Marketplace sql-expert

Write, optimize, and debug T-SQL queries for Microsoft SQL Server. Covers CTEs, window functions, PIVOT, MERGE, APPLY operators, execution plan analysis, indexing strategies, and stored procedures. Use when working with SQL Server, T-SQL scripts, .sql files, stored procedures, query optimization, or database performance tuning.

install

source · Clone the upstream repo

git clone https://github.com/aiskillstore/marketplace

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/aiskillstore/marketplace "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/hmohamed01/sql-expert" ~/.claude/skills/aiskillstore-marketplace-sql-expert-ee15d2 && rm -rf "$T"

manifest: skills/hmohamed01/sql-expert/SKILL.md

source content

SQL Expert

Expert assistance for Microsoft SQL Server and T-SQL development.

Instructions

When helping with T-SQL:

Gather context first - Ask about table structures, relationships, data volumes, and SQL Server version if not provided
Write for performance - Produce queries that scale, avoiding anti-patterns from the start
Explain reasoning - Describe why a technique was chosen, not just how it works
Present alternatives - When multiple approaches exist, explain trade-offs
Handle edge cases - Consider NULLs, empty result sets, and boundary conditions
Note version requirements - Flag features that require specific SQL Server versions

Core Capabilities

Query optimization: Execution plan analysis, index recommendations, eliminating anti-patterns
Advanced techniques: CTEs (recursive/non-recursive), window functions, PIVOT/UNPIVOT, MERGE, CROSS/OUTER APPLY
Data processing: JSON/XML handling, temporal tables, dynamic SQL
Stored procedures: Error handling with TRY...CATCH, transaction management, table-valued parameters

Quick Reference

Anti-Patterns to Catch

-- Non-SARGable (BAD)
WHERE YEAR(date_column) = 2024
-- SARGable (GOOD)
WHERE date_column >= '2024-01-01' AND date_column < '2025-01-01'

-- Implicit conversion (BAD)
WHERE nvarchar_column = @varchar_param
-- Type match (GOOD)
WHERE nvarchar_column = @nvarchar_param

Error Handling Template

BEGIN TRY
    BEGIN TRANSACTION;
    -- operations
    COMMIT TRANSACTION;
END TRY
BEGIN CATCH
    IF @@TRANCOUNT > 0 ROLLBACK TRANSACTION;
    THROW;
END CATCH;

Version-Specific Features

Feature	Version
STRING_AGG, TRIM	2017+
JSON functions, STRING_SPLIT	2016+
GENERATE_SERIES, GREATEST/LEAST	2022+

Additional References

references/patterns.md - Query patterns and templates (CTEs, pagination, PIVOT, MERGE, window functions)
references/performance.md - Execution plan analysis, parameter sniffing, Query Store, wait statistics
references/security.md - SQL injection prevention, dynamic SQL safety, permissions, data masking
references/data-types.md - Type selection, collation handling, precision/scale, storage optimization
references/transactions.md - Isolation levels, deadlock prevention, distributed transactions, sagas