Summary: in this tutorial, you will learn how to use the Db2 AND operator to combine multiple Boolean expressions.
Introduction Db2 AND operator
The AND operator is a logical operator that combines two Boolean expressions or predicates. You use the AND operator to specify that a search must satisfy both conditions.
The following illustrates the AND operator syntax:
1 | boolean_expression1 AND boolean_expression2 |
In this syntax, the boolean_expression1 and boolean_expression2 evaluate to true, false, and unknown.
This table displays the result when combining true, false, and unknown values using the AND operator:
| TRUE | FALSE | UNKNOWN | |
|---|---|---|---|
| TRUE | TRUE | FALSE | UNKNOWN |
| FALSE | FALSE | FALSE | FALSE |
| UNKNOWN | UNKNOWN | FALSE | UNKNOWN |
If you use both AND and OR operators in an expression, Db2 evaluates the AND operator first. However, you can change the order of evaluation using parentheses.
To negate the AND operator, you use the NOT operator as follows:
1 | NOT (boolean_expression1 AND boolean_expression2) |
The AND operator is often used in the WHERE clause to form the search condition for the SELECT, UPDATE, and DELETE statement.
Db2 AND operator examples
Let’s use the books table from the sample database for the demo.
1) Db2 AND operator example
This example uses the AND operator to find the books whose ratings are between 4 and 5:
1 2 3 4 5 6 7 8 9 10 | SELECT title, rating, total_pages FROM books WHERE rating >= 4 AND rating <= 5 ORDER BY title; |
Here is the result set:
2) Using multiple Db2 AND operators example
This example uses two AND operators to find books whose ratings are between 4 and 5 and the number of pages is greater than 1300:
1 2 3 4 5 6 7 8 9 10 | SELECT title, rating, total_pages FROM books WHERE rating >= 4 AND rating <= 5 AND total_pages > 1300 ORDER BY title; |
The output is as follows:
3) Using Db2 AND operator with parentheses
If you use the AND and OR operators with more than two conditions, you can use parentheses to explicitly specify the order in which you want Db2 to evaluate the conditions.
This example uses both AND and OR operators to find books that satisfy both the following conditions:
- The number of pages is greater than 1,000 and less than 1,200
- Rating is greater than 4.7
Query:
1 2 3 4 5 6 7 8 9 10 11 | SELECT title, total_pages, rating FROM books WHERE(total_pages < 1200 AND total_pages > 1000) OR rating > 4.7 ORDER BY rating DESC; |
If you move the parentheses, the meaning of the WHERE clause can change significantly:
1 2 3 4 5 6 7 8 9 10 11 | SELECT title, total_pages, rating FROM books WHERE total_pages < 1200 AND (total_pages > 1000 OR rating > 4.7) ORDER BY rating DESC; |
This query returns books that satisfy both the following conditions:
- The number of pages is less than 1200
- The number of pages is greater than 1000 or rating is greater than 4.7
4) Using Db2 NOT AND operator example
This example uses the NOT AND operator to find books that have the number of pages less than or equal 500 or rating greater than 4.7:
1 2 3 4 5 6 7 8 9 10 11 | SELECT title, total_pages, rating FROM books WHERE NOT(total_pages > 500 AND rating < 4.7) ORDER BY total_pages DESC, rating DESC; |
Here is the result set:
Notice that based on De Morgan’s laws, NOT (A AND B) is equivalent to (NOT A OR NOT B)
In this tutorial, you have learned how to use the Db2 AND operator to form a search condition that combines two Boolean expressions.