Alter Constraint 命令

约束条件

ALTER TABLE table

ADD [CONSTRAINT constraint] type (column);
ALTER TABLE table

DROP { PRIMARY KEY | UNIQUE (column) | CONSTRAINT constraint }

[CASCADE];
ALTER TABLE table

ENABLE CONSTRAINT constraint;
ALTER TABLE table

DISABLE CONSTRAINT constraint;

type 约束类型

约束 语法
唯一约束 UNIQUE( column [,...] )
主键约束 PRIMARY KEY 
外键约束 FOREIGN KEY( ) REFERENCES ( )
检查约束 CHECK (condition) [,...]

查看已有的约束

SELECT constraint_name, constraint_type,
search_condition
FROM user_constraints
WHERE table_name = 'table_name';