SQL LEFT JOIN
SQL LEFT JOIN (SQL LEFT OUTER JOIN) always contains all records of left table (Table A) even of join condition does not find any matching record in right table (Table B).
SQL OUTER JOIN - OUTER JOIN is a join two table involving common attributes from two tables. But tables (Table A) does not require to have a matching value to other table (Table B).
Example Table
Considering following SQL left join example, category, product is our example table.
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Example
SQL> SELECT *
FROM product LEFT OUTER JOIN category
ON product.category_id = category.category_id;
CATEGORY_ID PRODUCT_NAME CATEGORY_ID CATEGORY_NAME
----------- ---------------------- ----------- ----------------------
1 Samsung 1 Mobiles
1 Nokia 1 Mobiles
2 Dell 2 Laptops
2 HP 2 Laptops
3 Apple 3 Tablet
4 Nikon 4 Cameras
NULL Playstation NULL NULL
7 rows selected.
Following is alternative syntax result produce same as above,
Example
SQL> SELECT *
FROM product, category
WHERE product.category_id = category.category_id(+);
CATEGORY_ID PRODUCT_NAME CATEGORY_ID CATEGORY_NAME
----------- ---------------------- ----------- ----------------------
1 Samsung 1 Mobiles
1 Nokia 1 Mobiles
2 Dell 2 Laptops
2 HP 2 Laptops
3 Apple 3 Tablet
4 Nikon 4 Cameras
NULL Playstation NULL NULL
7 rows selected.