[转贴]精妙Sql 15句

精妙Sql语句
1． 判断a表中有而b表中没有的记录
select a.* from tbl1 a
left join tbl2 b
on a.key = b.key
where b.key is null
虽然使用in也可以实现，但是这种方法的效率更高一些
2． 新建一个与某个表相同结构的表
select * into b
from a where 1<>1
3．between的用法,between限制查询数据范围时包括了边界值,not between不包括
select * from table1 where time between time1 and time2
select a,b,c, from table1 where a not between 数值1 and 数值2
4. 说明：包括所有在 TableA 中但不在 TableB和TableC 中的行并消除所有重复行而派生出一个结果表
(select a from tableA ) except (select a from tableB) except (select a from tableC)
5. 初始化表，可以将自增长表的字增长字段置为1
TRUNCATE TABLE table1
6．多语言设置数据库或者表或者order by的排序规则
--修改用户数据库的排序规则
ater database dbname collate SQL_Latin1_General_CP1_CI_AS
--修改字段的排序规则
alter table a alter column c2 varchar(50) collate SQL_Latin1_General_CP1_CI_AS
--按姓氏笔画排序
select * from 表名 order by 列名 Collate Chinese_PRC_Stroke_ci_as
--按拼音首字母排序
select * from 表名 order by 列名 Collate Chinese_PRC_CS_AS_KS_WS
7．列出所有的用户数据表：
SELECT TOP 100 PERCENT o.name AS 表名
FROM dbo.syscolumns c INNER JOIN
dbo.sysobjects o ON o.id = c.id AND objectproperty(o.id, N'IsUserTable') = 1 AND
o.name <> 'dtproperties' LEFT OUTER JOIN
dbo.sysproperties m ON m.id = o.id AND m.smallid = c.colorder
WHERE (c.colid = 1)
ORDER BY o.name, c.colid

8．列出所有的用户数据表及其字段信息：
SELECT TOP 100 PERCENT c.colid AS 序号, o.name AS 表名, c.name AS 列名,
t.name AS 类型, c.length AS 长度, c.isnullable AS 允许空,
CAST(m.[value] AS Varchar(100)) AS 说明
FROM dbo.syscolumns c INNER JOIN
dbo.sysobjects o ON o.id = c.id AND objectproperty(o.id, N'IsUserTable') = 1 AND
o.name <> 'dtproperties' INNER JOIN
dbo.systypes t ON t.xusertype = c.xusertype LEFT OUTER JOIN
dbo.sysproperties m ON m.id = o.id AND m.smallid = c.colorder
ORDER BY o.name, c.colid
9．Left，right Join的另外一种简洁的写法
select * from a,b where a.id *= b.id --（*= 相当于 LEFT JOIN）
select * from a,b where a.id =* b.id --（=* 相当于 Right JOIN）
10．Update from 和 delete from
11．得到表中最小的未使用的ID号
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)
12．随机取得记录
SELECT TOP 10 * FROM T1 ORDER BY NEWID()

原文地址:
/article/4672433.html

13. 两张结构相同的表，使他们的数据同步
create table #A(id int, y vachar(10))
create table #B(id int, y varchar(10))

insert into #A
select 1, 'a1'
union
select 2, 'a2'
select * from #A

insert into #B
select 1, 'b1'
union
select 2, 'b2'
select * from #B

update #B set y=#A.y from #B,#A where #A.id=#B.id

select * from #B

drop table #A
drop table #B

14.对于一张表的一列,查找出不重复的记录
create table #A(x int,y varchar(10))
insert into #A
select 1, '张三'
union
select 2, '张三'
union
select 3, '李四'
select distinct y,count(y) [count] from #A group by y
drop table #A

15.将表A查询成下面的样子
表A

id x
1 abc
2 xyz
3 abc
4 abc

B
abc xyz
3 1

select * into #temp from( select
1 id, 'abc' x
union
select 2, 'xyz'
union
select 3, 'abc'
union
select 4, 'abc'
) A

select * from #temp
declare @sql varchar(8000)
set @sql = 'select '

select @sql = @sql + ltrim(str(f2)) + ' ' + f1 + ', ' from
(
select x f1, count(*) f2 from #temp group by x
) A

set @sql = substring(@sql, 1, len(@sql) - 1)

select @sql

exec( @sql )

drop table #temp