数据库查询问题
select count(*) as a,SUM(id) as b ,b-a as c from table_name
怎么b-a说b字段不存在?如果要这样子写怎么写呢。
如果这样子写,那我的一些count很复杂的,不想重新写一次,有什么好办法?
select count(*) as a,SUM(id) as b ,SUM(id)-count(*) as c from table_name
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