Tag: Learn SQL

SQL aliases tutorial: rename columns and tables with AS, name calculated columns, shorten join queries with table aliases, and where aliases can be used.

SQL BETWEEN operator tutorial: filter numbers, dates and text within an inclusive range, NOT BETWEEN, the end-of-day date trap, and examples with output.

SQL IN operator tutorial: match a column against a list of values, NOT IN, IN with a subquery, IN vs OR, the NULL trap with NOT IN, and examples with output.

SQL wildcards explained: the % and _ characters, SQL Server [ ] ranges, escaping literal % or _, worked examples with results and common mistakes.

SQL LIKE operator tutorial: match text patterns with % and _ wildcards, NOT LIKE, case sensitivity by database, and worked examples with output.

SQL COUNT, AVG and SUM tutorial: count rows, total and average a column, COUNT(*) vs COUNT(column), how NULLs are ignored, and examples with output.

SQL MIN and MAX tutorial: find the lowest and highest values in a column, use them with WHERE and GROUP BY, get the full row with a subquery, plus NULL rules.

SQL TOP, LIMIT and FETCH FIRST limit the rows a query returns. Syntax for MySQL, SQL Server, PostgreSQL and SQLite, OFFSET pagination and top-N examples.

SQL DELETE tutorial: remove rows with WHERE, delete using a subquery or join, DELETE vs TRUNCATE vs DROP, and how to avoid deleting everything.

SQL UPDATE tutorial: change one or many columns with SET and WHERE, update using calculations, update from another table with a join, and stay safe.