knex/lib/dialects/mssql/schema/compiler.js

// MySQL Schema Compiler
// -------
const { inherits } = require('util');
const SchemaCompiler = require('../../../schema/compiler');

function SchemaCompiler_MSSQL(client, builder) {
  SchemaCompiler.call(this, client, builder);
}
inherits(SchemaCompiler_MSSQL, SchemaCompiler);

Object.assign(SchemaCompiler_MSSQL.prototype, {
  dropTablePrefix: 'DROP TABLE ',
  dropTableIfExists(tableName) {
    const name = this.formatter.wrap(prefixedTableName(this.schema, tableName));
    this.pushQuery(
      `if object_id('${name}', 'U') is not null DROP TABLE ${name}`
    );
  },

  // Rename a table on the schema.
  renameTable(tableName, to) {
    this.pushQuery(
      `exec sp_rename ${this.formatter.parameter(
        prefixedTableName(this.schema, tableName)
      )}, ${this.formatter.parameter(to)}`
    );
  },

  // Check whether a table exists on the query.
  hasTable(tableName) {
    const formattedTable = this.formatter.parameter(
      this.formatter.wrap(prefixedTableName(this.schema, tableName))
    );

    const sql =
      `select object_id from sys.tables ` +
      `where object_id = object_id(${formattedTable})`;
    this.pushQuery({ sql, output: (resp) => resp.length > 0 });
  },

  // Check whether a column exists on the schema.
  hasColumn(tableName, column) {
    const formattedColumn = this.formatter.parameter(column);
    const formattedTable = this.formatter.parameter(
      this.formatter.wrap(prefixedTableName(this.schema, tableName))
    );
    const sql =
      `select object_id from sys.columns ` +
      `where name = ${formattedColumn} ` +
      `and object_id = object_id(${formattedTable})`;
    this.pushQuery({ sql, output: (resp) => resp.length > 0 });
  },
});

function prefixedTableName(prefix, table) {
  return prefix ? `${prefix}.${table}` : table;
}

module.exports = SchemaCompiler_MSSQL;