oracle - Differences between joins and sets in sql? -


what main differences between joins(inner join,left outer join, right outer join etc.) , set operations( intersect, minus etc.) ?

first of all, joins , set operations 2 different kettles of fish. joins can allow filter rows between sets, it's true, they're more (you can make wider row joining tables , selecting columns across tables, whereas set operations work on sets of rows same width).

the way mentally picture things joins horizontal (ie. rows table1 next matching rows table2, next matching rows table 3 etc), whereas set operations vertical (as in rows second set underneath rows first set). when choose use set operations on joins highly dependent on situation. kind of deciding whether use hammer or screwdriver secure 2 bits of wood - use hammer drive screw wood?

secondly, oracle has (well, since @ least version 7!) had joins. joins fundamental how relational databases work!

i guess you're asking why did oracle introduce ansi syntax joins, , guess (you'd have ask larry full reasons!) bring oracle in line ansi standards joins, many other rdbms platforms have adopted.


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