同时查询多张表中的数据个数

select my1.a,my2.b,my3.c from (select count(*) as a from tbl_a) as my1 , (select count(*) as b from tbl_b) as my2 , (select count(*) as c from tbl_c) as my3;

同时查询两张表

select * from (select * from tbl_a) as a,(select * from tbl_b) as b;