sql-review

SQL Review

Review uncommitted SQL changes against a catalog of patterns that cause real production incidents — masked errors, unindexed new tables, silent truncation, SQL injection, deadlock-prone CATCH blocks — and surface findings as recommendations the user can act on, without editing SQL unprompted.

When to use this skill

• "/sql-review" / "review my SQL" / "review the SQL diff"
• "lint the SQL" / "SQL pre-commit check" / "check my SQL changes"
• "audit my stored proc" / "any SQL antipatterns in this diff"
• Before committing a .sql change touching a stored procedure, function, or table

Do not auto-trigger when the user is asking for a general code review on a mixed diff — defer to code-review for that. This skill is specifically for SQL-heavy diffs where the antipattern catalog applies.

Hard rule: surface, don't refactor

If you find issues, do not start editing the SQL. Produce the findings report first. After delivering it, ask the user per finding: "Want me to fix #N?" — and wait for an explicit yes. Pre-authorization ("fix them all") proceeds through the list; absent that, default to ask-per-fix.

SQL changes are particularly sensitive because they often run against production data in a single non-reversible deployment. A drive-by refactor mid-review is more dangerous here than in application code.

Workflow

1. Snapshot the SQL diff. Run in parallel:
   • git status --short — see what's modified, staged, untracked.
   • git diff -- '*.sql' — unstaged SQL changes.
   • git diff --staged -- '*.sql' — staged SQL changes.
   • If user passed an explicit range (e.g. main..HEAD), use that instead: git diff -- '*.sql'.
2. Triage files into two buckets:
   • New files (status A or ??) — review the entire file. The whole file is new code; pre-existing antipatterns elsewhere don't apply.
   • Modified files (status M) — review only the changed hunks. The rest of the file may have legacy antipatterns the user isn't introducing (e.g. existing repos commonly have dozens of SPs with the sp_send_dbmail-in-CATCH pattern; flagging all of them on an unrelated edit creates noise).
3. For each check in What to check, look for the pattern in the relevant scope (whole file for new files, diff hunks for modified files). Use ripgrep — don't try to fully parse SQL.
4. Categorize each finding as BLOCKER / WARN / INFO (see Categories).
5. Cite file:line for every finding. Line numbers come from the diff or the current file content.
6. Produce the report in the Output format.
7. Offer to fix the suggested findings. Wait for the user's selection before editing.

Categories

• BLOCKER — would cause a production incident: silent data loss, masked errors, SQL injection, unindexed table that will grow, broken transaction handling. Fix before commit.
• WARN — likely a bug or maintenance hazard: NOLOCK in write paths, hardcoded environment values, missing SET NOCOUNT ON, cross-DB references. Should fix but won't necessarily incident.
• INFO — style / convention / hygiene: vestigial comments, cursor defaults, missing GRANT EXECUTE where the project's pattern exists.

Lead each finding with the why. "This swallows the original error and surfaces a misleading permission denial" beats "add ;THROW;".

Pattern hit ≠ finding

The 17 checks are pattern matches. A ripgrep hit is a candidate — before reporting it, Read the whole procedure/batch it sits in; severity depends on context the pattern can't see. Concrete demotions:

• WITH (NOLOCK) hit, but the proc is a read-only reporting proc with no INSERT/UPDATE/DELETE → WARN at most, not BLOCKER (check #13 blocks only when the same proc writes the tables it dirty-reads).
• DECLARE @retry with no WHILE @retry in sight → check for a GOTO-label retry loop consuming it before flagging; only report when nothing reads the variable.
• New CREATE TABLE with no index, but it's a static lookup/config table seeded with a handful of rows in the same diff → WARN with a one-line reason, not BLOCKER (the deadlock incident needs growth under concurrent writes).

Every reported finding must:

1. Quote the offending SQL verbatim — the exact line(s) from the file, not a paraphrase. Severity turns on exact tokens.
2. For BLOCKER / WARN: state the concrete production incident in one sentence (this state → this outcome, e.g. "first deadlock under load → SP silently gives up, rows never written"). If you can't write that sentence after reading the full proc, demote one level.

Zero findings is a valid outcome — a clean diff gets a clean report. Never stretch INFO items into WARNs to fill sections; thoroughness is the 17 checks you ran, which the report shows.

What to check

Use ripgrep for detection. The patterns below are starting points — adapt to the actual diff text.

Error-handling antipatterns (BLOCKER class)

1. sp_send_dbmail inside CATCH — masks the real exception with a permission/configuration error when the executing login lacks EXECUTE on msdb.dbo.sp_send_dbmail. The real underlying error is silently lost.

