Sql server SQL:仅选择具有空值的列
如何选择表中仅包含所有行的空值的所有列?我正在使用MS SQL Server 2005。我试图找出表中没有使用的列,以便删除它们。您可能需要澄清一下。你到底想完成什么?如果您真的想找出只包含空值的列名,那么您必须遍历scheama并基于此执行动态查询Sql server SQL:仅选择具有空值的列,sql-server,Sql Server,如何选择表中仅包含所有行的空值的所有列?我正在使用MS SQL Server 2005。我试图找出表中没有使用的列,以便删除它们。您可能需要澄清一下。你到底想完成什么?如果您真的想找出只包含空值的列名,那么您必须遍历scheama并基于此执行动态查询 SELECT cols FROM table WHERE cols IS NULL 我不知道您使用的是哪种DBMS,所以我将在这里放一些伪代码 for each col begin @cmd = 'if not exists (select
SELECT cols
FROM table
WHERE cols IS NULL
我不知道您使用的是哪种DBMS,所以我将在这里放一些伪代码
for each col
begin
@cmd = 'if not exists (select * from tablename where ' + col + ' is not null begin print ' + col + ' end'
exec(@cmd)
end
或者您只是想看看一列是否只有空值,因此可能未使用 进一步澄清这个问题可能会有所帮助 编辑: 好啊这里有一些非常粗略的代码让你去
SET NOCOUNT ON
DECLARE @TableName Varchar(100)
SET @TableName='YourTableName'
CREATE TABLE #NullColumns (ColumnName Varchar(100), OnlyNulls BIT)
INSERT INTO #NullColumns (ColumnName, OnlyNulls) SELECT c.name, 0 FROM syscolumns c INNER JOIN sysobjects o ON c.id = o.id AND o.name = @TableName AND o.xtype = 'U'
DECLARE @DynamicSQL AS Nvarchar(2000)
DECLARE @ColumnName Varchar(100)
DECLARE @RC INT
SELECT TOP 1 @ColumnName = ColumnName FROM #NullColumns WHERE OnlyNulls=0
WHILE @@ROWCOUNT > 0
BEGIN
SET @RC=0
SET @DynamicSQL = 'SELECT TOP 1 1 As HasNonNulls FROM ' + @TableName + ' (nolock) WHERE ''' + @ColumnName + ''' IS NOT NULL'
EXEC sp_executesql @DynamicSQL
set @RC=@@rowcount
IF @RC=1
BEGIN
SET @DynamicSQL = 'UPDATE #NullColumns SET OnlyNulls=1 WHERE ColumnName=''' + @ColumnName + ''''
EXEC sp_executesql @DynamicSQL
END
ELSE
BEGIN
SET @DynamicSQL = 'DELETE FROM #NullColumns WHERE ColumnName=''' + @ColumnName+ ''''
EXEC sp_executesql @DynamicSQL
END
SELECT TOP 1 @ColumnName = ColumnName FROM #NullColumns WHERE OnlyNulls=0
END
SELECT * FROM #NullColumns
DROP TABLE #NullColumns
SET NOCOUNT OFF
是的,有更简单的方法,但我现在有个会议要开。祝你好运 您必须在列集合上循环并检查每个列。您应该能够使用descripe table命令获得所有列的列表 伪代码: 我知道这似乎有点违反直觉,但SQL不提供选择列的本机方法,只提供行。您可以:
select
count(<columnName>)
from
<tableName>
如果计数返回0,则表示该列中的所有行都为NULL,或者表中根本没有行
可以改为
select
case(count(<columnName>)) when 0 then 'Nulls Only' else 'Some Values' end
from
<tableName>
如果要实现自动化,可以使用系统表来迭代您感兴趣的表中的列名我还建议搜索所有字段都具有相同的值,而不仅仅是空值 也就是说,对每个表中的每一列执行以下查询:
SELECT COUNT(DISTINCT field) FROM tableName
然后将注意力集中在那些结果返回1的列上。这将为您提供一个Person表中所有只有空值的列的列表。您将以多个结果集的形式获得结果,这些结果集要么为空,要么包含单个列的名称。您需要在两个位置替换人员,才能使用另一个表
DECLARE crs CURSOR LOCAL FAST_FORWARD FOR SELECT name FROM syscolumns WHERE id=OBJECT_ID('Person')
OPEN crs
DECLARE @name sysname
FETCH NEXT FROM crs INTO @name
