EXISTS vs JOIN and use of EXISTS clause

Question

Below is the code sample:

CREATE TABLE #titles(
    title_id       varchar(20),
    title          varchar(80)       NOT NULL,
    type           char(12)           


        

Answer 1

• EXISTS is a semi-join
• JOIN is a join

So with 3 rows and 5 rows matching

• JOIN gives 15 rows
• EXISTS gives 3 rows

The result is the "short circuit" effect mentioned by others and no need to use DISTINCT with a JOIN. EXISTS is almost always quicker when looking for existence of rows on the n side of a 1:n relationship.