",
-		"UNSIGNED BIG INT": "uint64",
-		"INT2":     "int16",
-		"INT8":     "int64",
-		"REAL":     "float64",
-		"DOUBLE":   "float64",
-		"DOUBLE PRECISION": "float64",
-		"FLOAT":    "float32",
-		"NUMERIC":  "decimal",
-		"DECIMAL":  "decimal",
-		"BOOLEAN":  "bool",
-		"BOOL":     "bool",
-		"DATE":     "date",
-		"DATETIME": "timestamp",
-		"TIMESTAMP": "timestamp",
-		"TEXT":     "string",
-		"VARCHAR":  "string",
-		"CHAR":     "string",
-		"CHARACTER": "string",
+		"INTEGER":           "int",
+		"INT":               "int",
+		"TINYINT":           "int8",
+		"SMALLINT":          "int16",
+		"MEDIUMINT":         "int",
+		"BIGINT":            "int64",
+		"UNSIGNED BIG INT":  "uint64",
+		"INT2":              "int16",
+		"INT8":              "int64",
+		"REAL":              "float64",
+		"DOUBLE":            "float64",
+		"DOUBLE PRECISION":  "float64",
+		"FLOAT":             "float32",
+		"NUMERIC":           "decimal",
+		"DECIMAL":           "decimal",
+		"BOOLEAN":           "bool",
+		"BOOL":              "bool",
+		"DATE":              "date",
+		"DATETIME":          "timestamp",
+		"TIMESTAMP":         "timestamp",
+		"TEXT":              "string",
+		"VARCHAR":           "string",
+		"CHAR":              "string",
+		"CHARACTER":         "string",
 		"VARYING CHARACTER": "string",
-		"NCHAR":    "string",
-		"NVARCHAR": "string",
-		"CLOB":     "text",
-		"BLOB":     "bytea",
+		"NCHAR":             "string",
+		"NVARCHAR":          "string",
+		"CLOB":              "text",
+		"BLOB":              "bytea",
 	}
 
 	// Try exact match first

pkg/reflectutil/doc.go

@@ -0,0 +1,36 @@
+// Package reflectutil provides reflection utilities for analyzing Go code structures.
+//
+// # Overview
+//
+// The reflectutil package offers helper functions for working with Go's reflection
+// capabilities, particularly for parsing Go struct definitions and extracting type
+// information. This is used by readers that parse ORM model files.
+//
+// # Features
+//
+//   - Struct tag parsing and extraction
+//   - Type information analysis
+//   - Field metadata extraction
+//   - ORM tag interpretation (GORM, Bun, etc.)
+//
+// # Usage
+//
+// This package is primarily used internally by readers like GORM and Bun to parse
+// Go struct definitions and convert them to database schema models.
+//
+//	// Example: Parse struct tags
+//	tags := reflectutil.ParseStructTags(field)
+//	columnName := tags.Get("db")
+//
+// # Supported ORM Tags
+//
+// The package understands tag conventions from:
+//   - GORM (gorm tag)
+//   - Bun (bun tag)
+//   - Standard database/sql (db tag)
+//
+// # Purpose
+//
+// This package enables RelSpec to read existing ORM models and convert them to
+// a unified schema representation for transformation to other formats.
+package reflectutil

pkg/transform/doc.go

@@ -0,0 +1,34 @@
+// Package transform provides validation and transformation utilities for database models.
+//
+// # Overview
+//
+// The transform package contains a Transformer type that provides methods for validating
+// and normalizing database schemas. It ensures schema correctness and consistency across
+// different format conversions.
+//
+// # Features
+//
+//   - Database validation (structure and naming conventions)
+//   - Schema validation (completeness and integrity)
+//   - Table validation (column definitions and constraints)
+//   - Data type normalization
+//
+// # Usage
+//
+//	transformer := transform.NewTransformer()
+//	err := transformer.ValidateDatabase(db)
+//	if err != nil {
+//	    log.Fatal("Invalid database schema:", err)
+//	}
+//
+// # Validation Scope
+//
+// The transformer validates:
+//   - Required fields presence
+//   - Naming convention adherence
+//   - Data type compatibility
+//   - Constraint consistency
+//   - Relationship integrity
+//
+// Note: Some validation methods are currently stubs and will be implemented as needed.
+package transform