   • Pattern: rg -n -B 20 'sp_send_dbmail' → check whether the surrounding context is a BEGIN CATCH.
   • Fix: Replace with ;THROW; to re-raise, or write the error info to a local log table. Never sp_send_dbmail from inside operational SPs.

2. Broken retry pattern — DECLARE @retry INT = N; exists, but no WHILE @retry loop wraps the TRY/CATCH. The retry variable is decremented in the CATCH but never read, so the SP gives up on the first deadlock instead of retrying.

   • Pattern: rg -n '@retry' → confirm there's a matching WHILE.*@retry somewhere in the same SP body.
   • Fix: Add the missing WHILE @retry > 0 BEGIN ... END around the TRY/CATCH, or remove the vestigial variable entirely.

3. Empty / swallowing CATCH blocks — BEGIN CATCH ... END CATCH with no THROW, no RAISERROR, and no INSERT INTO . Silent failure → silent data loss.

   • Pattern: rg -n -A 30 'BEGIN CATCH' → check each match for at least one of THROW, RAISERROR, or INSERT INTO.
   • Fix: End the CATCH with ;THROW; unless there's a deliberate reason to suppress (and document that reason).

4. BEGIN TRANSACTION without TRY/CATCH + XACT_STATE handling — an error mid-transaction leaves an open transaction on the connection.

   • Pattern: rg -n 'BEGIN TRAN' → confirm the same SP has BEGIN TRY and XACT_STATE() checks in CATCH.
   • Fix: Wrap in BEGIN TRY / BEGIN TRANSACTION ... COMMIT TRANSACTION / END TRY / BEGIN CATCH / IF XACT_STATE() = -1 ROLLBACK; IF XACT_STATE() = 1 COMMIT; ;THROW; / END CATCH.

5. Vestigial control-flow comments — -- end while loop with no WHILE keyword, -- retry on deadlock with no retry loop, etc. Strong signal that a refactor left dead code behind.

   • Pattern: rg -n -- '-- end (while|for|repeat)' → check for matching opening keyword.
   • Fix: Either restore the missing loop or delete the misleading comment.

Schema / performance antipatterns (BLOCKER for new tables, WARN otherwise)

1. New CREATE TABLE without a primary key, clustered index, or any index — heap tables will deadlock-and-table-scan once they grow. This is the exact pattern that caused real production deadlocks.

   • Pattern: rg -n -A 50 'CREATE TABLE' → confirm at least one of PRIMARY KEY, CLUSTERED INDEX, or CREATE INDEX exists on that table within the diff or in a sibling file.
   • Fix: Add PRIMARY KEY CLUSTERED on the natural ID column. If the table is append-mostly with no natural ID, add a clustered index on the column the populating SPs filter by in WHERE.

2. Parameter-to-column type-width mismatches — passing @x VARCHAR(50) into a column declared VARCHAR(3) causes silent truncation (or runtime error 8152 depending on ANSI_WARNINGS).

   • Pattern: cross-reference the SP's @param VARCHAR(N) declarations against the target table's column widths. Flag any narrowing.
   • Fix: Match widths between parameter and column, or add explicit LEFT(@x, 3) truncation at the boundary so it's intentional and visible.

3. Implicit type conversions in JOIN / WHERE — WHERE intCol = @varcharParam defeats indexes and produces table scans.

   • Pattern: rg -n -i 'WHERE\s+\w+\s*=\s*@\w+' → cross-check parameter type vs. column type.
   • Fix: Match the parameter type to the column type. If they're authoritatively different, cast the parameter, not the column (casting the column kills the index).

Security antipatterns (BLOCKER)

1. Dynamic SQL via string concatenation passed to EXEC() without sp_executesql @stmt, @params parameterization — SQL injection.

   • Pattern: rg -n 'EXEC\s*\(' → confirm any string-concat dynamic SQL nearby uses sp_executesql with parameters, not EXEC(@strSQL) with values inlined.
   • Fix: Switch to EXEC sp_executesql @stmt = @strSQL, @params = N'@p1 INT, @p2 VARCHAR(50)', @p1 = @value1, @p2 = @value2;.

2. Hardcoded environment-specific values — email addresses, server names, file paths, IP addresses, connection strings.

   • Pattern: rg -nE "'[\w.-]+@[\w.-]+\.\w+'|@server_name\s*=\s*'\w+'|\\\\\\\\[\\w.-]+\\\\" (emails, linked servers, UNC paths).
   • Fix: Move env-specific values into a configuration table or pass them as parameters from the application layer.

