如何定位列名的默认值约束

如何解决如何定位列名的默认值约束

我注意到，当默认值为“0001-01-01”且未提供有效日期时，数据库表中的某些日期列给我的 Power App 带来了困难（修补）。请注意，我不能只在我的 Power App 中设置默认值，因为其他应用程序正在使用 sql 表。

我目前的想法是我使用 Tsql 将默认值更改为“1001-01-01”，以便我可以尽可能地自动化。

1. 获取列的 (DF_TABLENAME_XXXX) 约束名称，然后将其推入变量 @mytablename
2. 删除此约束名称
3. 重新创建约束 ALTER TABLE @MyTable DEFAULT '1001-12-31' FOR @ColumnName

我在步骤 1) atm 中挣扎。此外，我很高兴采用比我概述的方法更好的方法。

解决方法

我前段时间写了这段代码来创建各种数据字典。它使用所有 sys 表来获取有关数据库中表的信息。只需更改最上面一行，您就应该准备就绪。

USE [INSERT YOUR DATABASE NAME HERE]
GO

SELECT
            DB_NAME() AS [DatabaseName],OBJECT_SCHEMA_NAME(TBL.[object_id],DB_ID()) AS [Schema],TBL.[name] AS [TableName],AC.[name] AS [ColumnName],UPPER(TY.[name]) AS [DataType],AC.[max_length] AS [Length],AC.[precision] AS [Precision],AC.[scale] AS [Scale],AC.[is_nullable] AS [IsNullable],ISNULL(SI.is_primary_key,0) AS [IsPrimaryKey],SKC.name AS [PrimaryKeyConstarint],CASE
                    WHEN SIC.index_column_id > 0
                            THEN 1
                    ELSE 0
                END AS [IsIndexed],ISNULL(is_included_column,0) AS [IsIncludedIndex],SI.name AS [IndexName],OBJECT_NAME(SFC.constraint_object_id) AS [ForeignKeyConstraint],OBJECT_SCHEMA_NAME(TBL_PRIM.[object_id],DB_ID()) AS [ParentTableSchema],OBJECT_NAME(SFC.referenced_object_id) AS [ParentTableName],COL_PRIM.name AS [ParentTableColumnName],DB_ID()) + '.' + TBL.[name] + '.' + AC.[name]
                + ' = ' + OBJECT_SCHEMA_NAME(TBL_PRIM.[object_id],DB_ID()) + '.'
                + OBJECT_NAME(SFC.referenced_object_id) + '.' + COL_PRIM.name AS [JoinCondition],SDC.name AS [DefaultConstraint],SDC.[definition] AS [DefaultValue],AC.collation_name AS [Collation],SEP.value AS [Comments]

FROM [sys].[tables] AS TBL

JOIN [sys].[all_columns] AS AC
        ON TBL.[object_id] = AC.[object_id]

JOIN [sys].[types] AS TY
        ON AC.[system_type_id] = TY.[system_type_id]
        AND AC.[user_type_id] = TY.[user_type_id]

LEFT JOIN [sys].[index_columns] AS SIC
        ON sic.[object_id] = TBL.[object_id]
        AND AC.column_id = SIC.column_id

LEFT JOIN [sys].[indexes] AS SI
        ON SI.[object_id] = TBL.[object_id]
        AND SIC.index_id = SI.index_id

LEFT JOIN [sys].[foreign_key_columns] AS SFC
        ON SFC.parent_object_id = TBL.[object_id]
        AND SFC.parent_column_id = AC.column_id

LEFT JOIN [sys].[key_constraints] AS SKC
        ON skc.parent_object_id = TBL.[object_id]
        AND SIC.index_column_id = SKC.unique_index_id

LEFT JOIN [sys].[default_constraints] AS SDC
        ON SDC.parent_column_id = AC.column_id

LEFT JOIN [sys].[extended_properties] AS SEP
        ON SEP.major_id = TBL.[object_id]
        AND SEP.minor_id = AC.column_id

LEFT JOIN [sys].[tables] AS TBL_PRIM
        ON SFC.referenced_object_id = TBL_PRIM.[object_id]

LEFT JOIN [sys].[columns] AS COL_PRIM
        ON SFC.referenced_object_id = COL_PRIM.[object_id]
        AND SFC.referenced_column_id = COL_PRIM.column_id

,

在 where 子句中填写问号，这将为您提供默认约束的名称。

SELECT
    SchemaName = SCH.[name],TableName = TAB.[name],ColumnName = COL.[name],DefaultConstraint = DFC.[name]
FROM sys.default_constraints AS DFC
    JOIN sys.columns AS COL
        ON DFC.parent_object_id = COL.[object_id]
            AND DFC.parent_column_id = COL.column_id
    JOIN sys.tables AS TAB
        ON COL.[object_id] = TAB.[object_id]
    JOIN SYS.schemas AS SCH
        ON TAB.[schema_id] = SCH.[schema_id]
WHERE SCH.[name] = ?
    AND TAB.[name] = ?
    AND COL.[name] = ?