pkg/ui/doc.go

@@ -0,0 +1,57 @@
+// Package ui provides an interactive terminal user interface (TUI) for editing database schemas.
+//
+// # Overview
+//
+// The ui package implements a full-featured terminal-based schema editor using tview,
+// allowing users to visually create, modify, and manage database schemas without writing
+// code or SQL.
+//
+// # Features
+//
+// The schema editor supports:
+//   - Database management: Edit name, description, and properties
+//   - Schema management: Create, edit, delete schemas
+//   - Table management: Create, edit, delete tables
+//   - Column management: Add, modify, delete columns with full property support
+//   - Relationship management: Define and edit table relationships
+//   - Domain management: Organize tables into logical domains
+//   - Import & merge: Combine schemas from multiple sources
+//   - Save: Export to any supported format
+//
+// # Architecture
+//
+// The package is organized into several components:
+//   - editor.go: Main editor and application lifecycle
+//   - *_screens.go: UI screens for each entity type
+//   - *_dataops.go: Business logic and data operations
+//   - dialogs.go: Reusable dialog components
+//   - load_save_screens.go: File I/O and format selection
+//   - main_menu.go: Primary navigation menu
+//
+// # Usage
+//
+//	editor := ui.NewSchemaEditor(database)
+//	if err := editor.Run(); err != nil {
+//	    log.Fatal(err)
+//	}
+//
+// Or with pre-configured load/save options:
+//
+//	editor := ui.NewSchemaEditorWithConfigs(database, loadConfig, saveConfig)
+//	if err := editor.Run(); err != nil {
+//	    log.Fatal(err)
+//	}
+//
+// # Navigation
+//
+//   - Arrow keys: Navigate between items
+//   - Enter: Select/edit item
+//   - Tab/Shift+Tab: Navigate between buttons
+//   - Escape: Go back/cancel
+//   - Letter shortcuts: Quick actions (e.g., 'n' for new, 'e' for edit, 'd' for delete)
+//
+// # Integration
+//
+// The editor integrates with all readers and writers, supporting load/save operations
+// for any format supported by RelSpec (DBML, PostgreSQL, GORM, Prisma, etc.).
+package ui