WHILE @@FETCH_STATUS = 0
BEGIN
EXEC('SELECT ''' + @name + ''' WHERE NOT EXISTS (SELECT * FROM Person WHERE ' + @name + ' IS NOT NULL)')
FETCH NEXT FROM crs INTO @name
END
CLOSE crs
DEALLOCATE crs
以下是sql 2005或更高版本:用您的表名替换ADDR_地址
declare @col varchar(255), @cmd varchar(max)
DECLARE getinfo cursor for
SELECT c.name FROM sys.tables t JOIN sys.columns c ON t.Object_ID = c.Object_ID
WHERE t.Name = 'ADDR_Address'
OPEN getinfo
FETCH NEXT FROM getinfo into @col
WHILE @@FETCH_STATUS = 0
BEGIN
SELECT @cmd = 'IF NOT EXISTS (SELECT top 1 * FROM ADDR_Address WHERE [' + @col + '] IS NOT NULL) BEGIN print ''' + @col + ''' end'
EXEC(@cmd)
FETCH NEXT FROM getinfo into @col
END
CLOSE getinfo
DEALLOCATE getinfo
如果您需要列出所有列值为NULL的所有行,那么我将使用COLLATE函数。这将获取值列表并返回第一个非空值。如果将所有列名添加到列表中,则use为NULL,则应获取仅包含NULL的所有行
SELECT * FROM MyTable WHERE COLLATE(Col1, Col2, Col3, Col4......) IS NULL
您不应该有任何表的所有列都为null,因为这意味着您没有不允许为null的主键。没有主键是需要避免的;这打破了第一个正常形式。试试这个-
DECLARE @table VARCHAR(100) = 'dbo.table'
DECLARE @sql NVARCHAR(MAX) = ''
SELECT @sql = @sql + 'IF NOT EXISTS(SELECT 1 FROM ' + @table + ' WHERE ' + c.name + ' IS NOT NULL) PRINT ''' + c.name + ''''
FROM sys.objects o
JOIN sys.columns c ON o.[object_id] = c.[object_id]
WHERE o.[type] = 'U'
AND o.[object_id] = OBJECT_ID(@table)
AND c.is_nullable = 1
EXEC(@sql)
这是Bryan 2008年及以后查询的更新版本。它使用INFORMATION_SCHEMA.COLUMNS,为表模式和表名添加变量。列数据类型已添加到输出中。包含列数据类型有助于查找特定数据类型的列。我没有添加列宽或其他内容 对于输出错误。。。使用NOWAIT时,文本将立即显示,而不是像PRINT一样在末尾显示大部分内容
SET NOCOUNT ON;
DECLARE
@ColumnName sysname
,@DataType nvarchar(128)
,@cmd nvarchar(max)
,@TableSchema nvarchar(128) = 'dbo'
,@TableName sysname = 'TableName';
DECLARE getinfo CURSOR FOR
SELECT
c.COLUMN_NAME
,c.DATA_TYPE
FROM
INFORMATION_SCHEMA.COLUMNS AS c
WHERE
c.TABLE_SCHEMA = @TableSchema
AND c.TABLE_NAME = @TableName;
OPEN getinfo;
FETCH NEXT FROM getinfo INTO @ColumnName, @DataType;
WHILE @@FETCH_STATUS = 0
BEGIN
SET @cmd = N'IF NOT EXISTS (SELECT * FROM ' + @TableSchema + N'.' + @TableName + N' WHERE [' + @ColumnName + N'] IS NOT NULL) RAISERROR(''' + @ColumnName + N' (' + @DataType + N')'', 0, 0) WITH NOWAIT;';
EXECUTE (@cmd);
FETCH NEXT FROM getinfo INTO @ColumnName, @DataType;
END;
CLOSE getinfo;
DEALLOCATE getinfo;
“user2466387”版本的更新版本,带有额外的小测试,可以提高性能,因为测试不可为null的列是无用的:
AND IS_NULLABLE = 'YES'
完整代码:
SET NOCOUNT ON;
DECLARE
@ColumnName sysname
,@DataType nvarchar(128)
,@cmd nvarchar(max)
,@TableSchema nvarchar(128) = 'dbo'
,@TableName sysname = 'TableName';
DECLARE getinfo CURSOR FOR
SELECT
c.COLUMN_NAME
,c.DATA_TYPE
FROM
