SQL EQUI JOIN
SQL EQUI JOIN is a specific type comparison base join (equally comparison) not allowing other comparison operator such as <, > <= etc. And create record set result that are combining columns value from the tables (two or more table).
Example Table
Considering following category, product is our example table.
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SQL Equi join use JOIN keyword specify table name and ON keyword specify the join predicate condition.
Example
SQL> SELECT *
FROM product JOIN category
ON product.category_id = category.category_id;
CATEGORY_ID PRODUCT_NAME CATEGORY_ID CATEGORY_NAME
----------- --------------------- ----------- ---------------------
1 Nokia 1 Mobiles
1 Samsung 1 Mobiles
2 HP 2 Laptops
2 Dell 2 Laptops
3 Apple 3 Tablet
4 Nikon 4 Cameras
6 rows selected.
You can also write Equi join as following way.
Example
SQL> SELECT *
FROM product, category
WHERE product.category_id = category.category_id;
CATEGORY_ID PRODUCT_NAME CATEGORY_ID CATEGORY_NAME
----------- --------------------- ----------- ---------------------
1 Nokia 1 Mobiles
1 Samsung 1 Mobiles
2 HP 2 Laptops
2 Dell 2 Laptops
3 Apple 3 Tablet
4 Nikon 4 Cameras
6 rows selected.
If join predicate condition both table column name are same, then you can write this query shorthand way by using USING Keyword.
Example
SQL> SELECT *
FROM product
INNER JOIN category USING (category_id);
CATEGORY_ID PRODUCT_NAME CATEGORY_ID CATEGORY_NAME
----------- --------------------- ----------- ---------------------
1 Nokia 1 Mobiles
1 Samsung 1 Mobiles
2 HP 2 Laptops
2 Dell 2 Laptops
3 Apple 3 Tablet
4 Nikon 4 Cameras
6 rows selected.