3. Cross-database references — msdb.dbo.*, master.dbo.*, linked server [srv].db.dbo.*. These require permissions that may not exist in all environments (the canonical example: a SP calling msdb.dbo.sp_send_dbmail from a login that lacks EXECUTE on it).

   • Pattern: rg -n 'msdb\.|master\.dbo\.|\[\w+\]\.\w+\.\w+\.' .
   • Fix: Move the cross-DB call out of operational SPs into infrastructure-owned code. If it must stay, document the required permission in a comment so deployments to new environments include the GRANT.

Correctness / data-safety antipatterns (BLOCKER)

1. UPDATE or DELETE without a WHERE clause — almost always a bug; will affect every row.

   • Pattern: rg -n -B 0 -A 20 'UPDATE\s+\w+' → confirm a WHERE clause is present and not commented out.
   • Pattern: rg -n -B 0 -A 10 'DELETE\s+FROM' → same.
   • Fix: Add the WHERE clause. If "every row" really is intended (TRUNCATE-style), use TRUNCATE TABLE and add a comment explaining why.

2. NOLOCK / READ UNCOMMITTED inside transactional write paths — WITH (NOLOCK) is fine for ad-hoc reporting reads, but in an UPDATE/INSERT/DELETE SP it can read uncommitted data and corrupt the write.

   • Pattern: rg -n -i 'NOLOCK|READ UNCOMMITTED' → check whether the same SP has INSERT, UPDATE, or DELETE against the same tables.
   • Fix: Remove the hint on tables being modified. Consider SNAPSHOT isolation if the goal is to avoid blocking.

3. TRUNCATE TABLE or DROP without IF EXISTS in deploy scripts that are supposed to be idempotent (re-runnable). Many repos use flat idempotent Deploy_*.sql files where re-runs must not fail on missing objects.

   • Pattern: rg -n -i 'DROP (TABLE|PROC|FUNCTION|VIEW)' → confirm IF EXISTS or OBJECT_ID(...) IS NOT NULL guard.
   • Fix: IF OBJECT_ID('dbo.X', 'U') IS NOT NULL DROP TABLE dbo.X; or DROP TABLE IF EXISTS dbo.X; (SQL 2016+).

Style / convention (WARN/INFO)

1. Missing SET NOCOUNT ON at the top of a new CREATE PROC — causes extra round-trips to the client and breaks some ORM drivers that don't handle row-count messages.

   • Pattern: rg -n -A 5 'CREATE PROC' → confirm SET NOCOUNT ON appears within the first ~10 lines of the procedure body.
   • Fix: Add SET NOCOUNT ON; as the first statement after AS BEGIN.

2. Cursors without READ_ONLY FORWARD_ONLY LOCAL — default cursors are slow and persist beyond the current batch.

   • Pattern: rg -n 'DECLARE\s+\w+\s+CURSOR\b' → confirm READ_ONLY FORWARD_ONLY LOCAL (or FAST_FORWARD) is specified.
   • Fix: DECLARE c CURSOR READ_ONLY FORWARD_ONLY LOCAL FOR SELECT ....

3. Missing GRANT EXECUTE at end of CREATE PROC — only flag when the rest of the repo has a consistent GRANT EXECUTE ON ... TO pattern at the end of every SP file. Detect the pattern by sampling a few neighboring .sql files; if every existing SP grants to the same role and this new SP doesn't, flag it.

   • Pattern: rg -n 'GRANT\s+EXECUTE' → confirm present if the repo convention requires it.
   • Fix: Append GRANT EXECUTE ON [dbo].[] TO [] GO matching the role the rest of the repo grants to.

Output format

# SQL review — uncommitted changes

**SQL files changed:**  (, )

---

## Verdict
**Ship / Fix blockers first**


---

## Blockers ()

### B1.  — `path/to/file.sql:`
**Evidence:** ``
**Why:** 
**Fix:** 

### B2. ...

## Warnings ()

### W1.  — `path/to/file.sql:`
**Evidence:** ``
**Why:** ...
**Fix:** ...

## Info ()
- `path:line` — 

---

## Summary
- BLOCKER: 
- WARN: 
- INFO: 

## Fixes I can apply

If you want, I can apply any of: B1, B2, W1. Which? (or "all", or "none")

End with the offer. Wait for the user's choice.