INFORMATION_SCHEMA.COLUMNS AS c
WHERE
c.TABLE_SCHEMA = @TableSchema
AND c.TABLE_NAME = @TableName
AND IS_NULLABLE = 'YES';
OPEN getinfo;
FETCH NEXT FROM getinfo INTO @ColumnName, @DataType;
WHILE @@FETCH_STATUS = 0
BEGIN
SET @cmd = N'IF NOT EXISTS (SELECT * FROM ' + @TableSchema + N'.' + @TableName + N' WHERE [' + @ColumnName + N'] IS NOT NULL) RAISERROR(''' + @ColumnName + N' (' + @DataType + N')'', 0, 0) WITH NOWAIT;';
EXECUTE (@cmd);
FETCH NEXT FROM getinfo INTO @ColumnName, @DataType;
END;
CLOSE getinfo;
DEALLOCATE getinfo;
实际上不确定2005年,但2008年吃了它:
USE [DATABASE_NAME] -- !
GO
DECLARE @SQL NVARCHAR(MAX)
DECLARE @TableName VARCHAR(255)
SET @TableName = 'TABLE_NAME' -- !
SELECT @SQL =
(
SELECT
CHAR(10)
+'DELETE FROM ['+t1.TABLE_CATALOG+'].['+t1.TABLE_SCHEMA+'].['+t1.TABLE_NAME+'] WHERE '
+(
SELECT
CASE t2.ORDINAL_POSITION
WHEN (SELECT MIN(t3.ORDINAL_POSITION) FROM INFORMATION_SCHEMA.COLUMNS t3 WHERE t3.TABLE_NAME=t2.TABLE_NAME) THEN ''
ELSE 'AND '
END
+'['+COLUMN_NAME+'] IS NULL' AS 'data()'
FROM INFORMATION_SCHEMA.COLUMNS t2 WHERE t2.TABLE_NAME=t1.TABLE_NAME FOR XML PATH('')
) AS 'data()'
FROM INFORMATION_SCHEMA.TABLES t1 WHERE t1.TABLE_NAME = @TableName FOR XML PATH('')
)
SELECT @SQL -- EXEC(@SQL)
在这里,我为任何类型的SQL表创建了一个脚本。请复制此存储过程并在您的环境中创建它,然后在表中运行此存储过程
exec [dbo].[SP_RemoveNullValues] 'Your_Table_Name'
存储过程
GO
/****** Object: StoredProcedure [dbo].[SP_RemoveNullValues] Script Date: 09/09/2019 11:26:53 AM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- akila liyanaarachchi
Create procedure [dbo].[SP_RemoveNullValues](@PTableName Varchar(50) ) as
begin
DECLARE Cussor CURSOR FOR
SELECT COLUMN_NAME,TABLE_NAME,DATA_TYPE
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = @PTableName
OPEN Cussor;
Declare @ColumnName Varchar(50)
Declare @TableName Varchar(50)
Declare @DataType Varchar(50)
Declare @Flage int
FETCH NEXT FROM Cussor INTO @ColumnName,@TableName,@DataType
WHILE @@FETCH_STATUS = 0
BEGIN
set @Flage=0
If(@DataType in('bigint','numeric','bit','smallint','decimal','smallmoney','int','tinyint','money','float','real'))
begin
set @Flage=1
end
If(@DataType in('date','atetimeoffset','datetime2','smalldatetime','datetime','time'))
begin
set @Flage=2
end
If(@DataType in('char','varchar','text','nchar','nvarchar','ntext'))
begin
set @Flage=3
end
If(@DataType in('binary','varbinary'))
begin
set @Flage=4
end
DECLARE @SQL VARCHAR(MAX)
if (@Flage in(1,4))
begin
SET @SQL =' update ['+@TableName+'] set ['+@ColumnName+']=0 where ['+@ColumnName+'] is null'
end
if (@Flage =3)
begin
