SQL Query Optimizer
Online SQL query optimizer with multi-database performance analysis, index suggestions, and risk hints for early slow-query detection
Database Setup
Database Tip:
SQL Query
Only SELECT query analysis is supported for now. Please check SQL syntax.
Optimization Scenarios
Performance Analysis
Needs Optimization
Query Cost
0
Estimated Rows
0
Index Usage
Query ComplexitySimple
Estimated Time0ms
Optimization Suggestions
0 suggestionsIndex Suggestions
Ready. Enter SQL to analyze performance in real time.
Guide
SQL Query Optimizer helps evaluate potential performance risks in SELECT queries and outputs actionable rewrite and indexing suggestions so you can catch slow-query issues earlier in development.
Key Features
- Supports multiple database engines and table-size estimation for adaptive analysis.
- Supports real-time SQL parsing, formatting, and performance score display.
- Provides high/medium/low-priority suggestions with rewrite snippets.
- Generates index recommendations from WHERE and ORDER BY patterns.
How To Use
- Select database type and table size, then set custom rows if needed.
- Enter SQL or load a scenario example to view analysis output.
- Resolve high-priority issues first, then tune medium and low priorities.
- Validate final tuning with EXPLAIN and real workload checks.
Optimization Rules
Basic
- Avoid SELECT * and fetch only required columns.
- Add WHERE filters for large-table queries whenever possible.
- Create indexes for high-frequency filtering columns.
- Use LIMIT for API-facing query result control.
Performance
- Avoid leading-wildcard LIKE '%keyword' to keep index usability.
- When JOIN count is high, consider query decomposition.
- Use EXISTS/NOT EXISTS for heavy IN/NOT IN cases.
- Pair ORDER BY with indexed columns and LIMIT when possible.
Advanced
- Reduce functions in WHERE predicates to avoid index loss.
- Use covering indexes for high-frequency read paths.
- Tune per SQL dialect and optimizer behavior.
- Validate with EXPLAIN and slow-query logs before release.
FAQ
- Why SELECT only: this version focuses on query-read performance and lower false positives.
- Are suggestions always correct: no, they are rule-based and should be validated with real data.
- Why score changes for same SQL: table scale and selected database affect estimation.
- Will SQL be uploaded: no, all processing happens locally in your browser.
Privacy
This tool does not upload your SQL. Parsing, scoring, and suggestion generation all run locally in your browser.