Question

I have table as below

personalInfo

CREATE TABLE personalInfo(userid BIGINT AUTO_INCREMENT PRIMARY KEY)

patentInfo

CREATE TABLE patentInfo 
(
 userid BIGINT,
 patentId BIGINT AUTO_INCREMENT,
 FOREIGN KEY (userid) REFERENCES personalInfo(userid), 
 PRIMARY KEY (userid,patentId)
)

While creating table patentInfo, I am getting error as

Incorrect table definition; there can be only one auto column and it must be defined as a key.

What I want to do is add patent for Users. So I was trying to use patentId as AUTO_INCREMENT and keep compiste primary key as combination of patentId & userid.

Any idea how can I get this done?

Update 1:

My AIM is, I don’t want to insert patentId in mysql query. mysql itself will create next number.

Answer 1

Since patentId is AUTO_INCREMENT, then the it should be the primary key.