title: “String Functions (UPPER, LOWER)” part: 1 topic_number: 20 slug: “string-functions-upper-lower” difficulty: “Beginner” prerequisites: “select-from-where” — String Functions (UPPER, LOWER) ...

title: “NULL Handling (IS NULL / IS NOT NULL)” part: 1 topic_number: 19 slug: “null-handling” difficulty: “Beginner” prerequisites: “select-from-where” — NULL Handling What Is It? NULL represent...

title: “DISTINCT” part: 1 topic_number: 18 slug: “distinct” difficulty: “Beginner” prerequisites: “select-from-where” — DISTINCT What Is It? DISTINCT eliminates duplicate rows from your query re...

title: “LEFT JOIN” part: 1 topic_number: 16 slug: “left-join” difficulty: “Beginner” prerequisites: “inner-join” — LEFT JOIN What Is It? LEFT JOIN returns ALL rows from the left table, and match...

title: “INNER JOIN” part: 1 topic_number: 15 slug: “inner-join” difficulty: “Beginner” prerequisites: “primary-foreign-keys, select-from-where” — INNER JOIN What Is It? INNER JOIN combines rows ...

title: “Primary Key and Foreign Key Concepts” part: 1 topic_number: 14 slug: “primary-foreign-keys” difficulty: “Beginner” prerequisites: “create-table” — Primary Key and Foreign Key Concepts Wha...

title: “HAVING vs WHERE” part: 1 topic_number: 13 slug: “having-vs-where” difficulty: “Beginner” prerequisites: “group-by, aggregate-functions” — HAVING vs WHERE What Is It? WHERE filters rows B...

title: “GROUP BY” part: 1 topic_number: 12 slug: “group-by” difficulty: “Beginner” prerequisites: “aggregate-functions” — GROUP BY What Is It? GROUP BY splits your data into categories, then cal...

title: “Aggregate Functions (COUNT, SUM, AVG, MIN, MAX)” part: 1 topic_number: 11 slug: “aggregate-functions” difficulty: “Beginner” prerequisites: “select-from-where” — Aggregate Functions What ...

title: “LIMIT” part: 1 topic_number: 10 slug: “limit” difficulty: “Beginner” prerequisites: “order-by” — LIMIT What Is It? LIMIT restricts the number of rows returned by a query. It’s perfect fo...