Prefer high-selectivity columns

sql

-- Better index candidate
WHERE email = ?

-- Often weaker candidate by itself
WHERE is_active = true

Explanation

An index on a highly selective column usually narrows results faster than an index on a low-cardinality flag.

Learn the surrounding workflow

Compare similar commands or jump into common fixes when this command is part of a bigger troubleshooting path.

Same sheet · prioritizing Core concepts

Indexes trade storage and write cost for faster reads.

Open In sheettextsame section

Every extra index must be maintained during inserts, updates, and deletes.

Open In sheettextsame section

Use column order that matches real filter patterns.

Open In sheetsqlsame section

Indexing is not just for filters.

Open In sheetsqlsame section

Use this checklist before creating a new index.

Validate improvement instead of guessing.