January 30th, 2009
JOIN versus WHERE (Part 2 of 3)
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L. JOINs
> Joins exist only for the duration of the query. They are not part of the database.
> Joined columns don’t need the same column name (except when doing a natural join).
> If a joining column contains a null, the null never joins.
> The joining columns must be compatible, such as (INTEGER, NUMERIC, FLOAT), (CHAR, VARCHAR), (DATE, TIME, TIMESTAMP).
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