Sql server 如何查找数据库中未使用的列（SQLServer2008）。

保留为空/null/space或零的列（给定一个表列表）

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假设我可以从中央系统表中提取表和列定义，我应该如何检查上述条件

SQL Server内部没有特殊的过程来进行此确定。您需要查询每个表。以下是一个暴力解决方案：

If object_id('tempdb..#Results') is not null
    Drop Table #Results;
GO
Create Table #Results
    (
    TableSchema sysname not null
    , TableName sysname not null
    , ColumnName sysname not null
    );
GO

Declare @TableSchema sysname;
Declare @TableName sysname;
Declare @ColumnName sysname;
Declare @DataType sysname;
Declare @Columns Cursor;
Declare @BaseSql nvarchar(max);
Declare @Sql nvarchar(max);
Declare @AdditionalFilter nvarchar(max);

Set @BaseSql = 'Insert #Results( TableSchema, TableName, ColumnName )
                Select ''TABLE_SCHEMA'', ''TABLE_NAME'', ''COLUMN_NAME''
                From ( Select 1 As V ) As Z
                Where Not Exists    (
                                    Select 1
                                    From [TABLE_SCHEMA].[TABLE_NAME]
                                    Where [COLUMN_NAME] Is Not Null
                                        ADDITIONAL_FILTER
                                    )';

Set @Columns = Cursor Fast_Forward For
    Select C.TABLE_SCHEMA, C.TABLE_NAME, C.COLUMN_NAME, C.DATA_TYPE
    From INFORMATION_SCHEMA.COLUMNS As C
        Left Join INFORMATION_SCHEMA.VIEWS As V
            On V.TABLE_SCHEMA = C.TABLE_SCHEMA
                And V.TABLE_NAME = C.TABLE_NAME
    Where V.TABLE_NAME Is Null;

Open @Columns;
Fetch Next From @Columns Into @TableSchema, @TableName, @ColumnName, @DataType;

While @@Fetch_Status = 0
Begin
    If @DataType In('int','smallint','tinyint','bigint','numeric','bit','decimal','money','smallmoney','float','real')
        Set @AdditionalFilter = 'And [COLUMN_NAME] <> 0';
    Else If @DataType In('char','nchar','varchar','nvarchar','text','ntext')
        Set @AdditionalFilter = 'And Len([COLUMN_NAME]) > 0';
    Else
        Set @AdditionalFilter = '';

    Set @Sql = Replace(@BaseSql, 'ADDITIONAL_FILTER', @AdditionalFilter);
    Set @Sql = Replace(@Sql, 'TABLE_SCHEMA', @TableSchema);
    Set @Sql = Replace(@Sql, 'TABLE_NAME', @TableName);
    Set @Sql = Replace(@Sql, 'COLUMN_NAME', @ColumnName);

    --Print @Sql
    Exec(@Sql)
    Fetch Next From @Columns Into @TableSchema, @TableName, @ColumnName, @DataType;
End

Close @Columns;
Deallocate @Columns;

Select *
From #Results

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对于数据库调优非常有用（我有很多未使用的列，我应该删除：S）。我刚刚在最后一个SELECT中添加了数据类型和orderby。谢谢运行上述代码时出现“参数数据类型文本对于len函数的参数1无效”。使用DATALENGTH是否更好？@adolfgarlic-您也可以使用

DATALENGTH

函数。我怀疑Len函数可能会在

text

和

ntext

数据类型上出现错误。

Set @BaseSql = 'Insert #Results( TableSchema, TableName, ColumnName )
                Select ''TABLE_SCHEMA'', ''TABLE_NAME'', ''COLUMN_NAME''
                From ( Select 1 As V ) As Z
                Where Exists    (
                                Select 1
                                From [TABLE_SCHEMA].[TABLE_NAME]
                                )
                And Not Exists  (
                                Select 1
                                From [TABLE_SCHEMA].[TABLE_NAME]
                                Where [COLUMN_NAME] Is Not Null
                                    ADDITIONAL_FILTER
                                )';