SQL Server LEFT JOIN compared to LEFT OUTER JOIN - Any difference?

Data and Databases
1

I’m working on a database project and I keep seeing these two different ways to write joins in SQL Server queries. Some developers use LEFT JOIN while others write LEFT OUTER JOIN. I’m confused about whether these are actually different operations or if they do the same thing.

Can someone explain if there’s any practical difference between using LEFT JOIN and LEFT OUTER JOIN in SQL Server? Are they just different syntax for the same operation, or do they behave differently in certain situations?

For example:

SELECT u.username, p.post_title
FROM users u
LEFT JOIN posts p ON u.user_id = p.author_id;

versus:

SELECT u.username, p.post_title
FROM users u
LEFT OUTER JOIN posts p ON u.user_id = p.author_id;

Which one should I use in my queries?

2

good question! i was wonderin the same thing. both queries give the same results in sql server - the OUTER keyword is just optional, so most skip it for ease. have u noticed any performance diff in ur projects?

3

they’re the same thing - just different syntax. sql server doesn’t care which one you use since both give identical results and performance. i stick with left join because it’s shorter and looks cleaner.

4

There’s no difference between LEFT JOIN and LEFT OUTER JOIN in SQL Server. They’re identical - LEFT JOIN is just shorthand for LEFT OUTER JOIN. The query optimizer treats them the same and generates identical execution plans. I’ve been using SQL Server for years and started with LEFT OUTER JOIN because it seemed more explicit. But I switched to LEFT JOIN since it’s shorter and that’s what most developers use. Every codebase I’ve worked with uses the shorter syntax. Same thing applies to RIGHT JOIN vs RIGHT OUTER JOIN and FULL JOIN vs FULL OUTER JOIN. Pick one and stick with it throughout your project - consistency makes code easier to read and maintain.