MySQL子查询

1、IN 关键字 

SECLET * FROM SCORES WHERE gno IN

（SECLET gno FROM games WHERE gtype=’棋牌‘）

注意：子查询一般不写成SECLET *FROM....

2、EXISTS关键字

SECLET * FROM SCORES

WHERE EXISTS

(SECLET * FROM USERS WHERE USER_NAME='孙悟空’)