Avoid SELECT * in Production Queries

SELECT * fetches all columns, wasting bandwidth and preventing covering index optimization.

Why This Matters

Using SELECT * transfers unnecessary data, prevents the query optimizer from using covering indexes, and breaks if columns are added later.

Related Rules

Use Online DDL for ALTER TABLE

Performance

CRITICAL

Use utf8mb4 Instead of utf8

Architecture

MEDIUM

Index All Foreign Key Columns

Performance

HIGH

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Why This Matters

SELECT * is a common anti-pattern that:

Transfers more data than needed over the network
Prevents MySQL from using covering indexes (index-only scans)
Breaks applications when columns are added or reordered
Makes query intent unclear during code review

Detection

# Grep for SELECT * in application code
grep -rn "SELECT \*" --include="*.sql" --include="*.ts" --include="*.py"
 
# pt-query-digest can identify SELECT * in slow query logs
pt-query-digest /var/log/mysql/slow.log --filter '$event->{arg} =~ m/SELECT \*/i'

Fix

-- Bad
SELECT * FROM users WHERE id = 1;
 
-- Good: explicit columns
SELECT id, name, email FROM users WHERE id = 1;

Tools

SQLFluff rule AM04 (SELECT * usage)
pt-query-digest (Percona Toolkit) for production query analysis
SonarQube SQL analysis rules

Avoid SELECT * in Production Queries

Why This Matters

Tags

Related Rules

Catch this automatically on every PR

Why This Matters

Detection

Fix

Tools