MSSQL: drop foreign key before dropping column

lib/dialects/mssql/query-generator.js

@@ -507,7 +507,7 @@ var QueryGenerator = {
       return '[' + identifier.replace(/[\[\]']+/g,'') + ']';
   },
 
-  getForeignKeysQuery: function(table, databaseName) {
+  getForeignKeysQuery: function(table) {
     var tableName = table.tableName || table;
     var sql = [
       'SELECT',
@@ -525,6 +525,27 @@ var QueryGenerator = {
     return sql;
   },
 
+  getForeignKeyQuery: function(table, attributeName) {
+    var tableName = table.tableName || table;
+    var sql = [
+      'SELECT',
+        'constraint_name = TC.CONSTRAINT_NAME',
+      'FROM',
+        'INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC',
+        'JOIN INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE CCU',
+          'ON TC.CONSTRAINT_NAME = CCU.CONSTRAINT_NAME',
+      "WHERE TC.CONSTRAINT_TYPE = 'FOREIGN KEY'",
+      'AND TC.TABLE_NAME =', wrapSingleQuote(tableName),
+      'AND CCU.COLUMN_NAME =', wrapSingleQuote(attributeName),
+    ].join(' ');
+
+    if (table.schema) {
+      sql += ' AND TC.TABLE_SCHEMA =' + wrapSingleQuote(table.schema);
+    }
+
+    return sql;
+  },
+
   dropForeignKeyQuery: function(tableName, foreignKey) {
     return Utils._.template('ALTER TABLE <%= table %> DROP <%= key %>')({
       table: this.quoteTable(tableName),

lib/dialects/mssql/query-interface.js

@@ -33,6 +33,18 @@ var removeColumn = function (tableName, attributeName, options) {
       return self.sequelize.query(dropConstraintSql, { raw: true, logging: options.logging});
     })
     .then(function () {
+      var findForeignKeySql = self.QueryGenerator.getForeignKeyQuery(tableName, attributeName);
+      return self.sequelize.query(findForeignKeySql , { raw: true, logging: options.logging});
+    })
+    .spread(function (results) {
+      if (!results.length) {
+        // No foreign key constraints found, so we can remove the column
+        return;
+      }
+      var dropForeignKeySql = self.QueryGenerator.dropForeignKeyQuery(tableName, results[0].constraint_name);
+      return self.sequelize.query(dropForeignKeySql , { raw: true, logging: options.logging});
+    })
+    .then(function () {
       var removeSql = self.QueryGenerator.removeColumnQuery(tableName, attributeName);
       return self.sequelize.query(removeSql, { raw: true, logging: options.logging});
     });