Question 1

What does the SQL checker look for?

Accepted Answer

The checker scans for common issues including SELECT * usage (performance warning), missing semicolons, unbalanced parentheses, common typos such as FORM instead of FROM, SELET instead of SELECT, and WHER instead of WHERE, LIKE '%value%' patterns that skip indexes, and DELETE or UPDATE statements without a WHERE clause.

Question 2

What does the NoSQL / MongoDB checker look for?

Accepted Answer

For MongoDB-style queries the checker validates JSON structure, warns about $where operator usage which can be a security risk, flags deeply nested queries beyond 3 levels as a performance concern, and notes missing index hints for potentially large collection operations.

Question 3

Does the tool actually execute my query?

Accepted Answer

No. The checker is entirely static — it uses regex patterns and keyword analysis to detect issues without connecting to any database. Your query text never leaves your browser.

Question 4

Can I use the auto-check feature?

Accepted Answer

Yes. The checker automatically re-runs 800 ms after you stop typing, so you get instant feedback without clicking the Check button. You can also click the button manually at any time.

Question 5

Is this tool a replacement for a proper SQL linter?

Accepted Answer

It is a quick sanity-check for common mistakes, not a full SQL parser. It does not understand complex subqueries, CTEs, or dialect-specific syntax. For production use, complement this tool with your database's own EXPLAIN plan.

SQL / NoSQL Checker

Frequently Asked Questions