每个用作 CHECK 约束（sys.objects.type = C）的对象都在表中占一行。
SELECT name FROM sys.check_constraints -- equal to SELECT o.name FROM sys.sysobjects o JOIN sys.sysconstraints s ON o.parent_obj = s.id WHERE o.xtype = ‘C‘ GROUP BY o.name
sys.check_constraints (Transact-SQL)
原文：http://www.cnblogs.com/niaomingjian/p/4658622.html