It doesn’t arbitrarily double rows or something. For each row in the relation on the left of the join, it will produce 1 or more rows depending on how many rows in the relation on the right of the join match the join condition. The output relation of the join may have duplicate rows depending on the contents of each joined relation as well as what columns you are projecting from each.
If you want to remove duplicates, that’s what DISTINCT is for.
LEFT JOIN
Includes empty entries, doubles others.
…
It sure is long due for an overhaul.
That’s the whole point of a left join? Anything else wouldn’t be a left join anymore.
Well I didn’t expect doubles. I’m sure not an expert.
It doesn’t arbitrarily double rows or something. For each row in the relation on the left of the join, it will produce 1 or more rows depending on how many rows in the relation on the right of the join match the join condition. The output relation of the join may have duplicate rows depending on the contents of each joined relation as well as what columns you are projecting from each.
If you want to remove duplicates, that’s what
DISTINCTis for.Thanks, I will kot forget that the next time I have to do SQL!
Still wild there are no simpler language that have grown in popilarity for databases though.