Querying Databases: WHERE and JOIN in SQL

Imagine a school library keeps two lists. The first list has every student's name and their student ID number. The second list has every borrowed book and the student ID of the person who borrowed it. Could you figure out which student has which book? Of course — you match the ID numbers. That matching idea is exactly what SQL does for you automatically. Before you dive in, think about this: if you had a list of 10,000 students, how would you quickly find just the ones in Year 9? You need a way to filter. SQL gives you two powerful tools for exactly these tasks: WHERE and JOIN.