Database Design & Architecture

SQL Query Sample Library & Template Builder

Explore a curated repository of production SQL query samples. Select from Common Table Expressions (CTEs), Window Functions, Multi-Table Joins, and Upsert statements across PostgreSQL, MySQL, SQL Server, and SQLite.

CTEs & Subqueries

Window Functions

Data Modification & Upsert

Basic Common Table Expression (CTE)

Isolate intermediate query results using the WITH clause to improve readability and query planner optimization.

Writing High-Performance SQL in Relational Databases

Writing optimal SQL queries requires structuring data access patterns to leverage indexes, minimizing table scans, and avoiding unnecessary nested subqueries in hot execution paths.

1. Window Functions vs Correlated Subqueries

When calculating aggregations across partitions (such as monthly department budgets or top-selling products per category), standard ANSI SQL Window Functions (like ROW_NUMBER() OVER (...) or SUM(amount) OVER (PARTITION BY ...)) outperform self-joins and subqueries by computing values in a single sequential scan.

2. Safe Upsert Patterns

Concurrent inserts can cause primary key collision exceptions. Using native dialect upsert semantics (such as PostgreSQL's ON CONFLICT (id) DO UPDATE or SQL Server's MERGE) guarantees atomicity inside a single ACID transaction.

Frequently Asked Questions

It provides developers, DBAs, and data analysts with curated, syntactically verified SQL query patterns for advanced database tasks including Recursive Common Table Expressions (CTEs), Window Analytics, complex multi-table joins, and safe upsert statements.

PostgreSQL and MySQL use LIMIT 20 OFFSET 40. SQL Server (T-SQL) requires standard ANSI OFFSET 40 ROWS FETCH NEXT 20 ROWS ONLY, which must be preceded by an ORDER BY clause.

Both assign ranking positions to rows within a partition. RANK() skips rank numbers after a tie (e.g. 1, 2, 2, 4), while DENSE_RANK() always produces contiguous sequence numbers without gaps (e.g. 1, 2, 2, 3).

PostgreSQL and SQLite use INSERT INTO ... ON CONFLICT (col) DO UPDATE SET. MySQL uses INSERT INTO ... ON DUPLICATE KEY UPDATE. SQL Server and Oracle utilize the MERGE INTO statement.