Understanding SQL query structure

This is basically SQL’s version of BODMAS/PEDMAS.

We write SQL one way…
but SQL executes it differently.

The golden rule:

F/JWGBHSOL/O

Looks gibberish at first.
Actually very important.

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How SQL Executes Queries

F/J → FROM / JOIN

Build the dataset.

• FROM → grab the main table
• JOIN → combine other tables

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W → WHERE

First filter.

Removes rows that don’t match conditions.

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GB → GROUP BY

Create groups from rows.

Turns row-level data into grouped data.

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H → HAVING

Second filter.

But this time for groups, not rows.

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S → SELECT

Pick the final columns/results to display.

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O → ORDER BY

Sort the final output.

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L/O → LIMIT / OFFSET

• LIMIT → how many rows to show
• OFFSET → how many rows to skip

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Important Thing

We WRITE SQL like this:

SELECT → FROM → WHERE

But SQL THINKS like this:

FROM → WHERE → GROUP BY → HAVING → SELECT → ORDER BY

Understanding this makes SQL much less confusing.

Reference: SQL ORDER OF EXECUTION