这比目前提出的解决方案简单得多:

IF (OBJECT_ID('dbo.FK_ConstraintName', 'F') IS NOT NULL)
BEGIN
    ALTER TABLE dbo.TableName DROP CONSTRAINT FK_ConstraintName
END

如果你需要删除另一种类型的约束，这些是传入OBJECT_ID()函数的第二个参数位置的适用代码:

C = CHECK constraint
D = DEFAULT (constraint or stand-alone)
F = FOREIGN KEY constraint
PK = PRIMARY KEY constraint
UQ = UNIQUE constraint

也可以使用不带第二个参数的OBJECT_ID。

完整的类型列表在这里:

对象类型:

AF = Aggregate function (CLR) C = CHECK constraint D = DEFAULT (constraint or stand-alone) F = FOREIGN KEY constraint FN = SQL scalar function FS = Assembly (CLR) scalar-function FT = Assembly (CLR) table-valued function IF = SQL inline table-valued function IT = Internal table P = SQL Stored Procedure PC = Assembly (CLR) stored-procedure PG = Plan guide PK = PRIMARY KEY constraint R = Rule (old-style, stand-alone) RF = Replication-filter-procedure S = System base table SN = Synonym SO = Sequence object

适用于:SQL Server 2012 ~ SQL Server 2014。

服务队列 TA =组装(CLR) DML触发器 TF = SQL表值函数 SQL DML触发器 TT =表类型 U =表(自定义) UQ = UNIQUE约束 V =视图 扩展存储过程

所有表约束都存储在INFORMATION_SCHEMA中。TABLE_CONSTRAINTS

IF EXISTS(SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS C WHERE C.CONSTRAINT_NAME = '<CONSTRAINT NAME>' AND C.TABLE_NAME = '<TABLE NAME>')
BEGIN
    ALTER TABLE <TABLE NAME>
        DROP CONSTRAINT <CONSTRAINT NAME>
END
GO

在SQL Server 2016中，你可以使用DROP IF EXISTS:

CREATE TABLE t(id int primary key, 
               parentid int
                    constraint tpartnt foreign key references t(id))
GO
ALTER TABLE t
DROP CONSTRAINT IF EXISTS tpartnt
GO
DROP TABLE IF EXISTS t

见https://web.archive.org/web/20151105064708/http: / / blogs.msdn.com/b/sqlserverstorageengine/archive/2015/11/03/drop——如果存在-新- sql - server - 2016. - aspx

您可以使用这些查询为您的表查找所有fk。

Declare @SchemaName VarChar(200) = 'Schema Name'
Declare @TableName VarChar(200) = 'Table name'

-- Find FK in This table.
SELECT 
    'IF  EXISTS (SELECT * FROM sys.foreign_keys WHERE object_id = OBJECT_ID(N''' + 
      '[' + OBJECT_SCHEMA_NAME(FK.parent_object_id) + '].[' + FK.name + ']' 
      + ''') AND parent_object_id = OBJECT_ID(N''' + 
      '[' + OBJECT_SCHEMA_NAME(FK.parent_object_id) + '].[' 
      + OBJECT_NAME(FK.parent_object_id) + ']' + ''')) ' +

    'ALTER TABLE ' +  OBJECT_SCHEMA_NAME(FK.parent_object_id) +
    '.[' + OBJECT_NAME(FK.parent_object_id) + 
    '] DROP CONSTRAINT ' + FK.name
    , S.name , O.name, OBJECT_NAME(FK.parent_object_id)
FROM sys.foreign_keys AS FK
INNER JOIN Sys.objects As O 
  ON (O.object_id = FK.parent_object_id )
INNER JOIN SYS.schemas AS S 
  ON (O.schema_id = S.schema_id)  
WHERE 
      O.name = @TableName
      And S.name = @SchemaName


-- Find the FKs in the tables in which this table is used
  SELECT 
    ' IF  EXISTS (SELECT * FROM sys.foreign_keys WHERE object_id = OBJECT_ID(N''' + 
      '[' + OBJECT_SCHEMA_NAME(FK.parent_object_id) + '].[' + FK.name + ']' 
      + ''') AND parent_object_id = OBJECT_ID(N''' + 
      '[' + OBJECT_SCHEMA_NAME(FK.parent_object_id) + '].[' 
      + OBJECT_NAME(FK.parent_object_id) + ']' + ''')) ' +

    ' ALTER TABLE ' +  OBJECT_SCHEMA_NAME(FK.parent_object_id) +
    '.[' + OBJECT_NAME(FK.parent_object_id) + 
    '] DROP CONSTRAINT ' + FK.name
    , S.name , O.name, OBJECT_NAME(FK.parent_object_id)
FROM sys.foreign_keys AS FK
INNER JOIN Sys.objects As O 
  ON (O.object_id = FK.referenced_object_id )
INNER JOIN SYS.schemas AS S 
  ON (O.schema_id = S.schema_id)  
WHERE 
      O.name = @TableName
      And S.name = @SchemaName 

Declare @FKeyRemoveQuery NVarchar(max)

IF EXISTS(SELECT 1 FROM sys.foreign_keys WHERE parent_object_id = OBJECT_ID(N'dbo.TableName'))

BEGIN
    SELECT @FKeyRemoveQuery='ALTER TABLE dbo.TableName DROP CONSTRAINT [' + LTRIM(RTRIM([name])) + ']'   
    FROM sys.foreign_keys
    WHERE parent_object_id = OBJECT_ID(N'dbo.TableName')

    EXECUTE Sp_executesql @FKeyRemoveQuery 

END

这在Azure Sql服务器上工作得很顺利:

    IF (OBJECT_ID('dbo.FK_company_id', 'F') IS NOT NULL)
    BEGIN
    ALTER TABLE dbo.table_company DROP CONSTRAINT FK_company_id
    END