001: 16625
003: Starlibrary PMS 4.5
005: 20180430
066: ^aMa.u
072: ^aintroducing relational databases
082: ^a001.6
100: ^aMartin Gruber
240: ^aunderstanding sql
245: ^aunderstanding sql
260: ^c1990
650: ^asql: an overview
650: ^ausing sql to retrieve information from tables