ORA-00906：“缺少左括号”

Question

我尝试添加一些约束，但无论我做什么，我都会收到这条消息，我错过了左括号..

1

alter table CUSTOMER
add unique customer.username (username);

2

ALTER TABLE CUSTOMER 
ADD CONSTRAINT CHECK customer.credit_type (credit_type,'high','average','low');

有什么想法吗？

提前致谢！

Answer 1

您似乎正在寻找这种语法：

ALTER TABLE customer
ADD CONSTRAINT username_unique UNIQUE (username);

ALTER TABLE customer
ADD CONSTRAINT check_credit_type CHECK (credit_type IN ('high','average','low'));