Александр

Keep in mind also that MyISAM keeps data and indexes in two separate files (.MYD for data, .MYI for indexes), so it would be trivial to disable and enable indexes. InnoDB keeps the PRIMARY KEY and row data in the same InnoDB pages (via the Clustered Index). Secondary indexes will carry the PRIMARY KEY as an attachment to every secondary index leaf entry. Since the data and indexes are intertwined via the Clustered Index, no one has, as of yet, attempted to implement DISABLE KEYS and ENABLE KEYS in InnoDB.

SELECT * FROM `table` 
WHERE `time` BETWEEN '2018-08-09 00:00:00' AND '2018-08-09 23:59:59';

SELECT * FROM `table` WHERE DATE(`time`) = '2018-08-09';

UPDATE `table_name` SET `priority` = '', `content` = '192.166.45.67', `host` = 'ns2' WHERE `domain` = 'yandex.ru'

$result = $db->query('SELECT p.id, p.name, c.name, p.price, p.code FROM product as p, category_id as c WHERE c.id = p.category_id');
...

$result = $db->query('SELECT p.id, p.name, c.name, p.price, p.code FROM product as p LEFT JOIN category as c ON p.category_id = c.id');
...

$productsList[$i]['p.category_id'] = $row['c.category_id'];

SELECT * FROM `table` WHERE '2016-11-22' BETWEEN `date_in` AND `date_out`

mysql -u username -p database_name < backup_name.sql

A LEFT [OUTER] JOIN can be faster than an equivalent subquery because the server might be able to optimize it better—a fact that is not specific to MySQL Server alone.