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Using MySQL SELECT for simple BOOLEAN evaluation?
You can use CASE statement for this. Let us see an example −
mysql> create table BooleanEvaluationDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> FirstValue int, -> SecondValue int -> ); Query OK, 0 rows affected (0.71 sec)
Insert some records in the table using insert command. The query is as follows −
mysql> insert into BooleanEvaluationDemo(FirstValue,SecondValue) values(10,5); Query OK, 1 row affected (0.20 sec) mysql> insert into BooleanEvaluationDemo(FirstValue,SecondValue) values(15,20); Query OK, 1 row affected (0.16 sec) mysql> insert into BooleanEvaluationDemo(FirstValue,SecondValue) values(50,40); Query OK, 1 row affected (0.14 sec) mysql> insert into BooleanEvaluationDemo(FirstValue,SecondValue) values(500,1000); Query OK, 1 row affected (0.13 sec)
Display all records from the table using select statement. The query is as follows −
mysql> select *from BooleanEvaluationDemo;
Here is the output −
+----+------------+-------------+ | Id | FirstValue | SecondValue | +----+------------+-------------+ | 1 | 10 | 5 | | 2 | 15 | 20 | | 3 | 50 | 40 | | 4 | 500 | 1000 | +----+------------+-------------+ 4 rows in set (0.00 sec)
The following is the query to SELECT for simple BOOLEAN evaluation −
mysql> SELECT FirstValue,SecondValue,CASE WHEN FirstValue > SecondValue THEN 'true' ELSE 'false' END AS FirstValuesGreaterThanSecond from BooleanEvaluationDemo;
Here is the output −
+------------+-------------+-------------------------------+ | FirstValue | SecondValue | FirstValuesGreaterThanSecond | +------------+-------------+-------------------------------+ | 10 | 5 | true | | 15 | 20 | false | | 50 | 40 | true | | 500 | 1000 | false | +------------+-------------+-------------------------------+ 4 rows in set (0.00 sec)
Updated on: 30-Jul-2019
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