pkg/ui/relation_dataops.go

@@ -0,0 +1,115 @@
+package ui
+
+import "git.warky.dev/wdevs/relspecgo/pkg/models"
+
+// Relationship data operations - business logic for relationship management
+
+// CreateRelationship creates a new relationship and adds it to a table
+func (se *SchemaEditor) CreateRelationship(schemaIndex, tableIndex int, rel *models.Relationship) *models.Relationship {
+	if schemaIndex < 0 || schemaIndex >= len(se.db.Schemas) {
+		return nil
+	}
+
+	schema := se.db.Schemas[schemaIndex]
+	if tableIndex < 0 || tableIndex >= len(schema.Tables) {
+		return nil
+	}
+
+	table := schema.Tables[tableIndex]
+	if table.Relationships == nil {
+		table.Relationships = make(map[string]*models.Relationship)
+	}
+
+	table.Relationships[rel.Name] = rel
+	table.UpdateDate()
+	return rel
+}
+
+// UpdateRelationship updates an existing relationship
+func (se *SchemaEditor) UpdateRelationship(schemaIndex, tableIndex int, oldName string, rel *models.Relationship) bool {
+	if schemaIndex < 0 || schemaIndex >= len(se.db.Schemas) {
+		return false
+	}
+
+	schema := se.db.Schemas[schemaIndex]
+	if tableIndex < 0 || tableIndex >= len(schema.Tables) {
+		return false
+	}
+
+	table := schema.Tables[tableIndex]
+	if table.Relationships == nil {
+		return false
+	}
+
+	// Delete old entry if name changed
+	if oldName != rel.Name {
+		delete(table.Relationships, oldName)
+	}
+
+	table.Relationships[rel.Name] = rel
+	table.UpdateDate()
+	return true
+}
+
+// DeleteRelationship removes a relationship from a table
+func (se *SchemaEditor) DeleteRelationship(schemaIndex, tableIndex int, relName string) bool {
+	if schemaIndex < 0 || schemaIndex >= len(se.db.Schemas) {
+		return false
+	}
+
+	schema := se.db.Schemas[schemaIndex]
+	if tableIndex < 0 || tableIndex >= len(schema.Tables) {
+		return false
+	}
+
+	table := schema.Tables[tableIndex]
+	if table.Relationships == nil {
+		return false
+	}
+
+	delete(table.Relationships, relName)
+	table.UpdateDate()
+	return true
+}
+
+// GetRelationship returns a relationship by name
+func (se *SchemaEditor) GetRelationship(schemaIndex, tableIndex int, relName string) *models.Relationship {
+	if schemaIndex < 0 || schemaIndex >= len(se.db.Schemas) {
+		return nil
+	}
+
+	schema := se.db.Schemas[schemaIndex]
+	if tableIndex < 0 || tableIndex >= len(schema.Tables) {
+		return nil
+	}
+
+	table := schema.Tables[tableIndex]
+	if table.Relationships == nil {
+		return nil
+	}
+
+	return table.Relationships[relName]
+}
+
+// GetRelationshipNames returns all relationship names for a table
+func (se *SchemaEditor) GetRelationshipNames(schemaIndex, tableIndex int) []string {
+	if schemaIndex < 0 || schemaIndex >= len(se.db.Schemas) {
+		return nil
+	}
+
+	schema := se.db.Schemas[schemaIndex]
+	if tableIndex < 0 || tableIndex >= len(schema.Tables) {
+		return nil
+	}
+
+	table := schema.Tables[tableIndex]
+	if table.Relationships == nil {
+		return nil
+	}
+
+	names := make([]string, 0, len(table.Relationships))
+	for name := range table.Relationships {
+		names = append(names, name)
+	}
+	return names
+}

