MySQL-Abfrage verwendet nicht den Index

Question

ich unter Abfrage haben:

SELECT bank_code, bank_name 
FROM system_bank_info 
WHERE company_id=1 AND country_id=103 AND status='ACTIVE' 
GROUP BY bank_name 
ORDER BY bank_name ASC 

TABLE SCHEMA:

CREATE TABLE `system_bank_info` (
    `id` int(11) NOT NULL AUTO_INCREMENT, 
    `company_id` int(11) NOT NULL, 
    `country_id` int(11) NOT NULL, 
    `bank_code` varchar(50) NOT NULL, 
    `bank_name` varchar(255) NOT NULL, 
    `branch_code` varchar(50) NOT NULL, 
    `branch_name` varchar(255) NOT NULL, 
    `status` enum('ACTIVE','INACTIVE') NOT NULL DEFAULT 'ACTIVE', 
    `bank_state` varchar(255) DEFAULT NULL, 
    `bank_district` varchar(255) DEFAULT NULL, 
    `bank_city` varchar(255) DEFAULT NULL, 
    `bank_address` text, 
    `bank_contact` varchar(255) DEFAULT NULL, 
    `service_type` enum('INSTA_CREDIT') DEFAULT NULL, 
    PRIMARY KEY (`id`), 
    KEY `country_id` (`country_id`), 
    KEY `bank_code` (`bank_code`), 
    KEY `branch_code` (`branch_code`), 
    KEY `company_id_country_id_status` (`company_id`,`country_id`,`status`), 
    CONSTRAINT `system_bank_info_ibfk_1` FOREIGN KEY (`company_id`) REFERENCES `company` (`id`), 
    CONSTRAINT `system_bank_info_ibfk_2` FOREIGN KEY (`country_id`) REFERENCES `system_country_list` (`country_id`) 
) ENGINE=InnoDB AUTO_INCREMENT=150398 DEFAULT CHARSET=utf8 

ERKLÄREN:

+----+-------------+------------------+------+-----------------------------------------+------------+---------+-------+-------+----------------------------------------------+ 
| id | select_type | table   | type | possible_keys       | key  | key_len | ref | rows | Extra          | 
+----+-------------+------------------+------+-----------------------------------------+------------+---------+-------+-------+----------------------------------------------+ 
| 1 | SIMPLE  | system_bank_info | ref | country_id,company_id_country_id_status | country_id | 4  | const | 59324 | Using where; Using temporary; Using filesort | 
+----+-------------+------------------+------+-----------------------------------------+------------+---------+-------+-------+----------------------------------------------+ 

Wie man dort sehen kann ein Index genannt company_id_country_id_status. Aber Abfrage verwendet immer noch country_id nur. Wie kann ich diese Abfrage effizienter machen?

Ich habe auch versucht, Indizes bank_code und bank_name hinzuzufügen. Aber, das gleiche Ergebnis!

Answer 1

Sie können dem Optimierer Hinweise geben, so dass er einen bestimmten Index verwendet. USE INDEX()

SELECT bank_code, bank_name 
FROM system_bank_info USE INDEX (company_id_country_id_status) 
WHERE company_id=1 AND country_id=103 AND status='ACTIVE'