在不知道约束名称的情况下删除列上的约束

Question

我想在多个数据库中的列上删除一个约束。我不知道列上约束的确切名称。

是否可以在不知道其名称的情况下删除约束。

例如： ALTER TABLE TempTable DROP CONSTRAINT IF EXISTS ON Columnname

Answer 1

您可以从这样的表中检索约束信息

select t.Name as TableName,
       ccd.Name as ColumnName_default_constraint,
       dc.Name as default_constraint,
       ccc.Name as ColumnName_check_constraint,
       cc.Name as check_constraint
from   sys.tables t
  inner join sys.default_constraints dc on t.object_id = dc.parent_object_id
  inner join sys.check_constraints cc on t.object_id = cc.parent_object_id
  inner join sys.columns ccd on dc.parent_object_id = ccd.object_id 
                          and ccd.column_id = dc.parent_column_id
  inner join sys.columns ccc on cc.parent_object_id = ccc.object_id 
                          and ccc.column_id = cc.parent_column_id
where t.Name = 'your table name'
order by t.Name

从这里你可以构建这样的脚本

select 'alter table ' + t.Name +' drop constraint ' + dc.Name,
       'alter table ' + t.Name +' drop constraint ' + cc.Name
from   sys.tables t
  inner join sys.default_constraints dc on t.object_id = dc.parent_object_id
  inner join sys.check_constraints cc on t.object_id = cc.parent_object_id
where t.Name = 'your table name'
order by t.Name