SQL Tutorials: Queries, Joins, and Safe Data Changes
Learn practical SQL basics with examples for filtering, sorting, grouping, joins, NULL values, and safe data changes.
SQL guides
SQL SELECT and WHERE: Retrieve the Rows You NeedLearn to select specific SQL columns and filter rows with WHERE conditions and safe examples.
SQL ORDER BY: Sort Query ResultsSort SQL query output with ORDER BY, multiple sort keys, and explicit ascending or descending order.
SQL GROUP BY and COUNT for Simple ReportsGroup SQL rows by a category and count records with GROUP BY, COUNT, and HAVING.
SQL JOINs for Beginners: Match Rows Across TablesUnderstand INNER JOIN and LEFT JOIN with keys, aliases, and checks for duplicated results.
SQL INSERT, UPDATE, and DELETE: Change Data CarefullyLearn the basic shape of SQL INSERT, UPDATE, and DELETE statements and how to review affected rows safely.
How SQL NULL Works in Filters and ComparisonsUnderstand why SQL NULL is not zero or an empty string and how to test for missing values correctly.
SQL CREATE TABLE and Primary Keys: A Beginner's GuideCreate a simple SQL table with named columns, data types, and a primary key while considering uniqueness and nullability.
SQL FunctionsAggregate, string, date and conditional functions.
SQL Interview QuestionsCommon questions with clear answers.