queries for getting and dropping foreign keys

lib/dialects/abstract/query-generator.js

@@ -354,8 +354,29 @@ module.exports = (function() {
       } else {
         return SqlString.escape(value, false, null, this.dialect, field)
       }
-    }
+    },
 
+    /**
+     * Generates an SQL query that returns all foreign keys of a table.
+     *
+     * @param  {String} tableName  The name of the table.
+     * @param  {String} schemaName The name of the schema.
+     * @return {String}            The generated sql query.
+     */
+    getForeignKeysQuery: function(tableName, schemaName) {
+      throwMethodUndefined('getForeignKeysQuery')
+    },
+
+    /**
+     * Generates an SQL query that removes a foreign key from a table.
+     *
+     * @param  {String} tableName  The name of the table.
+     * @param  {String} foreignKey The name of the foreign key constraint.
+     * @return {String}            The generated sql query.
+     */
+    dropForeignKeyQuery: function(tableName, foreignKey) {
+      throwMethodUndefined('dropForeignKeyQuery')
+    }
   }
 
   var throwMethodUndefined = function(methodName) {

lib/dialects/mysql/query-generator.js

@@ -595,6 +595,28 @@ module.exports = (function() {
 
     quoteIdentifiers: function(identifiers, force) {
       return identifiers.split('.').map(function(v) { return this.quoteIdentifier(v, force) }.bind(this)).join('.')
+    },
+
+    /**
+     * Generates an SQL query that returns all foreign keys of a table.
+     *
+     * @param  {String} tableName  The name of the table.
+     * @param  {String} schemaName The name of the schema.
+     * @return {String}            The generated sql query.
+     */
+    getForeignKeysQuery: function(tableName, schemaName) {
+      return "SELECT CONSTRAINT_NAME as constraint_name FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE where TABLE_NAME = '" + tableName + "' AND CONSTRAINT_NAME!='PRIMARY' AND CONSTRAINT_SCHEMA='" + schemaName + "' AND REFERENCED_TABLE_NAME IS NOT NULL;"
+    },
+
+    /**
+     * Generates an SQL query that removes a foreign key from a table.
+     *
+     * @param  {String} tableName  The name of the table.
+     * @param  {String} foreignKey The name of the foreign key constraint.
+     * @return {String}            The generated sql query.
+     */
+    dropForeignKeyQuery: function(tableName, foreignKey) {
+      return 'ALTER TABLE ' + this.quoteIdentifier(tableName) + ' DROP FOREIGN KEY ' + this.quoteIdentifier(foreignKey) + ';'
     }
   }
 

lib/dialects/postgres/query-generator.js

@@ -996,6 +996,28 @@ module.exports = (function() {
 
     quoteIdentifiers: function(identifiers, force) {
       return identifiers.split('.').map(function(t) { return this.quoteIdentifier(t, force) }.bind(this)).join('.')
+    },
+
+    /**
+     * Generates an SQL query that returns all foreign keys of a table.
+     *
+     * @param  {String} tableName  The name of the table.
+     * @param  {String} schemaName The name of the schema.
+     * @return {String}            The generated sql query.
+     */
+    getForeignKeysQuery: function(tableName, schemaName) {
+      return "SELECT conname as constraint_name, pg_catalog.pg_get_constraintdef(r.oid, true) as condef FROM pg_catalog.pg_constraint r WHERE r.conrelid = (SELECT oid FROM pg_class WHERE relname = '" + tableName + "' LIMIT 1) AND r.contype = 'f' ORDER BY 1;"
+    },
+
+    /**
+     * Generates an SQL query that removes a foreign key from a table.
+     *
+     * @param  {String} tableName  The name of the table.
+     * @param  {String} foreignKey The name of the foreign key constraint.
+     * @return {String}            The generated sql query.
+     */
+    dropForeignKeyQuery: function(tableName, foreignKey) {
+      return 'ALTER TABLE ' + this.quoteIdentifier(tableName) + ' DROP CONSTRAINT ' + this.quoteIdentifier(foreignKey) + ';'
     }
   }
 

lib/dialects/sqlite/query-generator.js

@@ -476,6 +476,17 @@ module.exports = (function() {
 
     quoteIdentifiers: function(identifiers, force) {
       return identifiers.split('.').map(function(v) { return this.quoteIdentifier(v, force) }.bind(this)).join('.')
+    },
+
+        /**
+     * Generates an SQL query that returns all foreign keys of a table.
+     *
+     * @param  {String} tableName  The name of the table.
+     * @param  {String} schemaName The name of the schema.
+     * @return {String}            The generated sql query.
+     */
+    getForeignKeysQuery: function(tableName, schemaName) {
+      return "PRAGMA foreign_key_list(\"" + tableName + "\")"
     }
   }