CodeWithSQL Blog: Latest SQL Tips and Tutorials

SQL aggregate functions explained: COUNT, SUM, AVG, MIN, MAX and GROUP_CONCAT, NULL handling, GROUP BY and HAVING, and conditional aggregation with CASE.

SQL subqueries vs JOINs: the types of subqueries, correlated vs non-correlated, EXISTS vs IN vs JOIN, and when each is clearer or faster, with examples.

INNER JOIN vs LEFT JOIN vs RIGHT JOIN vs FULL JOIN: what rows each keeps, a side-by-side comparison, examples with results, and which join to pick when.

ORDER BY, GROUP BY and HAVING explained: how to sort, group and filter groups in SQL, the difference between WHERE and HAVING, and the logical processing order.

The SQL WHERE clause explained with real examples: comparison and logical operators, IN, BETWEEN, LIKE and IS NULL, WHERE vs HAVING, and sargable filters.

The SQL SELECT statement explained with 25 examples: columns, DISTINCT, WHERE, ORDER BY, GROUP BY, HAVING, joins, subqueries and a window function, with results.

How to write better SQL queries: name columns, write sargable predicates, use CTEs and joins well, format for readability, handle NULLs, and read the query plan.

SQL transactions explained: COMMIT, ROLLBACK and SAVEPOINT, the four ACID properties, isolation levels and the anomalies they prevent, with clear examples.

SQL indexes explained for beginners: what an index is, how it speeds up reads, clustered vs non-clustered, which columns to index, and the read and write trade-off.

SQL views explained: what a view is, how to create and query one, updatable views, materialized views and refresh, and when views help or hurt performance.