SQL Index Advisor - Suggest Indexes for Performance

Analyze your SQL queries and get suggestions for creating database indexes. This advisor identifies slow columns and recommends indexes to speed up SELECT, JOIN, and WHERE clauses.

SQL Index Advisor

Analyze queries and get index recommendations for better performance

SQL Query

Table Schema (Optional)

Index Recommendations

No suggestions yet. Enter a SQL query to analyze.

Index Types

BTREE: Default index type, good for equality and range queries
HASH: Fast for exact match lookups, not suitable for range queries
FULLTEXT: For text search and LIKE pattern matching
SPATIAL: For geographic/spatial data types

Index recommendations are based on query analysis. Always test indexes in your environment and consider existing indexes, table size, and write patterns before creating new indexes.

How It Works

This SQL index advisor analyzes your SELECT queries and recommends database indexes that could improve query performance by reducing scan times and speeding up lookups.

The analysis process:

Query parsing: The tool examines your SQL to identify tables, columns used in WHERE clauses, JOIN conditions, and ORDER BY statements.
Access pattern detection: Columns frequently used for filtering, joining, or sorting are flagged as index candidates.
Index recommendation: Based on query patterns, the tool suggests single-column or composite indexes that would benefit performance.
CREATE INDEX generation: Ready-to-execute CREATE INDEX statements are produced for your specific database dialect.

Proper indexing is the single most effective way to improve query performance. This tool helps identify which indexes will have the biggest impact on your specific queries.

When You'd Actually Use This

Slow Query Optimization

Analyze queries that are taking too long and get specific index recommendations to speed them up.

New Feature Development

Before deploying new queries, check what indexes they would benefit from and create them proactively.

Database Performance Audits

Review all application queries to identify missing indexes across your entire codebase.

Learning Database Optimization

Understand which query patterns benefit from indexes and how composite indexes work.

Migration Planning

When moving to a new database, analyze queries to design an optimal indexing strategy from the start.

Index Cleanup

Identify which indexes are actually useful vs. which ones are never used by your queries.

What to Know Before Using

Indexes speed up reads but slow down writes

Every INSERT, UPDATE, DELETE must also update indexes. Don't over-index tables with heavy write loads.

Composite index column order matters

For indexes on multiple columns, the leftmost columns are most selective. Order columns by filter frequency and selectivity.

Existing indexes may already cover your query

Check what indexes already exist before adding new ones. Some queries can use existing indexes in unexpected ways.

Small tables don't need indexes

Tables with fewer than 1000 rows often scan faster than using an index. Indexing benefits grow with table size.

Query optimizer may not use your index

The database optimizer decides whether to use an index based on statistics. Outdated statistics can lead to poor index usage.

Common Questions

What's the difference between a clustered and non-clustered index?

Clustered indexes determine the physical order of data in a table (one per table). Non-clustered indexes are separate structures pointing to data rows. Primary keys are often clustered.

How many indexes should a table have?

There's no fixed limit, but 5-10 indexes per table is common. More indexes increase write overhead. Each index should serve a clear query pattern.

When should I use a composite index?

Use composite indexes when queries frequently filter on multiple columns together. The index should match the most common column combinations in your WHERE clauses.

Do foreign keys need indexes?

Yes, foreign key columns should typically be indexed. This speeds up JOINs and prevents lock escalation during parent table updates/deletes.

What's a covering index?

A covering index includes all columns needed by a query, so the database doesn't need to look up the actual table rows. This is very fast but requires careful design.

How do I know if an index is being used?

Use EXPLAIN or execution plan tools to see if your query uses the index. Database statistics views (like sys.dm_db_index_usage_stats in SQL Server) show index usage over time.

Should I index boolean or low-cardinality columns?

Generally no. Columns with few distinct values (gender, status flags) rarely benefit from indexing unless combined with other columns in a composite index.

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SQL Index Advisor - Suggest Indexes for Performance