为什么sql里面not in后面的子查询如果有记录为NULL的,主查询就查不到记录???原因很简单: SELECT * FROM dbo.TableA AS a WHERE a.id NOT IN ( 2, NULL ) –等同于: SELECT * FROM Table_A AS a WHERE a.id <> 2 AND a.ID <> NULL 由于NULL值不能参与比较运算符,导致条件不成立,查询不出来数据. 转载:https://blog.csdn.net/coder_o…
原文:在论坛中出现的比较难的sql问题:4(row_number函数+子查询 分组连续编号问题) 所以,觉得有必要记录下来,这样以后再次碰到这类问题,也能从中获取解答的思路. 求一查询语句 http://bbs.csdn.net/topics/390633004 CREATE #temp (cName CHAR(1),re int) INSERT #temp SELECT 'A',1 UNION ALL SELECT 'A',2 UNION ALL SELECT 'B',3 UNION ALL…
前言 本节我们来综合比较NOT IN VS NOT EXISTS VS LEFT JOIN...IS NULL的性能,简短的内容,深入的理解,Always to review the basics. NOT IN.NOT EXISTS.LEFT JOIN...IS NULL性能分析 我们首先创建测试表 USE TSQL2012 GO CREATE SCHEMA [compare] CREATE TABLE [compare].t_left ( id INT NOT NULL PRIMARY KE…
1.查询数据表的属性(名称.说明.是否主键.数据类型.是否自增) SELECT t1.name columnName,case when t4.id is null then 'false' else 'true' end as pkColumn, case when COLUMNPROPERTY( t1.id,t1.name,'IsIdentity') = 1 then 'true' else 'false' end as autoAdd ,t5.name jdbcType ,cast(isn…
1.连表子查询获取值 select bas.name,bas.id_card_num,bas.mobil_no,gender,bas.birthday,bas.height,bas.weight,province.value as province,city.value as city,area.value as area,profession.value as profession from xy_user_baseinf bas LEFT JOIN (select usr_no,`value…
待优化语句如下 select a.code as code, a.m_code as m_code,a.stktype as f_stype,a.e_year as e_year, b.sname as sname,a.c_date as c_date,to_char(sysdate,'YYYYMMDD') as createtime, to_char(sysdate,'YYYYMMDD') as updatetime, (,'YYYYMMDD') and a.c_date and t.e_ye…
1.所有的子节点查询到树结构中所有父节点 RETURNS @Tree Table(PID )) as begin --DECLARE @ID VARCHAR() --SET @ID = ' ;with rolDepList as ( ) union all select a.PID,a.FID,a.Name from tbDepList a join rolDepList b on a.pid=b.fid ) Insert @Tree select distinct(PID),FID,Name…
--1. 使用IN关键字 --例1 查询系别人数不足5人的系别中学生的学号.姓名和系别 --系别人数不足5人的系别 ==>选择条件 select Sdept from Student Group by Sdept --显示这些系别的学生信息 Select sno, sname, sdept From Student WHERE sdept IN ( select Sdept from Student Group by Sdept ) --2. 使用EXISTS关键字 --例2 如果“MA"…
