目录
- 从表中去除重复行
- 逗号分隔字符串转数据表行
- 跨DB/Server执行SP[分布式事务]
- 在OpenQuery中执行带参数的SQL语句
从表中去除重复行数据
1. 如果有ID字段,就是具有唯一性的字段
-- group by 子句后跟的字段就是你用来判断重复的条件,如只有col1,那么只要col1字段内容相同即表示记录相同。
delete table tableName
where id not in ( select max(id) from table group by col1,col2,col3... )
2. 如果是判断所有字段也可以这样 ,【对于表中的指定的字段的进行检查是否相同】
select * into #temp from tablename group by id1,id2,....
delete tablename
insert into table select * from #temp
drop table #temp
3. 首先去重复,再获取N*1条数据插入到临时表中,【对于表中的所有字段的进行检查是否相同】,再将原表的数据删除,然后将临时表的数据插入到原表,最后删除临时表。
select distinct * into #temp from tablename
delete tablename
go
insert tablename select * from #temp
go
drop table #temp
4. 没有ID的情况
select identity(int,1,1) as id,* into #temp from tabel
delect # where id not in (
select max(id) from # group by col1,col2,col3...)
delect table
inset into table(...)
select ..... from #temp
5. col1+','+col2+','...col5 联合主键
select * from table where col1+','+col2+','...col5 in (
select max(col1+','+col2+','...col5) from table
where having count(*)>1
group by col1,col2,col3,col4
)
-- group by 子句后跟的字段就是你用来判断重复的条件,如只有col1,那么只要col1字段内容相同即表示记录相同。
6. 使用自增列
select identity(int,1,1) as id,* into #temp from tabel
select * from #temp where id in (
select max(id) from #emp where having count(*)>1 group by col1,col2,col3...)
逗号分隔字符串转数据表行
1. 使用CHARINDEX和SUBSTRING函数
CREATE FUNCTION dbo.splitstring
(
@stringToSplit VARCHAR(MAX)
)
RETURNS @returnList TABLE ( [Name] [nvarchar](500) )
AS
BEGIN
DECLARE @name NVARCHAR(255)
DECLARE @pos INT
WHILE CHARINDEX(',', @stringToSplit) > 0
BEGIN
SELECT @pos = CHARINDEX(',', @stringToSplit)
SELECT @name = SUBSTRING(@stringToSplit, 1, @pos - 1)
INSERT INTO @returnList
SELECT @name
SELECT @stringToSplit = SUBSTRING(@stringToSplit, @pos + 1,
LEN(@stringToSplit) - @pos)
END
INSERT INTO @returnList
SELECT @stringToSplit
RETURN
END
2. 使用XML-Method[SQL Server 2005+]
CREATE FUNCTION [dbo].[ufnGetSplitValues]
(
@StringValues NVARCHAR(4000),
@Delimiter CHAR(1)
)
RETURNS TABLE
AS
RETURN
(
SELECT LTRIM(RTRIM(Split.a.value('.', 'NVARCHAR(100)'))) 'Value'
FROM
(
SELECT CAST ('' + REPLACE(@StringValues, @Delimiter, ' ') + ' ' AS XML) AS Data
) AS A
CROSS APPLY Data.nodes ('/M') AS Split(a)
)
GO
3. STRING_SPLIT()函数[SQL Server 2016 +]
SELECT * FROM STRING_SPLIT('a,b,cd', ',');
/* result:
value
--------
a
b
cd
*/
4. 参考资料
- https://sqlperformance.com/2016/03/t-sql-queries/string-split
- http://stackoverflow.com/questions/5493510/turning-a-comma-separated-string-into-individual-rows
跨DB/Server执行SP[分布式事务]
USE Database1
GO
-- 如果不加SET FMTONLY OFF,在执行时可能会出现分布式事务异常
SELECT name, age, sex INTO #Persons FROM OPENQUERY(LinkedServer,
'SET FMTONLY OFF EXEC [database2].[dbo].uspGetPersonList')
在OpenQuery中执行带参数的SQL语句
DECLARE @Sql VARCHAR(1000)
DECLARE @organizationID VARCHAR(10)
SELECT @organizationID = (SELECT ORGANIZATION_ID FROM MYORGS WHERE ORGANIZATION_NAME = 'MMT')
SET @Sql = 'SELECT * from tableName where organization_id ='+@organizationID
SET @Sql = 'SELECT * FROM OPENQUERY(LinkedServerName, ''' + REPLACE(@Sql, '''', '''''') + ''')'
EXEC(@Sql)