Every post tagged tutorials on the DbSchema blog.
Learn the SQL wildcard characters from short examples with their results: % and _, SQL Server's [ ] and [^ ], ESCAPE for a literal % or _, and what MySQL, PostgreSQL and SQLite use instead.
Learn SQL aggregate functions with COUNT, SUM, AVG, MIN, MAX, GROUP BY, HAVING, and ROLLUP examples. Build reporting queries faster in DbSchema.
Learn the SQL LIKE operator from short examples with their results: % and _, NOT LIKE and NULL, ESCAPE, ILIKE and case, several patterns, and index use.
Learn SQL HAVING with GROUP BY from short examples with their results: COUNT, AND, COUNT DISTINCT, HAVING without GROUP BY, HAVING vs WHERE, and the errors each engine raises.
ANY is true when one row of a subquery matches, ALL only when every row does. Short examples with their results, IN and NOT IN, NULLs and empty subqueries.
SQL aliases explained: rename columns and tables with AS, quote aliases with spaces, and see where an alias may be referenced in WHERE, GROUP BY, HAVING and ORDER BY.
SQL SELECT INTO creates a new table from a query result. Short examples with their results: a full copy, columns, WHERE, an empty copy, JOIN, and CREATE TABLE AS on MySQL, Oracle and SQLite.
Learn the SQL DELETE statement from short examples with their results: WHERE, SELECT before DELETE, subqueries and joins, ROLLBACK, RETURNING, and DELETE vs TRUNCATE vs DROP.
Learn the SQL UPDATE statement from short examples with their results: WHERE, several columns, expressions, transactions, subqueries and UPDATE with JOIN in PostgreSQL, MySQL, SQLite and SQL Server.
Learn SQL MIN() and MAX() from short examples with their results: NULL values, dates and text, GROUP BY, HAVING, the row that holds the value, and OVER.
SQL tables on one three-row table: CREATE TABLE, data types, the primary key, CREATE TABLE AS, ALTER TABLE ADD, MODIFY and DROP COLUMN, TRUNCATE and DROP TABLE.
SQL ORDER BY on one five-row table: ASC and DESC, multiple columns, aliases, GROUP BY, CASE, LIMIT pages, NULLS FIRST and NULLS LAST, and ties.
Learn how SQL NULL values behave in WHERE, COALESCE, NULLIF, COUNT, AVG, ORDER BY, GROUP BY, joins, NOT IN and UNIQUE, from short queries and their results.
Learn SQL INSERT INTO SELECT from short examples with their results: the column list, constants, JOIN, NOT EXISTS, LIMIT and TOP, SELECT INTO, and the errors to expect.
Learn SQL joins from short examples with their results: INNER, LEFT, RIGHT, FULL, CROSS and SELF JOIN, a diagram of the rows each one returns, and the mistakes that drop or repeat rows.
Learn SQL COUNT, SUM and AVG from short examples with their results: COUNT(*) and COUNT(column), DISTINCT, NULL values, GROUP BY, HAVING and empty results.
Learn what a foreign key is from short examples with their results: FOREIGN KEY and REFERENCES, NULL, ADD and DROP CONSTRAINT, ON DELETE CASCADE and self-referencing keys.
Learn what a primary key in SQL is from short examples with their errors: PRIMARY KEY, composite keys, ALTER TABLE, foreign keys, UNIQUE, AUTO_INCREMENT and IDENTITY, in PostgreSQL, MySQL and SQLite.
Learn SQL AND, OR and NOT from short examples with their results: what each operator keeps, why AND binds before OR, and why NOT drops rows with NULL.
SQL TOP, LIMIT, FETCH FIRST and ROWNUM on one six-row table: the syntax for each engine, OFFSET pages, WITH TIES, PERCENT, and the mistakes that return the wrong rows.
Learn about a common SQL pattern used to find rows in one table that have no matching rows in another. And some related counting problems.
How SQL statements are structured, a runnable example per command family, where engine syntax differs, and how to read a syntax error.
SQL INTERSECT on three small tables: the rules, duplicates and INTERSECT ALL, NULLs, INTERSECT vs INNER JOIN, operator order, and support in PostgreSQL, MySQL, SQLite and more.
Learn the SQL SELECT statement with syntax, WHERE, DISTINCT, JOINs, GROUP BY, ORDER BY, subqueries, and FAQs. Build queries visually in DbSchema.
SQL BETWEEN and NOT BETWEEN on numbers, dates, times and text, run on PostgreSQL, MySQL and SQLite: inclusive bounds, reversed bounds, NULLs and the timestamp upper bound.
SQL UNION and UNION ALL on two small tables: the column rules, which rows count as duplicates, ORDER BY and LIMIT, totals, and the errors PostgreSQL, MySQL and SQLite give.
How SQL EXISTS and NOT EXISTS test a subquery for rows, run on PostgreSQL, MySQL and SQLite: correlation, the NOT IN NULL trap, EXISTS against a join, and EXISTS in a DELETE.
How SQL IN and NOT IN filter rows with a value list or a subquery, why a NULL makes NOT IN return nothing, and the mistakes each engine reports.
SQL INSERT INTO syntax with one row, several rows, defaults and INSERT INTO SELECT, plus the errors PostgreSQL, MySQL and SQLite return when an insert fails.
Learn how to use the SQL WHERE clause with comparison, range, list and pattern operators, NULL, AND/OR precedence, and UPDATE or DELETE, with every result shown.
SQL SELECT DISTINCT with single and multi-column examples, how NULL is handled, the ORDER BY error, COUNT(DISTINCT) on two columns, and DISTINCT vs GROUP BY.
Learn SQL NULL-handling functions like IFNULL, ISNULL, COALESCE, and NVL, with examples, pitfalls, and practice exercises.
What the SQL CASE expression is, simple vs searched syntax, and examples in SELECT, ORDER BY, GROUP BY, UPDATE, INSERT, DELETE, and aggregate queries.
Learn SQL basics and database fundamentals with real-world examples, core concepts, and practical next steps.
Learn SQL GROUP BY with single and multi-column examples, HAVING, JOINs, aggregations, and common mistakes.
Learn SQL GROUP BY with clear examples for COUNT, SUM, AVG, HAVING, and JOIN-based reporting queries.
Create custom data types in DbSchema’s Logical Design to standardize columns; on deployment they convert to native DBMS types like VARCHAR.