SET @SQL =' update ['+@TableName+'] set ['+@ColumnName+'] = '''' where ['+@ColumnName+'] is null '
end
if (@Flage =2)
begin
SET @SQL =' update ['+@TableName+'] set ['+@ColumnName+'] ='+'''1901-01-01 00:00:00.000'''+' where ['+@ColumnName+'] is null '
end
EXEC(@SQL)
FETCH NEXT FROM Cussor INTO @ColumnName,@TableName,@DataType
END
CLOSE Cussor
DEALLOCATE Cussor
END
根据我对这个问题的理解,他想知道只有空值的列的列表。我正在尝试查找表中每一行中包含空值的所有列。这应该可以工作,但可以简化。。。而不是计数*只要做一个前1,并设置一个变量,表示你得到了一个命中。。。不需要知道有多少不是空的,只要至少有一个不是…MSSQL。。。线索在标签上;这并不能回答问题,但我想你的意思是,而不是整理。那么,我该如何做相反的事情,即只选择非空值的列?将代码中的IS NOT NULL更改为IS NULL?@Steam从WHILE内的查询中删除NOT,您将得到一个列列表,其中至少有一条带值的记录。这只是说,如果没有所有列都为NULL,则该命令在没有其他输出的情况下成功运行?嗨,Charles..此代码不适用于临时表。从临时表中获取值是否需要任何更改?虽然此代码可能会回答此问题,但提供有关如何和/或为什么解决此问题的附加上下文将提高答案的长期值。请阅读这篇文章,提供高质量的答案。在一个非常大的表格上,可以扫描数百万或数十亿条记录。如果使用EXISTS,则至少可以在会使列作为感兴趣的列无效的条件下短路。该问题要求MS SQL Serv的解决方案
er 2005这段代码对我来说非常有效!!!提示是将结果格式设置为文本,以便您可以快速复制结果并获得所需内容。谢谢你,莫比!这个对我有用
exec [dbo].[SP_RemoveNullValues] 'Your_Table_Name'
GO
/****** Object: StoredProcedure [dbo].[SP_RemoveNullValues] Script Date: 09/09/2019 11:26:53 AM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- akila liyanaarachchi
Create procedure [dbo].[SP_RemoveNullValues](@PTableName Varchar(50) ) as
begin
DECLARE Cussor CURSOR FOR
SELECT COLUMN_NAME,TABLE_NAME,DATA_TYPE
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = @PTableName
OPEN Cussor;
Declare @ColumnName Varchar(50)
Declare @TableName Varchar(50)
Declare @DataType Varchar(50)
Declare @Flage int
FETCH NEXT FROM Cussor INTO @ColumnName,@TableName,@DataType
WHILE @@FETCH_STATUS = 0
BEGIN
set @Flage=0
If(@DataType in('bigint','numeric','bit','smallint','decimal','smallmoney','int','tinyint','money','float','real'))
begin
set @Flage=1
end
If(@DataType in('date','atetimeoffset','datetime2','smalldatetime','datetime','time'))
begin
set @Flage=2
end
If(@DataType in('char','varchar','text','nchar','nvarchar','ntext'))
begin
set @Flage=3
end
If(@DataType in('binary','varbinary'))
begin
set @Flage=4
end
DECLARE @SQL VARCHAR(MAX)
if (@Flage in(1,4))
begin
SET @SQL =' update ['+@TableName+'] set ['+@ColumnName+']=0 where ['+@ColumnName+'] is null'
end
if (@Flage =3)
begin
SET @SQL =' update ['+@TableName+'] set ['+@ColumnName+'] = '''' where ['+@ColumnName+'] is null '
end
if (@Flage =2)
begin
SET @SQL =' update ['+@TableName+'] set ['+@ColumnName+'] ='+'''1901-01-01 00:00:00.000'''+' where ['+@ColumnName+'] is null '
end
EXEC(@SQL)
FETCH NEXT FROM Cussor INTO @ColumnName,@TableName,@DataType
END
CLOSE Cussor
DEALLOCATE Cussor
END