pkg/ui/relation_screens.go

@@ -0,0 +1,486 @@
+package ui
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/gdamore/tcell/v2"
+	"github.com/rivo/tview"
+
+	"git.warky.dev/wdevs/relspecgo/pkg/models"
+)
+
+// showRelationshipList displays all relationships for a table
+func (se *SchemaEditor) showRelationshipList(schemaIndex, tableIndex int) {
+	table := se.GetTable(schemaIndex, tableIndex)
+	if table == nil {
+		return
+	}
+
+	flex := tview.NewFlex().SetDirection(tview.FlexRow)
+
+	// Title
+	title := tview.NewTextView().
+		SetText(fmt.Sprintf("[::b]Relationships for Table: %s", table.Name)).
+		SetDynamicColors(true).
+		SetTextAlign(tview.AlignCenter)
+
+	// Create relationships table
+	relTable := tview.NewTable().SetBorders(true).SetSelectable(true, false).SetFixed(1, 0)
+
+	// Add header row
+	headers := []string{"Name", "Type", "From Columns", "To Table", "To Columns", "Description"}
+	headerWidths := []int{20, 15, 20, 20, 20}
+	for i, header := range headers {
+		padding := ""
+		if i < len(headerWidths) {
+			padding = strings.Repeat(" ", headerWidths[i]-len(header))
+		}
+		cell := tview.NewTableCell(header + padding).
+			SetTextColor(tcell.ColorYellow).
+			SetSelectable(false).
+			SetAlign(tview.AlignLeft)
+		relTable.SetCell(0, i, cell)
+	}
+
+	// Get relationship names
+	relNames := se.GetRelationshipNames(schemaIndex, tableIndex)
+	for row, relName := range relNames {
+		rel := table.Relationships[relName]
+
+		// Name
+		nameStr := fmt.Sprintf("%-20s", rel.Name)
+		nameCell := tview.NewTableCell(nameStr).SetSelectable(true)
+		relTable.SetCell(row+1, 0, nameCell)
+
+		// Type
+		typeStr := fmt.Sprintf("%-15s", string(rel.Type))
+		typeCell := tview.NewTableCell(typeStr).SetSelectable(true)
+		relTable.SetCell(row+1, 1, typeCell)
+
+		// From Columns
+		fromColsStr := strings.Join(rel.FromColumns, ", ")
+		fromColsStr = fmt.Sprintf("%-20s", fromColsStr)
+		fromColsCell := tview.NewTableCell(fromColsStr).SetSelectable(true)
+		relTable.SetCell(row+1, 2, fromColsCell)
+
+		// To Table
+		toTableStr := rel.ToTable
+		if rel.ToSchema != "" && rel.ToSchema != table.Schema {
+			toTableStr = rel.ToSchema + "." + rel.ToTable
+		}
+		toTableStr = fmt.Sprintf("%-20s", toTableStr)
+		toTableCell := tview.NewTableCell(toTableStr).SetSelectable(true)
+		relTable.SetCell(row+1, 3, toTableCell)
+
+		// To Columns
+		toColsStr := strings.Join(rel.ToColumns, ", ")
+		toColsStr = fmt.Sprintf("%-20s", toColsStr)
+		toColsCell := tview.NewTableCell(toColsStr).SetSelectable(true)
+		relTable.SetCell(row+1, 4, toColsCell)
+
+		// Description
+		descCell := tview.NewTableCell(rel.Description).SetSelectable(true)
+		relTable.SetCell(row+1, 5, descCell)
+	}
+
+	relTable.SetTitle(" Relationships ").SetBorder(true).SetTitleAlign(tview.AlignLeft)
+
+	// Action buttons
+	btnFlex := tview.NewFlex()
+	btnNew := tview.NewButton("New Relationship [n]").SetSelectedFunc(func() {
+		se.showNewRelationshipDialog(schemaIndex, tableIndex)
+	})
+	btnEdit := tview.NewButton("Edit [e]").SetSelectedFunc(func() {
+		row, _ := relTable.GetSelection()
+		if row > 0 && row <= len(relNames) {
+			relName := relNames[row-1]
+			se.showEditRelationshipDialog(schemaIndex, tableIndex, relName)
+		}
+	})
+	btnDelete := tview.NewButton("Delete [d]").SetSelectedFunc(func() {
+		row, _ := relTable.GetSelection()
+		if row > 0 && row <= len(relNames) {
+			relName := relNames[row-1]
+			se.showDeleteRelationshipConfirm(schemaIndex, tableIndex, relName)
+		}
+	})
+	btnBack := tview.NewButton("Back [b]").SetSelectedFunc(func() {
+		se.pages.RemovePage("relationships")
+		se.pages.SwitchToPage("table-editor")
+	})
+
+	// Set up button navigation
+	btnNew.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
+		if event.Key() == tcell.KeyBacktab {
+			se.app.SetFocus(relTable)
+			return nil
+		}
+		if event.Key() == tcell.KeyTab {
+			se.app.SetFocus(btnEdit)
+			return nil
+		}
+		return event
+	})
+
+	btnEdit.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
+		if event.Key() == tcell.KeyBacktab {
+			se.app.SetFocus(btnNew)
+			return nil
+		}
+		if event.Key() == tcell.KeyTab {
+			se.app.SetFocus(btnDelete)
+			return nil
+		}
+		return event
+	})
+
+	btnDelete.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
+		if event.Key() == tcell.KeyBacktab {
+			se.app.SetFocus(btnEdit)
+			return nil
+		}
+		if event.Key() == tcell.KeyTab {
+			se.app.SetFocus(btnBack)
+			return nil
+		}
+		return event
+	})
+
+	btnBack.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
+		if event.Key() == tcell.KeyBacktab {
+			se.app.SetFocus(btnDelete)
+			return nil
+		}
+		if event.Key() == tcell.KeyTab {
+			se.app.SetFocus(relTable)
