MVP模式MVP模式12-11 20:07

SQL语句收集

1、需要把某个字段中的括号及括号中的内容去掉

UPDATE 表 SET name=(case

when instr(name,'(') and instr(name,')') then concat(left(name,instr(name,'(')-1),substr(name, instr(name,')')+1))
when instr(name,'(') then  left(name, instr(name, '(')-1)
when instr(name, ')') then  substr(name, instr(name, ')')+1)

else
name
end) WHERE name like "%(%"

2.分页
表中主键必须为标识列,[ID] int IDENTITY (1,1)

1.分页方案一:(利用Not In和SELECT TOP分页)

语句形式:
SELECT TOP 页记录数量 *
FROM 表名
WHERE (ID NOT IN
(SELECT TOP (每页行数*(页数-1)) ID
FROM 表名
ORDER BY ID))
ORDER BY ID
//自己还可以加上一些查询条件

例:
select top 2 *
from Sys_Material_Type
where (MT_ID not in
(select top (2*(3-1)) MT_ID from Sys_Material_Type order by MT_ID))
order by MT_ID

2.分页方案二:(利用ID大于多少和SELECT TOP分页)

语句形式:
SELECT TOP 每页记录数量 *
FROM 表名
WHERE (ID >
(SELECT MAX(id)
FROM (SELECT TOP 每页行数*页数 id FROM 表
ORDER BY id) AS T)
)
ORDER BY ID

例:
SELECT TOP 2 *
FROM Sys_Material_Type
WHERE (MT_ID >
(SELECT MAX(MT_ID)
FROM (SELECT TOP (2*(3-1)) MT_ID
FROM Sys_Material_Type
ORDER BY MT_ID) AS T))
ORDER BY MT_ID

3.分页方案三:(利用SQL的游标存储过程分页)
create procedure SqlPager
@sqlstr nvarchar(4000), --查询字符串
@currentpage int, --第N页
@pagesize int --每页行数
as
set nocount on
declare @P1 int, --P1是游标的id
@rowcount int
exec sp_cursoropen @P1 output,@sqlstr,@scrollopt=1,@ccopt=1, @rowcount=@rowcount output
select ceiling(1.0@rowcount/@pagesize) as 总页数--,@rowcount as 总行数,@currentpage as 当前页
set @currentpage=(@currentpage-1)
@pagesize+1
exec sp_cursorfetch @P1,16,@currentpage,@pagesize
exec sp_cursorclose @P1
set nocount off

4.总结:
其它的方案:如果没有主键,可以用临时表,也可以用方案三做,但是效率会低。
建议优化的时候,加上主键和索引,查询效率会提高。

通过SQL 查询分析器,显示比较:我的结论是:
分页方案二:(利用ID大于多少和SELECT TOP分页)效率最高,需要拼接SQL语句
分页方案一:(利用Not In和SELECT TOP分页) 效率次之,需要拼接SQL语句
分页方案三:(利用SQL的游标存储过程分页) 效率最差,但是最为通用

5.删除重复数据
DELETE FROM t_extract_map
WHERE id in (
SELECT a.id from
( SELECT id from t_extract_map WHERE
(name,address) IN (
SELECT
name,
address
FROM
t_extract_map
GROUP BY
name,
address
HAVING
count() > 1
)
AND id NOT IN (
SELECT
min(id)
FROM
t_extract_map
GROUP BY
name,
address
HAVING
count(
) > 1
)
) as a
)

官场书屋二维码

小额赞赏

000
评论