Mysql精华问答（五）| explain 进行Sql分析

{EXPLAIN | DESCRIBE | DESC}
    tbl_name [col_name | wild]


{EXPLAIN | DESCRIBE | DESC}
    [explain_type]
    {explainable_stmt | FOR CONNECTION connection_id}


explain_type: {
    EXTENDED
  | PARTITIONS
  | FORMAT = format_name
}


format_name: {
    TRADITIONAL
  | JSON
}


explainable_stmt: {
    SELECT statement
  | DELETE statement
  | INSERT statement
  | REPLACE statement
  | UPDATE statement
}

explain  select * from test1 t1 inner  join test1 t2 on t1.id=t2.id

explain  select * from test1 t1 where t1.id = (select  id  from  test1 t2 where  t2.id=2);

explain 
select t1.* from test1 t1
inner  join (select  max(id) mid  from test1 group  by  id) t2
on t1.id=t2.mid

explain select * from test1;

explain select * from test1 t1 where t1.id = (select id from  test1 t2 where  t2.id=2);

explain
select t1.* from test1 t1
inner join (select max(id) mid from test1 group by id) t2
on t1.id=t2.mid

explain
select * from test1
union
select* from test2

explain select * from test2 where id=1;

explain select * from test2 t1 inner join test2 t2 on t1.id=t2.id;

explain select * from test2 where code = '001';

explain select *  from test1 t1 inner join test1 t2 on t1.id=t2.id where t1.code='001';