如何从数据库中的每个表中选择日期列？

Question

我试图从数据库中的每个日期列中选择最小日期。我的意思是最小值是我想获得最早的日期。

根据我的调查，似乎最好的方法是使用动态 SQL。这是我目前正在尝试的代码，但我无法从中得到任何东西。

DECLARE @Sql nvarchar(max) 

SELECT @Sql = STUFF(
        (       
            SELECT ' UNION ALL SELECT '''+ MIN(C.COLUMN_NAME) +','+''''+ C.TABLE_NAME +''' As TableName FROM '+ C.TABLE_SCHEMA+ '.' +C.TABLE_NAME
            FROM Information_schema.Columns C
            JOIN Information_schema.Tables T
            ON C.TABLE_NAME = T.TABLE_NAME
            WHERE C.DATA_TYPE in ('datetime','date','datetime2','timestamp','time')
                and C.TABLE_SCHEMA NOT IN ('STG','HIST')
                and C.TABLE_SCHEMA IN ('COSTOS')
                and T.TABLE_TYPE <> 'VIEW'
            GROUP BY C.TABLE_SCHEMA, C.TABLE_NAME
            FOR XML PATH('')
        ), 1, 11, '')

EXEC(@Sql)
SELECT @Sql 

我不熟悉动态 SQL，该查询的输出是空结果。

Answer 1

这是基于您的尝试，您需要做的一件事是将

MIN()

放入语句中：

DECLARE @sql nvarchar(max) 
DECLARE @err int

SELECT @sql = STUFF(
    (
    SELECT 
        'UNION ALL SELECT ' +
        QUOTENAME(C.TABLE_NAME, '''') + ' AS [TableName], ' +
        QUOTENAME(C.TABLE_SCHEMA, '''') + ' AS [SchemaName], ' +
        QUOTENAME(C.COLUMN_NAME, '''') + ' AS [ColumnName], ' +
        'MIN(' + QUOTENAME(C.COLUMN_NAME) + ') AS [ColumnValue] '  +
        'FROM ' + QUOTENAME(C.TABLE_SCHEMA) + '.' + QUOTENAME(C.TABLE_NAME) + ' '
    FROM Information_schema.Columns C
    JOIN Information_schema.Tables T ON C.TABLE_NAME = T.TABLE_NAME
    WHERE 
        C.DATA_TYPE IN ('datetime','date','datetime2','timestamp','time')
        AND C.TABLE_SCHEMA NOT IN ('STG','HIST')
        AND C.TABLE_SCHEMA IN ('COSTOS')
        AND T.TABLE_TYPE <> 'VIEW'
    FOR XML PATH(''), TYPE
    ).value('text()[1]', 'nvarchar(max)'), 1, 10, '')

PRINT @sql
EXEC @err = sp_executesql @sql