在许多列上删除SQL Server中的默认约束

Question

对于SQL Server 2008 R2，我想删除允许为null且约束包含1899的日期列的默认约束。并且我想要一个可以在现场执行测试并执行的脚本。我不想在现场环境中摆弄这个。另一个原因是脚本是，有几个数据库具有相同的方案

的帮助谷歌从我有以下脚本列表列

SELECT tables.name, all_columns.name, all_columns.is_nullable, default_constraints.name, default_constraints.definition 
FROM 
    sys.all_columns 
     INNER JOIN 
    sys.tables 
     ON all_columns.object_id = tables.object_id 
     INNER JOIN 
    sys.schemas 
     ON tables.schema_id = schemas.schema_id 
     INNER JOIN 
    sys.default_constraints 
     ON all_columns.default_object_id = default_constraints.object_id 
WHERE 
     schemas.name = 'dbo' 
    and default_constraints.definition like '%1899%' 
    and all_columns.is_nullable = 1 
order by tables.name, all_columns.name, default_constraints.name 

现在，这个名单超过百柱。下一个脚本按照CargoPool.Created列的要求进行操作。但是，我怎样才能迭代从我的第一个脚本创建的所有行？

DECLARE @tableName VARCHAR(MAX) = 'CargoPool' 
DECLARE @columnName VARCHAR(MAX) = 'Created' 
DECLARE @ConstraintName nvarchar(200) 
SELECT @ConstraintName = Name 
FROM SYS.DEFAULT_CONSTRAINTS 
WHERE PARENT_OBJECT_ID = OBJECT_ID(@tableName) 
AND PARENT_COLUMN_ID = (
    SELECT column_id FROM sys.columns 
    WHERE NAME = @columnName AND object_id = OBJECT_ID(@tableName)) 
IF @ConstraintName IS NOT NULL 
    EXEC('ALTER TABLE '+@tableName+' DROP CONSTRAINT ' + @ConstraintName) 

Answer 1

如果你想从你的第一个查询删除所有限制，你可以建立一个动态SQL与查询的结果，然后执行：

DECLARE @sql AS NVARCHAR(MAX) = N'' 

SELECT @sql = @sql + N'ALTER TABLE ' 
     + QUOTENAME(schemas.name) + N'.' + QUOTENAME(tables.name) 
     + N' DROP CONSTRAINT ' + QUOTENAME(default_constraints.name) + N'; ' 
FROM 
    sys.all_columns 
     INNER JOIN 
    sys.tables 
     ON all_columns.object_id = tables.object_id 
     INNER JOIN 
    sys.schemas 
     ON tables.schema_id = schemas.schema_id 
     INNER JOIN 
    sys.default_constraints 
     ON all_columns.default_object_id = default_constraints.object_id 
WHERE 
     schemas.name = N'dbo' 
    and default_constraints.definition like N'%1899%' 
    and all_columns.is_nullable = 1 
order by tables.name, all_columns.name, default_constraints.name 

exec sp_executesql @sql;