MSSQL 临时表和公用表使用案例

1、临时表：

1.1）实例1

if(OBJECT_ID('tempdb..#a') IS NOT NULL) drop table #a; if(OBJECT_ID('tempdb..#b') IS NOT NULL) drop table #b; SELECT name into #a from syscolumns a with(nolock) where id=OBJECT_ID('NewsLetterSystem_Subscriber'); SELECT name into #b from syscolumns b where id=OBJECT_ID('tmpContact_130828005535769_5243_f0b7'); select * from #a,#b where #a.name=#b.name;

1.2） 实例2

if(OBJECT_ID('tempdb..#a') IS NOT NULL) drop table #a; select * into #a from Categories; select * from #a;

 

2、公用表：

2.1）实例1

with cr as ( select CountryRegionCode from person.CountryRegion where Name like 'C%' ) select * from person.StateProvince where CountryRegionCode in (select * from cr) --其中cr是一个公用表表达式，该表达式在使用上与表变量类似

2.2） CTE后面必须直接跟使用CTE的SQL语句（如select、insert、update等），否则，CTE将失效。如下面的SQL语句将无法正常使用CTE：

with cr as ( select CountryRegionCode from person.CountryRegion where Name like 'C%' ) select * from person.CountryRegion -- 应将这条SQL语句去掉 -- 使用CTE的SQL语句应紧跟在相关的CTE后面 -- select * from person.StateProvince where CountryRegionCode in (select * from cr)

2.3）CTE后面也可以跟其他的CTE，但只能使用一个with，多个CTE中间用逗号（,）分隔，如下面的SQL语句所示：

with cte1 as ( select * from table1 where name like 'abc%' ), cte2 as ( select * from table2 where id > 20 ), cte3 as ( select * from table3 where price < 100 ) select a.* from cte1 a, cte2 b, cte3 c where a.id = b.id and a.id = c.id

2.4）实例4

with ta as ( SELECT name from syscolumns a with(nolock) where id=OBJECT_ID('NewsLetterSystem_Subscriber') ), tb as ( SELECT name from syscolumns b where id=OBJECT_ID('tmpContact_130828005535769_5243_f0b7') ) select * from ta,tb where ta.name=tb.name

 

 

ps:将一个库中数据插到另一个库中：

语句：

insert into b.dbo.b select * from a.dbo.a

实例1：

insert into dbname1.dbo.tabname1 select * from dbname2.dbo.tabname2

 

判断临时表是否存在sql:

if(OBJECT_ID('tempdb..#c') is not null) drop table #cif(OBJECT_ID('tempdb..#e') is not null) drop table #e if(OBJECT_ID('tempdb..#newc') is not null) drop table #newc

 

转载于:https://www.cnblogs.com/zoro-zero/p/6879982.html

相关资源：mysql8 公用表表达式CTE的使用方法实例分析