SQL SELF JOIN
A SELF JOIN is a regular JOIN where a table is joined with itself to compare rows within the same table. It’s commonly used…
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SQL FULL JOIN
FULL JOIN (or FULL OUTER JOIN) returns all rows from both tables. If there’s no match, unmatched columns return NULL. ✅ Combines the effects…
SQL RIGHT JOIN
RIGHT JOIN returns all rows from the right table, and matched rows from the left. If no match exists, left-side columns return NULL. 🔹…
SQL LEFT JOIN
LEFT JOIN returns all rows from the left table, and matched rows from the right. If there’s no match, right-side columns return NULL. 🔹…
SQL INNER JOIN
INNER JOIN combines rows from two or more tables only when matching values exist in both. 🔹 Basic Syntax 🔹 Example: Employees and Departments…
SQL CASE
CASE lets you add if-else logic inside SQL statements. It’s great for transforming data or creating new categorized columns. 🔹 Basic Syntax (Simple CASE)…
SQL HAVING
HAVING lets you filter grouped results after using GROUP BY. Think of it as a WHERE for aggregated data. 🔹 Basic Syntax 🔹 Example:…
SQL GROUP BY
GROUP BY is used to group rows that share the same values in specified columns and apply aggregate functions to each group. 🔹 Basic…
SQL COUNT / SUM / AVG / MIN / MAX
Aggregate functions perform calculations on multiple rows and return a single value — ideal for reports, summaries, and analysis. 🔹 Syntax & Examples 🔹…
SQL DELETE
The DELETE statement is used to remove one or more rows from a table. 🔹 Basic Syntax ⚠️ Always use a WHERE clause to…
SQL UPDATE
The UPDATE statement is used to change data in existing rows of a table. 🔹 Basic Syntax ⚠️ Always use a WHERE clause unless…
SQL INSERT SELECT
INSERT SELECT is used to copy data from one table into another. This is very useful for data migration, backups, or transformations. 🔹 Basic…