SQL删除列、查找外键约束、删除约束语句实例讲解

alter table tableName drop column columnName  --(其中，tableName为表名，columnName为列名)

DECLARE @TableName NVARCHAR(64) = ''
DECLARE @ColumnName  NVARCHAR(32) = ''SELECT c.name FROM sysconstraints a 
inner join syscolumns b on a.colid=b.colid 
inner join sys s c on a.constid=c.id
where a.id= _id(@TableName) 
and b.name=@ColumnName

ALTER TABLE @TableName DROP CONSTRAINT @CONSTRAINT_NAME

DECLARE @TableName NVARCHAR(64) = ''
DECLARE @ColumnName  NVARCHAR(32) = ''
DECLARE @CONSTRAINT_Key SYSNAME
SELECT @CONSTRAINT_Key = c.name FROM sysconstraints a 
inner join syscolumns b on a.colid=b.colid 
inner join sys s c on a.constid=c.id
where a.id= _id(@TableName) 
and b.name=@ColumnName
DECLARE @Sql NVARCHAR(512) = N'ALTER TABLE ' + @TableName + ' DROP CONSTRAINT ' + @CONSTRAINT_Key
EXECUTE sys.sp_executesql @Sql