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- Update some sheets which have very long sections - Remove `layout: 2017/sheet` (everything has the same layout now) - Remove outdated sheets
796 B
796 B
title, category, updated, weight
title | category | updated | weight |
---|---|---|---|
SQL joins | Databases | 2018-12-06 | -1 |
Example
SELECT * FROM order_items \
LEFT OUTER JOIN orders \
ON order_items.order_id = orders.id
{: .-wrap}
Joins are typically added to SELECT
statements to add more columns and records.
Diagram
SELECT * FROM `A` INNER JOIN `B`
{: .-setup}
┌────────┐
│ A ┌───┼────┐
│ │ ∩ │ │
└────┼───┘ B │
└────────┘
{: .-box-chars.-setup}
Join | What |
---|---|
Inner join | ∩ |
Left outer join | A + ∩ |
Right outer join | ∩ + B |
Full outer join | A + ∩ + B |