Sql ORA-00906:；缺少左括号“；

我试图添加一些约束，但无论我做什么，我都会得到这样一个信息，我缺少左括号

一,

二,

有什么想法吗

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提前谢谢

您似乎在寻找以下语法：

ALTER TABLE customer
ADD CONSTRAINT username_unique UNIQUE (username);

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

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看起来您正在寻找以下语法：

ALTER TABLE customer
ADD CONSTRAINT username_unique UNIQUE (username);

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

ALTER TABLE customer
ADD CONSTRAINT username_unique UNIQUE (username);

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