请问怎么从A表查出B表？

sqlserver 中可以使用pivot实现 mysql 不支持该语法 

where B.?=?

你这个是纵表转成横表。。。。什么查出。。

mysql的话可以这样写，性能差勿喷： select t1.name,t1.score as 语文,t2.score as 数学,t3.score as 英语 from (select A.name,A.score from A where A.subject = '语文') as t1,  (select A.name,A.score from A where A.subject = '数学') as t2, (select A.name,A.score from A where A.subject = '英语') as t3 where t1.name = t2.name and t1.name = t3.name;

行转列 和列转行都可以实现，找个博客看下

select name, max(case subject when '语文' then score else 0 end) 语文, max(case subject when '数学' then score else 0 end) 数学, max(case subject when '英语' then score else 0 end) 英语 from a group by name;  mysql 列传行，我已经找到答案了，谢谢大家。