+			return nil
+		}
+		return event
+	})
+
+	btnFlex.AddItem(btnNew, 0, 1, true).
+		AddItem(btnEdit, 0, 1, false).
+		AddItem(btnDelete, 0, 1, false).
+		AddItem(btnBack, 0, 1, false)
+
+	relTable.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
+		if event.Key() == tcell.KeyEscape {
+			se.pages.RemovePage("relationships")
+			se.pages.SwitchToPage("table-editor")
+			return nil
+		}
+		if event.Key() == tcell.KeyTab {
+			se.app.SetFocus(btnNew)
+			return nil
+		}
+		if event.Key() == tcell.KeyEnter {
+			row, _ := relTable.GetSelection()
+			if row > 0 && row <= len(relNames) {
+				relName := relNames[row-1]
+				se.showEditRelationshipDialog(schemaIndex, tableIndex, relName)
+			}
+			return nil
+		}
+		if event.Rune() == 'n' {
+			se.showNewRelationshipDialog(schemaIndex, tableIndex)
+			return nil
+		}
+		if event.Rune() == 'e' {
+			row, _ := relTable.GetSelection()
+			if row > 0 && row <= len(relNames) {
+				relName := relNames[row-1]
+				se.showEditRelationshipDialog(schemaIndex, tableIndex, relName)
+			}
+			return nil
+		}
+		if event.Rune() == 'd' {
+			row, _ := relTable.GetSelection()
+			if row > 0 && row <= len(relNames) {
+				relName := relNames[row-1]
+				se.showDeleteRelationshipConfirm(schemaIndex, tableIndex, relName)
+			}
+			return nil
+		}
+		if event.Rune() == 'b' {
+			se.pages.RemovePage("relationships")
+			se.pages.SwitchToPage("table-editor")
+			return nil
+		}
+		return event
+	})
+
+	flex.AddItem(title, 1, 0, false).
+		AddItem(relTable, 0, 1, true).
+		AddItem(btnFlex, 1, 0, false)
+
+	se.pages.AddPage("relationships", flex, true, true)
+}
+
+// showNewRelationshipDialog shows dialog to create a new relationship
+func (se *SchemaEditor) showNewRelationshipDialog(schemaIndex, tableIndex int) {
+	table := se.GetTable(schemaIndex, tableIndex)
+	if table == nil {
+		return
+	}
+
+	form := tview.NewForm()
+
+	// Collect all tables for dropdown
+	var allTables []string
+	var tableMap []struct{ schemaIdx, tableIdx int }
+	for si, schema := range se.db.Schemas {
+		for ti, t := range schema.Tables {
+			tableName := t.Name
+			if schema.Name != table.Schema {
+				tableName = schema.Name + "." + t.Name
+			}
+			allTables = append(allTables, tableName)
+			tableMap = append(tableMap, struct{ schemaIdx, tableIdx int }{si, ti})
+		}
+	}
+
+	relName := ""
+	relType := models.OneToMany
+	fromColumns := ""
+	toColumns := ""
+	description := ""
+	selectedTableIdx := 0
+
+	form.AddInputField("Name", "", 40, nil, func(value string) {
+		relName = value
+	})
+
+	form.AddDropDown("Type", []string{
+		string(models.OneToOne),
+		string(models.OneToMany),
+		string(models.ManyToMany),
+	}, 1, func(option string, optionIndex int) {
+		relType = models.RelationType(option)
+	})
+
+	form.AddInputField("From Columns (comma-separated)", "", 40, nil, func(value string) {
+		fromColumns = value
+	})
+
+	form.AddDropDown("To Table", allTables, 0, func(option string, optionIndex int) {
+		selectedTableIdx = optionIndex
+	})
+
+	form.AddInputField("To Columns (comma-separated)", "", 40, nil, func(value string) {
+		toColumns = value
+	})
+
+	form.AddInputField("Description", "", 60, nil, func(value string) {
+		description = value
+	})
+
+	form.AddButton("Save", func() {
+		if relName == "" {
+			return
+		}
+
+		// Parse columns
+		fromCols := strings.Split(fromColumns, ",")
+		for i := range fromCols {
+			fromCols[i] = strings.TrimSpace(fromCols[i])
+		}
+
+		toCols := strings.Split(toColumns, ",")
+		for i := range toCols {
+			toCols[i] = strings.TrimSpace(toCols[i])
+		}
+
+		// Get target table
+		targetSchema := se.db.Schemas[tableMap[selectedTableIdx].schemaIdx]
+		targetTable := targetSchema.Tables[tableMap[selectedTableIdx].tableIdx]
+
+		rel := models.InitRelationship(relName, relType)
+		rel.FromTable = table.Name
+		rel.FromSchema = table.Schema
+		rel.FromColumns = fromCols
+		rel.ToTable = targetTable.Name
+		rel.ToSchema = targetTable.Schema
+		rel.ToColumns = toCols
+		rel.Description = description
+
+		se.CreateRelationship(schemaIndex, tableIndex, rel)
+
+		se.pages.RemovePage("new-relationship")
+		se.pages.RemovePage("relationships")
+		se.showRelationshipList(schemaIndex, tableIndex)
+	})
+
+	form.AddButton("Back", func() {
+		se.pages.RemovePage("new-relationship")
+	})
+
+	form.SetBorder(true).SetTitle(" New Relationship ").SetTitleAlign(tview.AlignLeft)
+	form.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
+		if event.Key() == tcell.KeyEscape {
+			se.pages.RemovePage("new-relationship")
+			return nil
+		}
+		return event
+	})
+
+	se.pages.AddPage("new-relationship", form, true, true)
+}
+
+// showEditRelationshipDialog shows dialog to edit a relationship
