# SQL Syntax Validator MCP

> SQL Syntax Validator immediately audits any SQL query for structural errors before it hits your database. It uses Abstract Syntax Tree parsing to find missing commas, misplaced parentheses, or invalid join structures. This prevents runtime crashes and deadlocks caused by flawed code generated by AI agents.

## Overview
- **Category:** developer-tools
- **Price:** Free
- **Tags:** sql-validation, syntax-checking, ast-parsing, query-optimization, error-prevention

## Description

AI agents are great at drafting complex queries, but they're terrible reviewers. They often leave behind subtle syntax mistakes—a forgotten comma in a massive JOIN statement, an incorrectly closed parenthesis, or using duplicate column aliases. Running these flawed queries directly against production data is a recipe for bottlenecks and deadlocks.

This MCP solves that problem by validating the query structure locally before execution. It doesn't need to talk to your database; it just parses the code itself. By supporting major dialects like PostgreSQL, MySQL, MariaDB, and BigQuery, you can trust that your generated SQL is syntactically sound across different environments.

When you connect this MCP through Vinkius, you gain an immediate safety check for any AI client or agent. You just pass the raw query string, and it tells you exactly where the syntax breaks down, pinpointing the error location before you even think about running it.

## Tools

### validate_sql
Pass a raw SQL query string and an optional dialect to check for syntax errors offline, preventing runtime database crashes.

## Prompt Examples

**Prompt:** 
```
Validate this PostgreSQL query before execution: `SELECT id, name FROM users WHERE email = 'test@example.com' ORDER BY created_at DESC;`
```

**Response:** 
```
✅ **Valid SQL Query:** {"valid": true, "database": "postgresql", "type": "select"}
```

**Prompt:** 
```
Check if this MySQL query is syntactically sound: `SELECT * FROM orders WHERE amount > 100 AND GROUP BY user_id`
```

**Response:** 
```
❌ **Syntax Error:** Expected end of input, found 'GROUP' at line 1, column 47.
```

**Prompt:** 
```
Audit this complex BigQuery join.
```

**Response:** 
```
✅ **Valid SQL Query:** Checked AST correctly.
```

## Capabilities

### Audit Query Structure
The MCP checks a raw SQL string against established grammar rules to confirm its structural integrity.

### Pinpoint Syntax Errors
It reports the exact location (line and column) of any syntax mistake in the query, saving debugging time.

### Support Multiple Dialects
The validator accepts different SQL dialects, including MySQL, PostgreSQL, MariaDB, and BigQuery, making it universal for your stack.

## Use Cases

### Refining an Agent-Generated SELECT Query
A data analyst asks their agent to pull user metrics across three tables. The agent drafts a huge query, but misses a comma in the WHERE clause. Instead of running it and getting a vague 'syntax error,' they feed the draft into this MCP's `validate_sql` tool. It immediately flags the missing comma, letting them fix the query before any damage is done.

### Switching Database Backends
A backend developer wrote a complex reporting query for their PostgreSQL staging environment. Now they need to port it to MariaDB. They run the same SQL through this MCP, specifying 'mariadb' as the dialect. The validator catches syntax differences unique to MariaDB that would have failed otherwise.

### Auditing Multi-Dialect Joins
A team is building a universal service layer using AI agents. They need one query structure that works across both MySQL and BigQuery. They use the MCP to test the same core logic against both dialects, ensuring compatibility for all client environments.

### Handling Complex UNION Statements
A data engineer needs to combine results from multiple sources using a complex UNION query structure. Before committing the code, they use this MCP's `validate_sql` function to audit the entire block, confirming that all column types and structures are consistent across every SELECT clause.

## Benefits

- Prevents deadlocks and bottlenecks. By using the validator, you confirm syntax integrity before execution, stopping database crashes caused by malformed AI-generated code.
- Supports major dialects out of the box. Whether you're working with PostgreSQL, MySQL, or BigQuery, this MCP validates against the correct grammar rules for your environment.
- Pinpoints errors instantly. Instead of getting a vague 'query failed,' you get precise feedback on the line and column where the syntax broke down.
- Saves time during development. You don't have to run every draft query through a local sandbox just to check commas or parentheses; this MCP handles it upfront.
- Reduces agent risk. When using AI agents, this validator acts as a mandatory safety layer, ensuring that complex queries are structurally sound before they reach the final execution stage.

## How It Works

The bottom line is you get immediate, non-destructive feedback on your SQL code's structure.

1. You provide the MCP with the raw SQL query string and specify the target database dialect (e.g., 'postgresql').
2. The underlying engine processes the code using Abstract Syntax Tree parsing, checking it against grammar rules without connecting to a live database.
3. The system returns a clear status: either confirmation that the query is valid or a detailed report pointing out specific syntax errors.

## Frequently Asked Questions

**Does SQL Syntax Validator handle all major database dialects?**
Yes, it supports MySQL, PostgreSQL, MariaDB, BigQuery, and others. You simply specify the dialect you are targeting when running the validation check.

**Can I use validate_sql on incomplete queries?**
Absolutely. The tool doesn't require a runnable query; it just needs enough syntax to determine if an error exists, making it perfect for auditing drafts.

**Is this MCP faster than running the query live?**
Yes, because it only performs local Abstract Syntax Tree parsing. It never connects to your actual database, so validation is extremely fast and resource-light.

**What kind of errors can SQL Syntax Validator prevent?**
It prevents structural issues like unmatched parentheses, missing commas in JOIN clauses, or using keywords that are invalid for the specified dialect.

**Does validate_sql check my data integrity?**
No. This MCP is strictly a syntax validator. It checks if the *grammar* of the query is correct; it doesn't verify if the columns or tables actually exist in your database.