cheatsheets/sql-join.md

title	layout	updated	weight
SQL joins	2017/sheet	2017-10-30	-1

Example

SELECT * FROM order_items \
  LEFT OUTER JOIN orders \
  ON order_items.order_id = orders.id

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Joins are typically added to SELECT statements to add more columns and records.

Diagram

SELECT * FROM `A` INNER JOIN `B`

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┌────────┐
│ A  ┌───┼────┐
│    │ ∩ │    │
└────┼───┘  B │
     └────────┘

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Join	What
Inner join	∩
Left outer join	A + ∩
Right outer join	∩ + B
Full outer join	A + ∩ + B