Whenever I dig into a new database, I check the data type specified for each column in each table. If I’m lucky, I can get my hands on a data dictionary: a document that lists each column; specifies whether it’s a number, character, or other type; and explains the column values. Unfortunately, many organizations don’t create and maintain good documentation, so it’s not unusual to hear, “We don’t have a data dictionary.” In that case, I try to learn by inspecting the table structures in pgAdmin.

It’s important to understand data types because storing data in the appropriate format is fundamental to building usable databases ...

Get Practical SQL now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.