'How to create a unique number in java before sending an SQL query [duplicate]

I am making an app in java that sends SQL queries. The user can propose a room that others can book. To propose a room, the user has to fill a form. When the user fills the form and presses on the validate button, the app create an SQL query that insert the inputted information in a table proposedRoom.

However each proposed room in my table has a primary key, proposedRoomId which is an int. I am having trouble creating that primary key in Java before sending the Query to insert the room in the table.

What I tried to do is using the date to generate the corresponding integer, but if two people happen to propose a room at the same time it will cause error. I thought about hashing and changing the type of the key to String but this seems complicated and may reduce my app performance.

javasqlkeyunique


Solution 1:[1]

If you have access to the DBMS, you can alter the definition of proposedRoomId column and add AUTO_INCREMENT to it. Then you need not worry about that.

I've no idea how things work with JDBC but there must be some way to get LAST_INSERT_ID too.

Solution 2:[2]

You can take the following approaches:

  1. If you can convert proposedRoomId to String, try using UUID.
  2. Try to create hash by taking a combination of RoomID and UserID.
  3. Try to create hash by taking combination of timestamp and RoomID.

Sources

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Source: Stack Overflow

Solution Source
Solution 1 Hemanth788
Solution 2 Prakul

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