Boolean Logic in SQL

This chapter is from the book

The Language of SQL, 3rd Edition

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This chapter is from the book

This chapter is from the book 

The Language of SQL, 3rd Edition

Learn More Buy

The AND Operator

The following examples will be taken from this Purchases table:

Here’s an example of a WHERE clause that uses the AND operator:

SELECT
CustomerName,
QuantityPurchased
FROM Purchases
WHERE QuantityPurchased > 3
AND QuantityPurchased < 7

The AND clause means that all conditions must evaluate to true for the row to be selected. This SELECT specifies that the only rows to be retrieved are those for which the QuantityPurchased is both greater than 3 and less than 7. Therefore, only these two rows are returned:

Notice that the row for Sandy Harris is not returned. Why? Sandy purchased a quantity of 10, which, in fact, does satisfy the first condition (QuantityPurchased > 3). However, the second condition (QuantityPurchased < 7) is not satisfied and therefore is not true. When using the AND operator, all conditions specified must be true for the row to be selected.