Dragon Ball 2 part 2

Sets

Sets operation

are way to combine the results of two or more queries.

UNION

it combines results from two queries removes duplicates.

UNION ALL

it combines results from two queries keeps duplicates

Intersect

it returns only rows common to both queries

Inner Join

it returns only rows that have matching values in both tables.

Natural Join

Same as inner join, but SQL automatically joins on columns with the same name.

Left Join

it returns all rows from the left table (employees), plus matching rows from the right table. If no match, show NULL.

Right Join

it returns all rows from the right table (employees), plus matching rows from the left table. If no match, shows NULL.

Cross Join

it returns every combination of rows from both tables.

Views

use this when you want to save a query (with joins or subqueries) and reuse it later.