SQL 语句解决实际问题

在项目开发过程中，遇到数据库的查询问题

一、查询某表字段的信息

select * from syscolumns
SELECT  object_id('TB_KYChildProject')
select * from syscolumns where id=object_id('TB_KYChildProject') and name='IsInheritAdd'

二、表字段添加说明

go
if exists(select 1 from sys.extended_properties p where
p.major_id = object_id('TB_KYChildProject')
and p.minor_id = (select c.column_id from sys.columns c where c.object_id = p.major_id and c.name = 'ChildProjectManageName')
)
begin
declare @CurrentUser sysname
select @CurrentUser = user_name()
execute sp_dropextendedproperty 'MS_Description',
'user', @CurrentUser, 'table', 'TB_KYChildProject', 'column', 'ChildProjectManageName'
end

select @CurrentUser = user_name()
execute sp_addextendedproperty 'MS_Description',
'子项目经理名称',
'user', @CurrentUser, 'table', 'TB_KYChildProject', 'column', 'ChildProjectManageName'
go

TB_KYChildProject是表名，ChildProjectManageName字段名，子项目经理名称是字段说明

三、将查询结果记录转换成 Insert SQL 语句

USE [BJSkyTwo_Dev]
GO
/****** Object:  StoredProcedure [dbo].[pCreateInsertScript]    Script Date: 10/31/2017 15:24:40 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
--@tablename  表名，@con 条件
--EXEC pCreateInsertScript @tablename = 'Find01_FindSetting',@con = 'Find01Find00ID =58'
ALTER  proc [dbo].[pCreateInsertScript] (@tablename varchar(256),@IsIncludeIdentityColumn BIT=0,@con varchar(MAX))
as
BEGIN
DECLARE @ID INT
SET @ID=object_id(@tablename)
declare @sql varchar(MAX)
declare @sqlValues varchar(MAX)
set @sql =' ('
set @sqlValues = 'values (''+'
select @sqlValues = @sqlValues + cols + ' + '','' + ' ,@sql = @sql + '[' + name + '],'
from
(select case
when xtype in (48,52,56,59,60,62,104,106,108,122,127)
then 'case when '+ name +' is null then ''NULL'' else ' + 'cast('+ name + ' as varchar)'+' end'

when xtype in (58,61)
then 'case when '+ name +' is null then ''NULL'' else '+''''''''' + ' + 'cast('+ name +' as varchar)'+ '+'''''''''+' end'
when xtype in (167)
then 'case when '+ name +' is null then ''NULL'' else '+''''''''' + ' + 'replace('+ name+','''''''','''''''''''')' + '+'''''''''+' end'
when xtype in (35)
then 'case when '+ name +' is null then ''NULL'' else '+''''''''' + ' + 'replace('+ 'cast('+ name + ' as varchar)'+','''''''','''''''''''')' + '+'''''''''+' end'
when xtype in (231)
then 'case when '+ name +' is null then ''NULL'' else '+'''N'''''' + ' + 'replace('+ name+','''''''','''''''''''')' + '+'''''''''+' end'
when xtype in (175)
then 'case when '+ name +' is null then ''NULL'' else '+''''''''' + ' + 'cast(replace('+ name+','''''''','''''''''''') as Char(' + cast(length as varchar)  + '))+'''''''''+' end'
when xtype in (239)
then 'case when '+ name +' is null then ''NULL'' else '+'''N'''''' + ' + 'cast(replace('+ name+','''''''','''''''''''') as Char(' + cast(length as varchar)  + '))+'''''''''+' end'
--when xtype in (36)
ELSE 'case when '+ name +' is null then ''NULL'' else '+'''N'''''' + ' + 'replace('+ name+','''''''','''''''''''')' + '+'''''''''+' end'

--else '''NULL'''
end as Cols,name
from syscolumns
where id = @ID
AND 1=(CASE WHEN @IsIncludeIdentityColumn=0 AND COLUMNPROPERTY(@ID,[name], 'IsIdentity') = 1 THEN 0 ELSE 1 END)
) T
set @sql ='select ''INSERT INTO ['+ @tablename + ']' + left(@sql,len(@sql)-1)+') ' + left(@sqlValues,len(@sqlValues)-4) + ')'' from '+@tablename+' where 1=1 and '+@con
print @sql
exec (@sql)
end

用法：

dbo.pCreateInsertScript @tablename = 'System_Menu', -- varchar(256)
@IsIncludeIdentityColumn = 0, -- bit
@con = 'MenuName = ''监理任务派单''' -- varchar(max)

存在的问题：

PRINT只能打印4000的Unicode string或8000的Non-unicode string，过长会导致字符串被截断

四、外键ID字符串拼接成对应名称字符串

转换成

方法一：

SELECT  a.userID ,
STUFF(( SELECT  ',' + System_Role.RoleName
FROM    System_Role
WHERE   CHARINDEX(','
+ CONVERT(VARCHAR(36), System_Role.RoleID)
+ ',', ',' + a.RoleIDs + ',') > 0
ORDER BY System_Role.RoleID
FOR
XML PATH('')
), 1, 1, '') AS RoleNames
FROM    System_Users a

方法二：

WITH    mt
AS ( SELECT   a.UserID ,
b.RoleID ,
b.RoleName
FROM     System_Users a ,
System_Role b
WHERE    ',' + a.RoleIDs + ',' LIKE '%,'
+ CONVERT(VARCHAR(36), b.RoleID) + ',%'
)
SELECT  UserID ,
STUFF(( SELECT  ',' + RoleName
FROM    mt a
WHERE   a.UserID = mt.UserID
FOR
XML PATH('')
), 1, 1, '') RoleNames
FROM    mt
GROUP BY UserID

五、统计某个类型占总数的比例

SELECT
SUM(CASE WHEN a.Sub_Project_Type =101 THEN 1
ELSE 0
END)*1.0  / COUNT(*) 类型比例
FROM    TB_KYSubProject a

效果：

六、用户所属的专业类型

思路一：

SELECT  a.* ,
STUFF(( SELECT  ',' + CONVERT(VARCHAR(100), b.RoleMajorType)
FROM    System_Role b
WHERE   CHARINDEX(',' + CONVERT(VARCHAR(36), b.RoleID) + ',',
',' + a.RoleIDs + ',') > 0
GROUP BY b.RoleMajorType
FOR
XML PATH('')
), 1, 1, '') AS RoleMajorType
FROM    System_Users a

效果：

思路二（不推荐）：

SELECT  a.* ,
STUFF(( SELECT  DISTINCT
( ',' + CONVERT(NVARCHAR(10), r.RoleMajorType) )
FROM    ( SELECT    a.UserID ,
b.RoleID
FROM      System_Users a
CROSS APPLY ( SELECT    CAST(col AS UNIQUEIDENTIFIER) RoleID
FROM      fn_split(RoleIDs,
',')
) b
) ru
LEFT JOIN dbo.System_Role r ON r.RoleID = ru.RoleID
WHERE   ru.UserID = a.UserID
FOR
XML PATH('')
), 1, 1, '') AS RoleMajorType
FROM    System_Users a
WHERE   1 = 1

效果：

七、截取字符串

1|216|368|截取成1|216|，1|2112|3683|21|截取成1|2112|

推荐

select LEFT('1|216|368|',CHARINDEX ('|', '1|216|368|' , CHARINDEX ('|', '1|216|368|')+1))

不推荐

select LEFT('1|216|368|',charindex('|',stuff('1|216|368|',charindex('|','1|216|368|'),1,',')))