You need the following tables:-

Login table with three fields:- UniqueID, (autonumber), Username, (text), password, (text)

Jobs table with a UniqueID, (autonumber), UserID (long integer), and any other firlds you require for the job details

Go to "Create a new Query", select the two tables so they appear in the top area. left click and hold the UniqueID field in the Login table and drag it to the UserID field in the Jobs table. You will see a line join the two fields with an arrow at the Jobs table end. This is called a relationship.

Then drag the UserID and Username fields down into the grid at the bottom along with any fields you want for the results. When you put a userID in the "criteria" area and run the query then the results will only be those belonging to the UserID selected.

Now you can incorporate that query in any number of ways into your app.