高手帮忙解释下 这个搜索语句的作用
string str= "SELECT *,(SELECT name FROM businesssort where id = business.con_sort) as Con_sortname,(SELECT name FROM businesssort2 where id = business.con_xingzhi) as Con_sortname2,(SELECT name FROM businesssort3 where id = business.con_renshu) as Con_sortname3 FROM business order by id desc ";
其中括号里的什么意思啊 一共是有3个表
[解决办法]
括號裡面的就是三個子查詢。
改寫為如下方式更好些。
string str= "SELECT A.*, B.name as Con_sortname, C.name as Con_sortname2, D.name as Con_sortname3 FROM business A Inner Join businesssort B On A.con_sort = B.id Inner Join businesssort2 C On A.con_xingzhi = B.id Inner Join businesssort3 D On A.con_renshu = D.id order by A.id desc ";
[解决办法]
SELECT *,(SELECT name FROM businesssort where id = business.con_sort) as Con_sortname,(SELECT name FROM businesssort2 where id = business.con_xingzhi) as Con_sortname2,(SELECT name FROM businesssort3 where id = business.con_renshu) as Con_sortname3 FROM business order by id desc
提取表business中按照id倒序排列的所有记录，同时提取businesssort表中，id等于表business的con_sort的name值，别名为Con_sortname，其他的同理；
也可以建立视图的
