笔记 : SQL Cookbook

连接字符串: concat

条件逻辑： select col_a, case when col_b<100 then 'small' else 'big' end as state from sometable

按某个字段的最后两个字符升序：select col_a,col_b from sometable order by substring(col_b, length(col_b)-2)

重叠结果输出：[SELECT SQL A] union all [SELECT SQL B]

union all不删重复项；union删重复项；除非必要，否则不要用union、distinct

从一个表中取数据导入另一个表：insert into table1(col_a, col_b) select (col_aa, col_bb) from table2 where colcc='somevalue'

出现三次以上部门：select col_a from sometable group by col_a having count(*)>=3

列出索引：show index from emp

正则：select data from sometable where data regexp '[^0-9]' = 0

将同一部门的人名合在一行显示：select dept, group_concat(name order by id, ',') from emp group by dept

滚动结果集，每页五行(limit 5)，显示第2页(offset 5)：select col_a from sometable order by col_a limit 5 offset 5