精妙的SQL语句

下面是我搜集的一些精妙的SQL语句



说明：复制表(只复制结构,源表名：a 新表名：b)

Sql代码
1.select * into b from a where 1<>1 
select * into b from a where 1<>1

说明：拷贝表(拷贝数据,源表名：a 目标表名：b)

Sql代码
1.insert into b(a, b, c) select d,e,f from b; 
insert into b(a, b, c) select d,e,f from b;

说明：显示文章、提交人和最后回复时间

Java代码
1.select a.title,a.username,b.adddate   
2.from table a,(  
3.select max(adddate) adddate   
4.from table   
5.where table.title=a.title  
6.) b 
select a.title,a.username,b.adddate
from table a,(
select max(adddate) adddate
from table
where table.title=a.title
) b
 

说明：外连接查询(表名1：a 表名2：b)

Sql代码
1.select a.a, a.b, a.c, b.c, b.d, b.f from a LEFT OUT JOIN b ON a.a = b.c 
select a.a, a.b, a.c, b.c, b.d, b.f from a LEFT OUT JOIN b ON a.a = b.c

说明：日程安排提前五分钟提醒

Sql代码
1.select * from 日程安排 where datediff('minute',f开始时间,getdate())>5 
select * from 日程安排 where datediff('minute',f开始时间,getdate())>5

说明：两张关联表，删除主表中已经在副表中没有的信息

Sql代码
1.delete from info where not exists ( select * from infobz where info.infid=infobz.infid ) 
delete from info where not exists ( select * from infobz where info.infid=infobz.infid )

说明：四表联查问题：

Sql代码
1.select * from a left inner join b on a.a=b.b right inner join c on a.a=c.c  inner join d on a.a=d.d where ..... 
select * from a left inner join b on a.a=b.b right inner join c on a.a=c.c  inner join d on a.a=d.d where .....


说明：得到表中最小的未使用的ID号

Sql代码
1.SELECT (CASE WHEN EXISTS(SELECT * FROM Handle b WHERE b.HandleID = 1) THEN MIN(HandleID) + 1 ELSE 1 END) as HandleID  
2.FROM  Handle  
3.WHERE NOT HandleID IN (SELECT a.HandleID - 1 FROM Handle a)  
4.COALESCE 
SELECT (CASE WHEN EXISTS(SELECT * FROM Handle b WHERE b.HandleID = 1) THEN MIN(HandleID) + 1 ELSE 1 END) as HandleID
FROM  Handle
WHERE NOT HandleID IN (SELECT a.HandleID - 1 FROM Handle a)
COALESCE


返回其参数中第一个非空表达式。



语法
COALESCE ( expression [ ,...n ] )