primary key « mysql « Java Database Q&A

1. Is it possible to reference the same primary key for 2 foreign keys in mySQL? I keep getting an error message whenever I try    stackoverflow.com

The first 2 go through without a hitch, but when I try to do the last one, I get this error message: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a ...

2. "No primary keys" error in NetBeans    stackoverflow.com

In NetBeans7 when I'm trying to add "Entity Classes from Database" the following problem occurs: some of the tables on the left are greyed out and marked "(no primary keys)", so ...

3. MySql primary keys    coderanch.com

4. 2 primary keys with mysql    coderanch.com

Hi guys, I have a table with the following columns: 1. Id (auto-inc) and primary 2. Email - primary 3. Password (When looking at the table i can see 2 keys symbolizing the primary keys) Anyway, how come, when I INSERT 2 equal emails - the system write it. Doesnt it suppose to throw an exception? I'm trying to have unique ...

5. Timestampt as a primary key in MySQL    coderanch.com

Hi! I am working on app which should work somthing like a gas storage optimizer, one day hopefully. Now I am trying to implement a storage as a MySQL table with timestamp as a primary key. So I should be able to refer any hour in next three years for example, and to get available capacity of storage, injection and withdrawal ...