text: -- @testpoint: explain plan语句结合where条件的子查询减法运算
  -- @modify at: 2020-11-12
  --建表
  drop table if exists explain_t012;
  drop table if exists explain_t012_bak;
  create table explain_t012(a int, b int);
  create table explain_t012_bak(f1 int,f2 int);
  --使用explain plan语句，返回EXPLAIN SUCCESS
  explain plan for select t.a  from explain_t012 t where t.a = (select f1 from explain_t012_bak) - 1;
  --查询PLAN_TABLE表信息,statement_id字段为空
  select distinct object_name,statement_id from PLAN_TABLE where object_name = 'explain_t012' order by object_name;
  --清理PLAN_TABLE表信息
  delete from PLAN_TABLE;
  --删表
  drop table explain_t012;
  drop table explain_t012_bak;