SQL Review

• Injection — parameterized, always. No string interpolation into SQL.
• N+1 — a query inside a loop? Replace with a join or a batched IN.
• Missing index — does the WHERE/JOIN/ORDER BY hit an indexed column? If not, the table scan will surface at scale.
• Unbounded — SELECT with no LIMIT on a growing table; a JOIN that fans out rows.
• Transactions — multi-write operations wrapped so a partial failure can't corrupt state.
• Migrations — reversible (up AND down), and safe on a live table (no blocking lock on a hot table at peak). Output: each issue with the line and the rewrite. Show the EXPLAIN if performance is the concern.