Module 2. Lesson 2. Selecting Specific Columns

Description:
Selecting Specific Columns
Picking the right columns is one of the simplest habits that separates a tidy analyst from a sloppy one.

Why it matters
Performance — less data shipped = faster queries, especially on big tables
Clarity — the next person reading your query immediately understands intent
Stability — your downstream report won't break when a DBA adds a new column
Privacy — you avoid accidentally exposing sensitive fields (e.g. national ID, DOB)
A focused query
This is enough for a price list. There is no reason to also pull supplier IDs, image URLs, or warehouse locations you don't need.

Reordering and computed columns
You can list columns in any order, and you can compute new ones on the fly: PriceIncVAT doesn't exist in the table — SQL calculates it for each row in the result.