SQL Joins in PostgreSQL: Patients, Doctors, and the Rows That Go Missing
A join is how you ask one question across two tables. The database keeps patients in one table and appointments in another, because storing the patient's name on every appointment row would mean fixing it in ten places when it's misspelled. A join puts them back together for the length of one query. That's the whole idea. The part that takes practice is that there are several kinds of joins, and…
A join is a method for combining data from two tables based on a related column. In a hospital database, patients are stored in one table, while appointments are stored in another. This allows queries to retrieve information from both tables simultaneously. Joins are an essential concept in SQL databases. They come in several types, each with its own behavior when dealing with rows that don't have a corresponding match in the other table.
This article uses a small hospital database containing 10 patients, 10 doctors, and 10 appointments to demonstrate the different types of joins and how they handle missing data.
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