text: --- Case Type： Deallocate
  --- Case Name： 删除预备语句，带参数prepare
  
  --前置条件，创建表
  drop table if exists deallocate_test;
  create table deallocate_test(id int,name varchar(10));
  
  --创建insert预备语句
  prepare insert_sql(int,varchar(10)) as insert into deallocate_test values($1,$2);
  
  --执行预备语句
  execute insert_sql(2,'b');
  
  --删除预备语句，带参数prepare
  deallocate prepare insert_sql;
  
  --再次执行预备语句，语句已不存在
  execute insert_sql(1,'a');
  
  --清理环境
  drop table deallocate_test;
  
  