sql行列转换
业务里偶尔会遇到sql行列转换的问题，更多的是面试的时候会遇到...zzz
如下，1.把a表的结果集用sql显示成b表的形式 2.b=>a

select * from table a;+------+------+---------+| name | math | english |+------+------+---------+| anna |   80 |      97 || mike |   76 |      86 |+------+------+---------+select * from table b;+------+---------+-------+| name | subject | score |+------+---------+-------+| anna | shuxue  |    80 || anna | yingyu  |    97 || mike | shuxue  |    76 || mike | yingyu  |    86 |+------+---------+-------+--1.a=>b转换 select name,'shuxue' as subject,math as score from a union all select name,'yingyu' as subject ,english as score from a order by name;--2.b=>a转换 select name,max(math) as math,max(english)as english  from(   select name,case when subject='shuxue' then score end as math,   case when subject='yingyu' then score end as english   from b ) t  group by name;

sql cookbook里有好多例子，一本实用的工具书。