学习sql有什么诀窍没有啊

没有捷径,熟悉SQL语法,一些常用的关键字,能很牛的写出查询语句就很不得了啦,自己多动手 多练一练.

哈哈 把下面这个语句读懂先

SELECT m.AD_Menu_ID, m.Name,m.Description,m.IsSummary,m.Action, m.AD_Window_ID, m.AD_Process_ID, m.AD_Form_ID, m.AD_Workflow_ID, m.AD_Task_ID, m.AD_Workbench_ID FROM AD_Menu m WHERE m.IsActive='Y' AND (m.AD_Window_ID IS NULL OR EXISTS (SELECT * FROM AD_Window w WHERE m.AD_Window_ID=w.AD_Window_ID AND w.IsBetaFunctionality='N')) AND (m.AD_Process_ID IS NULL OR EXISTS (SELECT * FROM AD_Process p WHERE m.AD_Process_ID=p.AD_Process_ID AND p.IsBetaFunctionality='N')) AND (m.AD_Form_ID IS NULL OR EXISTS (SELECT * FROM AD_Form f WHERE m.AD_Form_ID=f.AD_Form_ID AND f.IsBetaFunctionality='N')) AND (m.AD_Form_ID IS NULL OR EXISTS (SELECT * FROM AD_Form f WHERE m.AD_Form_ID=f.AD_Form_ID AND f.Classname IS NOT NULL)) AND m.AD_Client_ID=0 AND m.AD_Org_ID=0 ;

我也想知道，呵呵

应该没有什么诀窍，多动手吧!

背

3楼写那么多， 就是复合查询 ，怎么没见join