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Exists CAsE

简单的用法比如: selelct user_id, user_name from tb_users where user_id in (select user_id from tb_course) 这个查询是查询在tb_course表中存在的user记录。 使用exists,写成 select user_id, user_name from tb_users where exists (sel...

SELECT (CASE WHEN MASTERJOB = '' THEN JOBNO ELSE MASTERJOB END)WO,JOBNO,CHILDJOB,CODE,BDESC,P_CODE, (SELECT TOP 1 BDESC FROM PRO WHERE CODE=RESVT.P_CODE)CBDESC,QTY,UNIT,LOC, (CASE WHEN exists(SELECT top 1 TAXUP FROM ANT B LEFT ...

UPDATE stuMarks1 SET writtenExam= case when exists(select stuno from stuMarks1 where writtenExam>80) then writtenExam-2 else writtenExam-5 end; 相当于如下两句 UPDATE stuMarks1 SET writtenExam=writtenExam+2 where exists (select ...

A resource exists with a different case 一个资源以不同的数据集存在。 case:A set of data to be used by a particular program. 由某种特定程序采用的一个数据集。

UPDATE stuMarks1 SET writtenExam= case when exists(select stuno from stuMarks1 where writtenExam>80) then writtenExam-2 else writtenExam-5 end; 相当于如下两句 UPDATE stuMarks1 SET writtenExam=writtenExam+2 where exists (select ...

EXISTS 是判断是否存在,和in类似,但效率要比in高 SELECT * FROM EMP (基础表) WHERE EMPNO > 0 AND EXISTS (SELECT ‘X' FROM DEPT WHERE DEPT.DEPTNO = EMP.DEPTNO AND LOC = ‘MELB') SELECT * FROM EMP (基础表) WHERE EMPNO > 0 AND DEPTNO IN...

UPDATE stuMarks1 SET writtenExam= case when exists(select stuno from stuMarks1 where writtenExam>80) then writtenExam-2 else writtenExam-5 end; 相当于如下两句 UPDATE stuMarks1 SET writtenExam=writtenExam+2 where exists (select ...

UPDATE stuMarks1 SET writtenExam= case when exists(select stuno from stuMarks1 where writtenExam>80) then writtenExam-2 else writtenExam-5 end; 相当于如下两句 UPDATE stuMarks1 SET writtenExam=writtenExam+2 where exists (select ...

exists : 强调的是是否返回结果集,不要求知道返回什么, 比如: select name from student where sex = 'm' and mark exists(select 1 from grade where ...) ,只要 exists引导的子句有结果集返回,那么exists这个条件就算成立了,大家注意返回的...

恩,对的,其实写法很多 1、 select id from a where id not in (select id_no from b) 2、 select id from a except select id_no from b

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