text: DROP DATABASE IF EXISTS db1;
  
  CREATE DATABASE db1;
  USE db1;
  
  CREATE TABLE IF NOT EXISTS t1(a int, b varchar);
  SELECT * FROM system.tables WHERE database='db1';
  
  DROP TABLE t1;
  DROP TABLE IF EXISTS t1;
  DROP TABLE t1; -- {ErrorCode 25}
  
  DROP DATABASE db1;
  
  DROP DATABASE IF EXISTS db1;
  
  DROP DATABASE db1; -- {ErrorCode 3}
  