SQL from Scratch: History, Theory, and Why It Remains the Language of Data
Few technologies have had such a long shelf life — and such a quietly pervasive influence — as SQL. While programming languages come and go with the t...
#2 SQLThe SELECT Statement: Reading Data from a Relational Database
If you ever plan to ask a question of a database, you will almost certainly begin with the word SELECT. It is the verb of SQL — the command that retri...
#3 SQLWhat Type Is That Column?
Every column in a database is, in a sense, a labelled box. The label tells the engine what may be stored inside, how much room to reserve, and how the...
#4 SQLSQL JOINs: Combining Data from Multiple Tables
Relational databases deliberately scatter information across many tables — a single customer here, their orders there, their addresses somewhere else....
#5 SQLFrom Rows to Insights: Aggregate Functions
A database that can only hand back individual rows is like a calculator that only displays the numbers you typed in. The real power of SQL appears whe...
#6 SQLQuestions Inside Questions: SQL Subqueries Explained
A subquery is a query nested inside another query — a small question whose answer feeds a larger one. Master the four places a subquery can live and y...
#7 SQLUnderstanding SQL Common Table Expressions
A Common Table Expression — or CTE — is a named temporary result set that exists only for the duration of a single query. It lets you take a complicat...
#8 SQLUnderstanding Temporary Tables
Imagine a whiteboard you wheel into a meeting. You scribble figures on it, refer back to them as the discussion unfolds, rearrange them — and when the...
