查询返回所有行

Question

Why does this query returns me all the rows matching my OR LIKE condition and jumps over doctorLang . city . What I mean is I get all the rows in all towns not in only certain one.

SELECT `doctor`.`id`, `doctorLang`.`first_name`, `doctorLang`.`second_name`, `doctorLang`.`city`, `doctorLang`.`hospital_name`
FROM `doctor` LEFT JOIN `doctorLang` ON `doctor`.`id`=`doctorLang`.`doc_id`
WHERE `doctorLang`.`city`='Пловдив' 
AND `doctorLang`.`language`='bg' 
AND `doctor`.`active`=1
AND `doctorLang`.`first_name` LIKE '%йло'
OR `doctorLang`.`first_name` LIKE '%йло%'
OR `doctorLang`.`first_name` LIKE 'йло%'
OR `doctorLang`.`second_name` LIKE '%йло'
OR `doctorLang`.`second_name` LIKE '%йло%'
OR `doctorLang`.`second_name` LIKE 'йло%'
OR `doctorLang`.`third_name` LIKE '%йло'
OR `doctorLang`.`third_name` LIKE '%йло%'

Answer 1

Here is a version of your WHERE clause which should behave as expected:

WHERE
    doctorLang.city = 'Пловдив' AND
    doctorLang.language = 'bg'  AND
    doctor.active = 1           AND
    (
        doctorLang.first_name LIKE '%йло'   OR
        doctorLang.first_name LIKE '%йло%'  OR
        doctorLang.first_name LIKE 'йло%'   OR
        doctorLang.second_name LIKE '%йло'  OR
        doctorLang.second_name LIKE '%йло%' OR
        doctorLang.second_name LIKE 'йло%'  OR
        doctorLang.third_name  LIKE '%йло'  OR
        doctorLang.third_name LIKE '%йло%'
    )

Your original WHERE clause, without parentheses, was being interpreted as this:

WHERE
    (
        doctorLang.city = 'Пловдив' AND
        doctorLang.language = 'bg'  AND
        doctor.active = 1           AND
        doctorLang.first_name LIKE '%йло'
    )
    OR
        doctorLang.first_name LIKE '%йло%'  OR
        doctorLang.first_name LIKE 'йло%'   OR
        ...

In other words, if even one of the OR conditions involving the name were true, it would cause all rows to be returned, apparently ignoring your other restrictions.

The take home lesson here is that AND has higher precedence , or order of execution, than OR . But we can impose any evaluation order we want by using parentheses.

Answer 2

It is working for an or condition actually its like city='something' or name='something'

use a subquery instead

first fetch for the town you are looking for and then from that result for the names you are looking for

hope it helps