Queries others can read.
WHAT MAKES SQL UNMAINTAINABLE
Very long single queries Deeply nested subqueries No formatting convention Cryptic aliases Business logic repeated across files
WHAT TO ADOPT
A formatter, applied automatically A naming convention for aliases Structuring with named steps
WHAT TO NAME ALIASES
Meaningfully, not single letters.
WHY
A query with five single-letter aliases is unreadable within a month.
WHAT TO COMMENT
Why, not what.
WHAT TO EXTRACT
Repeated logic into shared models or views.
WHY
So a definition change happens once.
WHAT TO TEST
That results match expectations for known inputs That row counts are as expected That keys are unique where they should be
WHAT TO VERSION CONTROL
Every query that matters.
WHY
Queries pasted into tools and lost are how knowledge disappears.
WHAT TO REVIEW
SQL, as you would review any other code.
WHAT TO CHECK IN REVIEW
Correctness of joins and grain Whether filters behave as intended Whether it will still work as data grows