Examples

Example 1: New stored proc with mixed issues

User: "/sql-review"

Claude:

• Runs git diff --staged -- '*.sql' and git diff -- '*.sql' in parallel.
• Finds one new file Stored Procedures/dbo.usp_NewSave.sql.
• Spots:
  • B1 — BEGIN CATCH without ;THROW; (line 88) — swallowing.
  • B2 — calls EXEC msdb.dbo.sp_send_dbmail inside that CATCH (line 92) — masking risk.
  • W1 — missing SET NOCOUNT ON at line 6.
  • W2 — WITH (NOLOCK) on the table being UPDATEd (line 45).
  • I1 — missing GRANT EXECUTE at end of file (the repo's other SPs all end with it).
• Reports, then asks: "Want me to fix B1, B2, W1, W2, I1?"

Example 2: Adding a new table — the canonical incident pattern

User: "review the SQL diff before I push"

Claude:

• Spots Tables/dbo.NewAuditLog.sql (new file) — CREATE TABLE declared but no PRIMARY KEY, no CLUSTERED INDEX, no CREATE INDEX.
• Flags as B1 — "Heap table will table-scan on every read/UPDATE. Once the table grows past a few hundred thousand rows under concurrent writes, SQL Server's optimizer picks parallel plans and the workers deadlock on heap pages — a recurring production incident pattern."
• Fix: "Add PRIMARY KEY CLUSTERED (id) or a clustered index on the lookup column."
• Also flags the SP that populates the new table (B2 — implicit type conversion WHERE recordID = @recordID where the new table's recordID is INT but the param is declared VARCHAR).

Example 3: Modified existing SP — flag only new badness, not legacy

User: "lint the SQL — just the staged hunks"

Claude:

• The file usp_UpdateBigOldSP.sql is modified but huge. The user's diff added a 20-line block that does UPDATE dbo.Customers SET ... without a WHERE clause.
• Only flags the new block's UPDATE without WHERE as B1 — does NOT flag the legacy sp_send_dbmail call elsewhere in the file (which was already there before the user's edit).
• Notes in the report footer: "1 pre-existing antipattern observed in this file but outside the diff — flagging suppressed per scope. Full-file audit available on request."

Anti-patterns

• ❌ Trying to parse SQL with a full grammar — use ripgrep on the diff text. The skill is heuristic by design.
• ❌ Flagging every existing antipattern in a modified file. Stay scoped to the diff for modified files; full-file scan only for new files.
• ❌ Editing SQL during the review pass. Report first, always.
• ❌ Suggesting autofixes for BLOCKER items without asking. SQL deploys to production; user confirmation gates the change.
• ❌ Listing a nit when there's a BLOCKER next to it. Lead with severity.
• ❌ Hand-wavy findings without file:line.
• ❌ Reporting a raw ripgrep hit without reading the surrounding procedure. A pattern match is a candidate; the proc's full context sets the severity (see Pattern hit ≠ finding).
• ❌ Paraphrasing the offending SQL instead of quoting it verbatim. WITH (NOLOCK) vs READPAST, @retry vs @retryCount — the exact token is the finding.
• ❌ A BLOCKER with no one-sentence production-incident scenario. Can't name the incident? It's a WARN.
• ❌ Padding a clean diff with stretched findings. Zero findings is a valid report.
• ❌ Inventing antipatterns not in What to check. This is a fixed catalog — extending it is a write-a-skill change, not a per-run improvisation.
• ❌ Running on non-SQL files. The skill is .sql-scoped; mixed diffs route to code-review for the non-SQL parts.
• ✅ Diff-scoped scan for modified files, full scan for new files, findings categorized + cited + offered as fixes.

Notes

• The check catalog is intentionally finite — 17 checks chosen because each one maps to a real production incident class. Don't try to be a full SQL linter (e.g. SQLFluff or sqlcheck) — those exist and run from CI; this skill is the pre-commit human-pass complement focused on bug classes that linters miss.
• For repos that use flat idempotent Deploy_*.sql files (every deploy is a full re-run), check #14 (DROP / TRUNCATE without IF EXISTS) is critical — the deploy will fail on second run otherwise. For repos that use forward-only migrations, this check is lower priority.
• The "broken retry" pattern (check #2) is sneakier than it sounds: a DECLARE @retry INT = 5; followed by SET @retry = @retry - 1; in CATCH but no WHILE loop looks like deadlock handling. It isn't. Multiple SPs in real codebases have this bug from removed-loop refactors.
• If the user wants the broader cleanup (refactor every legacy SP in the repo with one of these issues), recommend opening a tracked task rather than doing it in the current review — these fixes ripple through deploy pipelines and need coordinated review.
• This skill composes downstream with code-review — on a mixed diff (.cs + .sql), run code-review for the application code and sql-review for the database changes.