+func (se *SchemaEditor) showEditRelationshipDialog(schemaIndex, tableIndex int, relName string) {
+	table := se.GetTable(schemaIndex, tableIndex)
+	if table == nil {
+		return
+	}
+
+	rel := se.GetRelationship(schemaIndex, tableIndex, relName)
+	if rel == nil {
+		return
+	}
+
+	form := tview.NewForm()
+
+	// Collect all tables for dropdown
+	var allTables []string
+	var tableMap []struct{ schemaIdx, tableIdx int }
+	selectedTableIdx := 0
+	for si, schema := range se.db.Schemas {
+		for ti, t := range schema.Tables {
+			tableName := t.Name
+			if schema.Name != table.Schema {
+				tableName = schema.Name + "." + t.Name
+			}
+			allTables = append(allTables, tableName)
+			tableMap = append(tableMap, struct{ schemaIdx, tableIdx int }{si, ti})
+
+			// Check if this is the current target table
+			if t.Name == rel.ToTable && schema.Name == rel.ToSchema {
+				selectedTableIdx = len(allTables) - 1
+			}
+		}
+	}
+
+	newName := rel.Name
+	relType := rel.Type
+	fromColumns := strings.Join(rel.FromColumns, ", ")
+	toColumns := strings.Join(rel.ToColumns, ", ")
+	description := rel.Description
+
+	form.AddInputField("Name", rel.Name, 40, nil, func(value string) {
+		newName = value
+	})
+
+	// Find initial type index
+	typeIdx := 1 // OneToMany default
+	typeOptions := []string{
+		string(models.OneToOne),
+		string(models.OneToMany),
+		string(models.ManyToMany),
+	}
+	for i, opt := range typeOptions {
+		if opt == string(rel.Type) {
+			typeIdx = i
+			break
+		}
+	}
+
+	form.AddDropDown("Type", typeOptions, typeIdx, func(option string, optionIndex int) {
+		relType = models.RelationType(option)
+	})
+
+	form.AddInputField("From Columns (comma-separated)", fromColumns, 40, nil, func(value string) {
+		fromColumns = value
+	})
+
+	form.AddDropDown("To Table", allTables, selectedTableIdx, func(option string, optionIndex int) {
+		selectedTableIdx = optionIndex
+	})
+
+	form.AddInputField("To Columns (comma-separated)", toColumns, 40, nil, func(value string) {
+		toColumns = value
+	})
+
+	form.AddInputField("Description", rel.Description, 60, nil, func(value string) {
+		description = value
+	})
+
+	form.AddButton("Save", func() {
+		if newName == "" {
+			return
+		}
+
+		// Parse columns
+		fromCols := strings.Split(fromColumns, ",")
+		for i := range fromCols {
+			fromCols[i] = strings.TrimSpace(fromCols[i])
+		}
+
+		toCols := strings.Split(toColumns, ",")
+		for i := range toCols {
+			toCols[i] = strings.TrimSpace(toCols[i])
+		}
+
+		// Get target table
+		targetSchema := se.db.Schemas[tableMap[selectedTableIdx].schemaIdx]
+		targetTable := targetSchema.Tables[tableMap[selectedTableIdx].tableIdx]
+
+		updatedRel := models.InitRelationship(newName, relType)
+		updatedRel.FromTable = table.Name
+		updatedRel.FromSchema = table.Schema
+		updatedRel.FromColumns = fromCols
+		updatedRel.ToTable = targetTable.Name
+		updatedRel.ToSchema = targetTable.Schema
+		updatedRel.ToColumns = toCols
+		updatedRel.Description = description
+		updatedRel.GUID = rel.GUID
+
+		se.UpdateRelationship(schemaIndex, tableIndex, relName, updatedRel)
+
+		se.pages.RemovePage("edit-relationship")
+		se.pages.RemovePage("relationships")
+		se.showRelationshipList(schemaIndex, tableIndex)
+	})
+
+	form.AddButton("Back", func() {
+		se.pages.RemovePage("edit-relationship")
+	})
+
+	form.SetBorder(true).SetTitle(" Edit Relationship ").SetTitleAlign(tview.AlignLeft)
+	form.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
+		if event.Key() == tcell.KeyEscape {
+			se.pages.RemovePage("edit-relationship")
+			return nil
+		}
+		return event
+	})
+
+	se.pages.AddPage("edit-relationship", form, true, true)
+}
+
+// showDeleteRelationshipConfirm shows confirmation dialog for deleting a relationship
+func (se *SchemaEditor) showDeleteRelationshipConfirm(schemaIndex, tableIndex int, relName string) {
+	modal := tview.NewModal().
+		SetText(fmt.Sprintf("Delete relationship '%s'? This action cannot be undone.", relName)).
+		AddButtons([]string{"Cancel", "Delete"}).
+		SetDoneFunc(func(buttonIndex int, buttonLabel string) {
+			if buttonLabel == "Delete" {
+				se.DeleteRelationship(schemaIndex, tableIndex, relName)
+				se.pages.RemovePage("delete-relationship-confirm")
+				se.pages.RemovePage("relationships")
+				se.showRelationshipList(schemaIndex, tableIndex)
+			} else {
+				se.pages.RemovePage("delete-relationship-confirm")
+			}
+		})
+
+	modal.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
+		if event.Key() == tcell.KeyEscape {
+			se.pages.RemovePage("delete-relationship-confirm")
+			return nil
+		}
+		return event
+	})
+
+	se.pages.AddAndSwitchToPage("delete-relationship-confirm", modal, true)
+}

