如何使用多个 JOIN 加快 SQL 查询？

Question

The below SQL query took 8.0943 seconds to execute. Is there a better way to speed this up?

SELECT 
       e.idno, e.estatus,
       p.idno, p.id, p.time, p.date, p.employee, p.status, p.comment
       FROM e_company_data e
       INNER JOIN people_attendance p ON p.idno = e.idno
       WHERE p.id = (SELECT MAX(id) FROM people_attendance p1
                            WHERE p1.idno = p.idno)
       AND e.estatus = 1 ORDER BY e.idno

I have already indexed the following.

Table: people_attendance Columns: idno, date, time, employee, status, comment

Table: e_company_data Columns: idno, estatus

I might have done wrong on the indexes. Any help would be greatly appreciated. Thanks.

(From pastebin)

CREATE TABLE `people_attendance` (
 `id` int(11) NOT NULL AUTO_INCREMENT,
 `reference` int(11) DEFAULT NULL,
 `idno` varchar(11) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
 `date` date DEFAULT NULL,
 `employee` varchar(80) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
 `status` varchar(15) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
 `time` time DEFAULT NULL,
 `comment` varchar(80) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
 `reason` varchar(80) COLLATE utf8mb4_unicode_ci NOT NULL,
 `counter` int(11) DEFAULT NULL,
 PRIMARY KEY (`id`),
 KEY `idxidno` (`idno`),
 KEY `idxattendance` (`employee`,`status`,`date`,`time`,`comment`) USING BTREE
) ENGINE=MyISAM AUTO_INCREMENT=12888 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci

CREATE TABLE `e_company_data` (
 `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
 `reference` int(11) NOT NULL,
 `company` varchar(255) COLLATE utf8mb4_unicode_ci DEFAULT \'\',
 `department` varchar(255) COLLATE utf8mb4_unicode_ci DEFAULT \'0\',
 `jobposition` varchar(255) COLLATE utf8mb4_unicode_ci DEFAULT \'\',
 `companyemail` varchar(255) COLLATE utf8mb4_unicode_ci DEFAULT \'\',
 `idno` varchar(255) COLLATE utf8mb4_unicode_ci DEFAULT \'\',
 `pin` varchar(4) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
 `startdate` varchar(255) COLLATE utf8mb4_unicode_ci DEFAULT \'\',
 `dateregularized` varchar(255) COLLATE utf8mb4_unicode_ci DEFAULT \'\',
 `reason` varchar(455) COLLATE utf8mb4_unicode_ci DEFAULT \'\',
 `leaveprivilege` int(11) DEFAULT NULL,
 `estatus` int(2) NOT NULL,
 PRIMARY KEY (`id`),
 KEY `idxcompdata` (`idno`,`department`,`estatus`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=130 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci

Answer 1

Possibly using window functions:

SELECT e.idno, e.estatus,
       p.idno, p.id, p.time, p.date, p.employee, p.status, p.comment
FROM e_company_data e JOIN
     (SELECT p.*, ROW_NUMBER() OVER (PARTITION BY p.idno ORDER BY p.id DESC) as seqnum
      FROM people_attendance p
     ) p
     ON p.idno = e.idno AND seqnum = 1
WHERE e.estatus = 1
ORDER BY e.idno;

This should benefit from indexes on people_attendance(idno, id desc) and e_company_data(status, idno) .

EDIT:

For your version of the query:

SELECT e.idno, e.estatus,
       p.idno, p.id, p.time, p.date, p.employee, p.status, p.comment
FROM e_company_data e JOIN
     people_attendance p
     ON p.idno = e.idno
WHERE p.id = (SELECT MAX(p2.id)
              FROM people_attendance p2
              WHERE p2.idno = p.idno
             ) AND
      e.estatus = 1
ORDER BY e.idno;

I would recommend indexes on e_company_data(status, idno) and people_attendance(idno, id) .

Answer 2

Give this a try:

SELECT  e.idno, e.estatus, p.idno, p.id, p.time, p.date, p.employee,
        p.status, p.comment
    FROM  ( SELECT idno, MAX(id) AS last_id
                 FROM people_attendance
                 GROUP BY idno ) AS x
    JOIN  e_company_data e  USING(idno)
    JOIN  people_attendance p  ON p.id = x.last_id
    WHERE  e.estatus = 1
    ORDER BY  e.idno

The principle is to turn the correlated subquery into a derived table. Instead of 130 probes, it is one quick scan of a covering INDEX(idno, id) to get the 130 rows. After that, the rest is efficient JOINs.

Also, add INDEX(idno, status) (in either order) to e_company_data .

Answer 3

In addition to Rick James answer, keep in mind that your query is slow on agregate function "SELECT MAX(id)". Think about to add field which on update would keep max(id).