IF EXISTS(SELECT TOP 1 1 FROM sys.default_constraints WHERE parent_object_id = OBJECT_ID(N'[dbo].[ChannelPlayerSkins]') AND name = 'FK_ChannelPlayerSkins_Channels')
BEGIN
    DROP CONSTRAINT FK_ChannelPlayerSkins_Channels
END
GO

试试这个:

SELECT
    * 
    FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS 
    WHERE CONSTRAINT_NAME ='FK_ChannelPlayerSkins_Channels'

——编辑——

当我最初回答这个问题时，我在想“外键”，因为最初的问题要求找到“FK_ChannelPlayerSkins_Channels”。从那时起，许多人就寻找其他“约束”发表了评论，这里有一些其他的查询:

--Returns one row for each CHECK, UNIQUE, PRIMARY KEY, and/or FOREIGN KEY
SELECT * 
    FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS
    WHERE CONSTRAINT_NAME='XYZ'  


--Returns one row for each FOREIGN KEY constrain
SELECT * 
    FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS 
    WHERE CONSTRAINT_NAME='XYZ'


--Returns one row for each CHECK constraint 
SELECT * 
    FROM INFORMATION_SCHEMA.CHECK_CONSTRAINTS
    WHERE CONSTRAINT_NAME='XYZ'

这里有一个替代方法

--Returns 1 row for each CHECK, UNIQUE, PRIMARY KEY, FOREIGN KEY, and/or DEFAULT
SELECT 
    OBJECT_NAME(OBJECT_ID) AS NameofConstraint
        ,SCHEMA_NAME(schema_id) AS SchemaName
        ,OBJECT_NAME(parent_object_id) AS TableName
        ,type_desc AS ConstraintType
    FROM sys.objects
    WHERE type_desc LIKE '%CONSTRAINT'
        AND OBJECT_NAME(OBJECT_ID)='XYZ'

If you need even more constraint information, look inside the system stored procedure master.sys.sp_helpconstraint to see how to get certain information. To view the source code using SQL Server Management Studio get into the "Object Explorer". From there you expand the "Master" database, then expand "Programmability", then "Stored Procedures", then "System Stored Procedures". You can then find "sys.sp_helpconstraint" and right click it and select "modify". Just be careful to not save any changes to it. Also, you can just use this system stored procedure on any table by using it like EXEC sp_helpconstraint YourTableNameHere.

IF (OBJECT_ID('FK_ChannelPlayerSkins_Channels') IS NOT NULL)

从SQL Server 2016开始，你可以只使用IF EXISTS关键字。

ALTER TABLE dbo.ChannelPlayerSkins
    DROP CONSTRAINT IF EXISTS FK_ChannelPlayerSkins_Channels

我使用的是SQL Server 2019，但这里提到它自SQL Server 2016以来就可用了。

SQL Server文档在ALTER TABLE页面下提到了它，而不是在Delete Check Constraints页面下。我不知道为什么。

如果存在 适用于:SQL Server (SQL Server 2016 (13.x)及以上版本)、Azure SQL数据库。 只有当列或约束已经存在时，才有条件地删除它。

我使用它来检查和远程列上的约束。它应该有你需要的一切。

DECLARE
  @ps_TableName VARCHAR(300)
  , @ps_ColumnName VARCHAR(300)

SET @ps_TableName = 'mytable'
SET @ps_ColumnName = 'mycolumn'

DECLARE c_ConsList CURSOR LOCAL STATIC FORWARD_ONLY FOR
    SELECT
    'ALTER TABLE ' + RTRIM(tb.name) + ' drop constraint ' + sco.name AS csql
    FROM
        sys.Objects tb
        INNER JOIN sys.Columns tc on (tb.Object_id = tc.object_id)
        INNER JOIN sys.sysconstraints sc ON (tc.Object_ID = sc.id and tc.column_id = sc.colid)
        INNER JOIN sys.objects sco ON (sc.Constid = sco.object_id)
    where
        tb.name=@ps_TableName
        AND tc.name=@ps_ColumnName
OPEN c_ConsList
FETCH c_ConsList INTO @ls_SQL
WHILE (@@FETCH_STATUS = 0) BEGIN

    IF RTRIM(ISNULL(@ls_SQL, '')) <> '' BEGIN
        EXECUTE(@ls_SQL)
    END
    FETCH c_ConsList INTO @ls_SQL
END
CLOSE c_ConsList
DEALLOCATE c_ConsList

你在看类似这样的东西吗，下面是在SQL Server 2005中测试的

SELECT * FROM sys.check_constraints WHERE 
object_id = OBJECT_ID(N'[dbo].[CK_accounts]') AND 
parent_object_id = OBJECT_ID(N'[dbo]. [accounts]')