pkg/ui/table_screens.go

@@ -270,6 +270,9 @@ func (se *SchemaEditor) showTableEditor(schemaIndex, tableIndex int, table *mode
 			se.showColumnEditor(schemaIndex, tableIndex, row-1, column)
 		}
 	})
+	btnRelations := tview.NewButton("Relations [r]").SetSelectedFunc(func() {
+		se.showRelationshipList(schemaIndex, tableIndex)
+	})
 	btnDelTable := tview.NewButton("Delete Table [d]").SetSelectedFunc(func() {
 		se.showDeleteTableConfirm(schemaIndex, tableIndex)
 	})
@@ -308,6 +311,18 @@ func (se *SchemaEditor) showTableEditor(schemaIndex, tableIndex int, table *mode
 			se.app.SetFocus(btnEditColumn)
 			return nil
 		}
+		if event.Key() == tcell.KeyTab {
+			se.app.SetFocus(btnRelations)
+			return nil
+		}
+		return event
+	})
+
+	btnRelations.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
+		if event.Key() == tcell.KeyBacktab {
+			se.app.SetFocus(btnEditTable)
+			return nil
+		}
 		if event.Key() == tcell.KeyTab {
 			se.app.SetFocus(btnDelTable)
 			return nil
@@ -317,7 +332,7 @@ func (se *SchemaEditor) showTableEditor(schemaIndex, tableIndex int, table *mode
 
