Recent Posts
MariaDB Tutorial / Save Reusable Query Definitions with VIEW
Create an INVOKER view for paid-order totals, inspect its definition and observe transaction changes. Review security, updateability, dependencies and the difference between a view and stored result data.
MariaDB Tutorial / Calculate Running Totals and Compare Rows with LAG and LEAD
Calculate running totals, LAG and LEAD, then compare ROWS and RANGE with tied timestamps. Verify how filtering before or after accumulation changes a period report.
MariaDB Tutorial / Compare ROW_NUMBER, RANK, and DENSE_RANK
Compare ROW_NUMBER, RANK and DENSE_RANK on customer totals, then run regional rankings and an outer top-N filter. Check how a row limit differs from retaining tied ranks.
MariaDB Tutorial / Break Queries into Named Steps with WITH and CTEs
Build a readable multi-step query with WITH, verify paid orders and per-order totals independently, and understand CTE scope, naming and execution-plan limitations.
MariaDB Tutorial / Combine Query Results with UNION and UNION ALL
Stack compatible customer-query results, compare UNION with UNION ALL and observe how source labels change duplicate detection. Check column meaning, result types and ordering scope.
MariaDB Tutorial / Use Subqueries, EXISTS, and NOT EXISTS
Choose scalar and existence subqueries according to the result needed. Compare paid-order customers and absent-order customers, inspect correlation keys and avoid NULL-related exclusion assumptions.
MariaDB Tutorial / Avoid Duplicate Totals When Joining Multiple Tables
Trace row multiplication across customer, order, item and product joins. Reconcile correct goods and shipping totals, understand DISTINCT pitfalls and preaggregate details at the order grain.
MariaDB Tutorial / Keep Unmatched Rows with LEFT JOIN
Retain all customers with LEFT JOIN, distinguish ON and WHERE filters, count actual right-side matches and compare no-order customers with customers lacking paid orders.
MariaDB Tutorial / Read Related Rows with INNER JOIN
Join customer names to orders with explicit relationship keys, interpret repeated customers correctly and compare filtered INNER JOIN results with an unrestricted Cartesian product.
MariaDB Tutorial / Design Table Relationships with Keys and Foreign Keys
Build and inspect customer, product, order and item tables with foreign keys. Verify one-to-many links, reject missing parents and choose deliberate deletion and historical-price policies.