lyfz_repos/经典版源码/document/SQL常用语句.sql

---添加主键约束 
AFTER TABLE [表名] ADD CONSTRAINT [PK_约束名] PRIMARY KEY([字段1],[字段2],[..])  
--示例:
Alter Table stuInfo Add Constraint PK_stuNO primary Key(stuNo)   

---添加唯一约束   
ALTER TABLE [表名] ADD CONSTRAINT [UK_约束名] UNIQUE([字段1],[字段2],[..])
--示例:
Alter Table stuInfo Add Constraint UQ_stuID unique(stuID)   

---添加默认值约束   
ALTER TABLE [表名] ADD CONSTRAINT [DF_约束名] DEFAULT(默认值) FOR [字段]
--示例:
Alter Table stuInfo  Add Constraint DF_stuAddress default('地址不详') for stuAddress   

---添加条件检查约束  
ALTER TABLE [表名] ADD CONSTRAINT [CK_约束名] CHECK(条件表达式) 
--示例:
Alter Table stuInfo  Add Constraint CK_stuAge check(stuAge between 15 and 40)   

---添加外键约束   
ALTER TABLE [表名] ADD CONSTRAINT [FK_约束名] FOREIGN KEY[字段名] REFERENCES [外键所在表名].[字段名]
--示例:
Alter Table stuMarks  Add Constraint FK_stuNo foreign key(stuNo) references stuInfo(stuNo)