唯一:ALTER TABLE TableName ADD CONSTRAINT UQ_NickName UNIQUE(NickName)
主键:ALTER TABLE TableName ADD CONSTRAINT PK_ID PRIMARY KEY(ID)
默认值:ALTER TABLE TableName ADD CONSTRAINT DF_Gender DEFAULT ('男') FOR Gender
check:ALTER TABLE TableName ADD CONSTRAINT CK_Age CHECK(Age>0)
外键:ALTER TABLE TableName ADD CONSTRAINT FK_ParentID FOREIGN KEY(ParentID) REFERENCES ParentTableName(ID)
移除约束:
ALTER TABLE [dbo].[S_USER] DROP CONSTRAINT UQ_U_NAME
sp_helpconstraint 表名 找到数据表中的所有列的约束