一个常见的问题是NOT IN可以处理多少个元素,而这在许多场合可能对性能影响较大。 基本用法 DELETE语句的基本语法如下: DELETEFROM表名WHERE条件; 1. 如果你想删除不在某些特定值中的记录,可以使用NOT IN子句。例如,假设我们有一个叫做employees的表,我们想删除不在特定部门的员工。SQL 查询如下: DELETEFROMemployees...
NOT IN条件用于在删除记录时排除某些特定值。例如,我们有一个名为students的表,其中包含学生的姓名和成绩。如果我们想删除成绩不及格的学生记录,可以使用NOT IN条件来排除成绩大于等于60分的学生。 以下是使用NOT IN条件的DELETE语句示例: DELETEFROMstudentsWHEREscoreNOTIN(SELECTscoreFROMstudentsWHEREscore>=60); 1....
delete from stu_score where id not in (select a.id from stu_score a,( select stu_id,course_id,max(score) as score from stu_score group by stu_id,course_id ) b where a.stu_id=b.stu_id and a.course_id=b.course_id and a.score=b.score) 处理结果: SQL>deletefromstu_scorewhere...
Mysql的sql语句,Delete 中包含 not in mysql delete not in 想要执行: DELETEFROMtb_tableAWHEREidIN(SELECTa.idFROMtb_tableA aWHEREa.idNOTIN(SELECTa_idFROMtb_tableB ) ); 是无法正确执行的。 解决方案:创建临时表,作为中间表;用完再删去。 CREATETABLEtmpASSELECTt.idFROM(SELECTa.idFROMtb_tableA aWH...
delete from A where ID in (1,2,3) and ID not in(select ID from B)或 delete from A where not exists (select ID from B where ID=A.ID) and ID in (1,2,3)
; ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 't1 where not exists (select * from test2 t2 where t1.testcol = t2.testcol)' at line 1 # try to delete without first ...
DELETE FROM CIDZ WHERE EXISTS (SELECT 1 FROM CIDZ A WHERE A.ID > CIDZ.ID AND A.地址 = CIDZ.地址)你运行一下试试。因为NOT IN是一个检索，要先运行IN里面的语句，这样相当于多了一个全表的检索操作，先把范围选出来，所以当你的表数据非常大的时候，速度会非常慢。可是EXISTS语句就不...
DELETE FROM comments_closure WHERE id IN(SELECT descendant FROM treepaths WHERE ancestor=4) 这样删的话只能删除 IN 条件中的第一条记录 也就是只能删除记录4 如果这样 DELETE FROM comments_closure WHERE id IN(4,5,6,7,8) 则可以全部删掉 . 不明白什么原因啊.请教各位.数据...
WHERE Specifies the conditions used to limit the number of rows that are deleted. If a WHERE clause is not supplied, DELETE removes all the rows from the table. There are two forms of delete operations based on what is specified in the WHERE clause: ...
delete from account where name in (select name from old_account); 我们explain执行计划走一波, 从explain结果可以发现:先全表扫描account,然后逐行执行子查询判断条件是否满足;显然,这个执行计划和我们预期不符合,因为并没有走索引。 但是如果换成把delete换成select,就会走索引。如下: ...