mysql语句技巧——拼表、生成序列

生成序列(mysql没有函数生成序列，可以用下面语句生成序列)

select 1 as loli union select 2 as loli union select 3 as loli

把序列当成表搜索

select * from (select 1 as loli union select 2 as loli union select 3 as loli) as b;

拼表

select * from ((select 1 as num1) as a,(select 2 as num2) as b);

拿mysql数据库做拼表测试

select * from ((select user from user) as a,(select Db from db) b);

select * from ((select user from user) as a left join (select user,Db from db) b on a.user=b.user and b.db = 'mysql');

所有表必须有别名才能拼接

待补充