SQL Query Validator

Runs in browser Database

A dialect-aware structural validator for SQL: keyword order, clause structure, balanced parentheses and quotes, missing WHERE in UPDATE/DELETE, SELECT * warnings and injection-prone concatenation.

Privacy: This tool runs entirely in your browser. Your input never leaves your device.

What is SQL, and why does the dialect matter?

SQL is the query language of relational databases, standardised in outline but implemented with dialect differences — quoting rules, functions, LIMIT versus TOP, date literals — by PostgreSQL, MySQL, SQLite, SQL Server and Oracle. A formatter normalises keywords, indentation and line breaks so a long query can be read and reviewed; a validator parses the statement to find syntax errors before it reaches the database.

Security note: Generated INSERT or IN-clause statements are for fixtures and migrations. In application code, values must go through parameterised queries — building SQL from user input by string concatenation is how SQL injection happens.

How to use SQL Query Validator

  1. Paste one or more statements separated by semicolons.
  2. Pick the dialect.
  3. Review the issue table — errors block execution, warnings are risky patterns, and INFO rows (counted as Hints) are style advice.

SQL Query Validator features

  • Lexical checks: unterminated strings, comments and quoted identifiers
  • Balanced parentheses and CASE … END pairs, trailing commas, dangling operators
  • Clause order for SELECT (FROM → WHERE → GROUP BY → HAVING → WINDOW → ORDER BY → LIMIT / OFFSET / FETCH)
  • Safety warnings: UPDATE/DELETE without WHERE, JOIN without ON, "= NULL"
  • INSERT column/value count mismatches
  • Injection smells: string concatenation with variables, OR 1=1 tautologies
  • Dialect hints (LIMIT vs TOP, backticks vs brackets)

SQL Query Validator example

Catch a clause-order mistake

Input:

SELECT * FROM users ORDER BY id WHERE active = 1

Output:

ERROR line 1: WHERE appears after ORDER BY; the expected order is SELECT → FROM → WHERE → GROUP BY → HAVING → WINDOW → ORDER BY → LIMIT.
INFO line 1: SELECT * returns every column.

Frequently asked questions about SQL Query Validator

Does it connect to my database?

No. Validation is purely structural and runs in your browser: it checks quotes, parentheses, clause order and dangerous patterns, but it cannot know whether tables and columns exist.

What kinds of problems does it detect?

Unterminated strings and comments, unbalanced parentheses, clauses in the wrong order (e.g. WHERE after ORDER BY), trailing commas, dangling operators, INSERT column/value count mismatches, missing WHERE on UPDATE/DELETE, JOINs without ON, "= NULL" comparisons and dialect-specific syntax such as LIMIT in SQL Server.

What is the injection warning?

It flags string literals concatenated with variables ('…' + @user), tautologies such as OR 1=1 and payload-like literals. Use bound parameters instead of building SQL from strings.

Can I validate multiple statements?

Yes. Statements are split on semicolons and each is reported with its own index, type and issues.

Technical notes

Because the validator does not know your schema, it cannot report unknown tables or columns. It is a fast first line of defence for hand-written queries, code review and CI checks on migration scripts.

References

  • PostgreSQL Documentation: SQL SyntaxThe PostgreSQL Global Development GroupLexical structure of SQL in PostgreSQL: identifiers, quoting, string constants and escaping.
  • SQL As Understood By SQLiteSQLiteThe SQL grammar accepted by SQLite, statement by statement, with railroad diagrams.
  • SQL InjectionOWASP FoundationHow SQL injection works and why parameterised queries, not string building, are the defence.