 	btnDelTable.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
 		if event.Key() == tcell.KeyBacktab {
-			se.app.SetFocus(btnEditTable)
+			se.app.SetFocus(btnRelations)
 			return nil
 		}
 		if event.Key() == tcell.KeyTab {
@@ -342,6 +357,7 @@ func (se *SchemaEditor) showTableEditor(schemaIndex, tableIndex int, table *mode
 	btnFlex.AddItem(btnNewCol, 0, 1, true).
 		AddItem(btnEditColumn, 0, 1, false).
 		AddItem(btnEditTable, 0, 1, false).
+		AddItem(btnRelations, 0, 1, false).
 		AddItem(btnDelTable, 0, 1, false).
 		AddItem(btnBack, 0, 1, false)
 
@@ -373,6 +389,10 @@ func (se *SchemaEditor) showTableEditor(schemaIndex, tableIndex int, table *mode
 			}
 			return nil
 		}
+		if event.Rune() == 'r' {
+			se.showRelationshipList(schemaIndex, tableIndex)
+			return nil
+		}
 		if event.Rune() == 'b' {
 			se.pages.RemovePage("table-editor")
 			se.pages.SwitchToPage("schema-editor")

pkg/writers/doc.go

@@ -0,0 +1,67 @@
+// Package writers provides interfaces and implementations for writing database schemas
+// to various output formats and destinations.
+//
+// # Overview
+//
+// The writers package defines a common Writer interface that all format-specific writers
+// implement. This allows RelSpec to export database schemas to multiple formats including:
+//   - SQL schema files (PostgreSQL, SQLite)
+//   - Schema definition files (DBML, DCTX, DrawDB, GraphQL)
+//   - ORM model files (GORM, Bun, Drizzle, Prisma, TypeORM)
+//   - Data interchange formats (JSON, YAML)
+//
+// # Architecture
+//
+// Each writer implementation is located in its own subpackage (e.g., pkg/writers/dbml,
+// pkg/writers/pgsql) and implements the Writer interface, supporting three levels of
+// granularity:
+//   - WriteDatabase() - Write complete database with all schemas
+//   - WriteSchema() - Write single schema with all tables
+//   - WriteTable() - Write single table with all columns and metadata
+//
+// # Usage
+//
+// Writers are instantiated with WriterOptions containing destination-specific configuration:
+//
+//	// Write to file
+//	writer := dbml.NewWriter(&writers.WriterOptions{
+//	    OutputPath: "schema.dbml",
+//	})
+//	err := writer.WriteDatabase(db)
+//
+//	// Write ORM models with package name
+//	writer := gorm.NewWriter(&writers.WriterOptions{
+//	    OutputPath:  "./models",
+//	    PackageName: "models",
+//	})
+//	err := writer.WriteDatabase(db)
+//
+//	// Write with schema flattening for SQLite
+//	writer := sqlite.NewWriter(&writers.WriterOptions{
+//	    OutputPath:    "schema.sql",
+//	    FlattenSchema: true,
+//	})
+//	err := writer.WriteDatabase(db)
+//
+// # Schema Flattening
+//
+// The FlattenSchema option controls how schema-qualified table names are handled:
+//   - false (default): Uses dot notation (schema.table)
+//   - true: Joins with underscore (schema_table), useful for SQLite
+//
+// # Supported Formats
+//
+//   - dbml: Database Markup Language files
+//   - dctx: DCTX schema files
+//   - drawdb: DrawDB JSON format
+//   - graphql: GraphQL schema definition language
+//   - json: JSON database schema
+//   - yaml: YAML database schema
+//   - gorm: Go GORM model structs
+//   - bun: Go Bun model structs
+//   - drizzle: TypeScript Drizzle ORM schemas
+//   - prisma: Prisma schema language
+//   - typeorm: TypeScript TypeORM entities
+//   - pgsql: PostgreSQL SQL schema
+//   - sqlite: SQLite SQL schema with automatic flattening
+package writers