![]() Left outer join r2021 r2 on r1.id = r2. Right outer join r2021 r2 on r1.id = r2.id Left outer join r2021 r2 on r1.id = r2.id Insert into r2021 values (108,'Ray Rama',2) Insert into r2021 values (103,'Tom Talla',2) Insert into r2021 values (102,'Ken Krishna',1) Insert into r2020 values (109,'Kat Krishna',4) Ĭreate table r2021 (id int, name varchar2(50),rank number) Insert into r2020 values (108,'Ray Rama',2) Insert into r2020 values (102,'Ken Krishna',3) Insert into r2020 values (101,'Rob Rama',1) As such, implicit JOINs are generally recommended against in favor of explicit syntax.Ĭreate table r2020 (id int, name varchar2(50),rank number) Query statements scan one or more tables or expressions and return the computed result rows. ![]() Implicit JOINs can be more difficult to read and comprehend, and they also have a few limitations since the join conditions are mixed in other WHERE conditions. GoogleSQL is the new name for Google Standard SQL New name, same great SQL dialect. The join conditions are specified in a WHERE clause.Įxplicit JOINs associate join conditions with a specific table's inclusion instead of in a WHERE clause. Implicit JOINs simply list all tables together. They are different styles of writing JOINs, but they are functionally equivalent. The two styles of JOIN are implicit JOINs and explicit JOINs. If (+) is on the left, it's a RIGHT JOIN.) (Specifically, if the (+) is on the right, it's a LEFT JOIN. (See higher up in my answer for more info about that.) The placement of the (+) determines RIGHT or LEFT. I've seen some confusion about what matters in determining RIGHT vs LEFT in implicit join syntax.Īll I did is swap sides of the terms in the WHERE clause, but they're still functionally equivalent. What matters is that you understand the concept of how it works. To clarify, I guess I'm saying that terminology doesn't matter, as it's only there to help visualize. See this example from for additional explanation. So in a P LEFT OUTER JOIN S, P will always have a record because it's on the LEFT, but S could be null. In the terminology, RIGHT or LEFT specify which side of the join always has a record, and the other side might be null. In your second query, it's S RIGHT OUTER JOIN P. So in your first query, it's a P LEFT OUTER JOIN S. In Oracle, (+) denotes the "optional" table in the JOIN. TableA LEFT OUTER JOIN TableB is equivalent to TableB RIGHT OUTER JOIN Table A.
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