Non-Equality Joins

With an equality join, the data value of a record stored in the common column for the first table must match the data value in the second table. However, in many cases, there’s no exact match. A non-equality join is used when the related columns can’t be joined with an equal sign—meaning there are no equivalent rows in the tables to be joined.

A non-equality join enables you to store a range’s minimum value in one column of a record and the maximum value in another column. So instead of finding a column-to column match, you can use a non-equality join to determine whether the item being shipped falls between minimum and maximum ranges in the columns.

Traditional Non-Equality JOIN =

SELECT b.title, p.gift
FROM books b, promotion p
WHERE b.retail BETWEEN p.minretail AND p.maxretail;

Non-Equality Joins: JOIN Method

SELECT b.title, p.gift
FROM books b JOIN promotion p
  ON b.retail BETWEEN p.minretail AND p.maxretail

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