Melkij

select /**/ from `object_log`
    join (
        select max(id) as id 
            from `object_log`
            group by `id_gsm`
) lastevents using(id)
ORDER BY `id_gsm` ASC

where FIND_IN_SET('доставка2', delivery_type) or FIND_IN_SET('доставка3', delivery_type)

select /**/ from tablename join (
    select id_client, max(next_talk_date) as last_date from tablename where id_client in (/**/) group by id_client
) lastdate using(id_client)
where id_client in (/**/) and next_talk_date >= CURRENT_DATE and (next_talk_date = last_date or next_talk_date > CURRENT_DATE)

select /**/ from tablename t
where id_client in (/**/) and (
    next_talk_date > CURRENT_DATE or not exists (
        select 1 from tablename n 
        where n.id_client = t.id_client and n.next_talk_date > t.next_talk_date
    )
)

update tablename set fieldname = concat('prepend', fieldname) where /**/;

WHERE 
        uid IN (1,2,3,4,5) AND reg IN (1,2,3) AND date_last < SUBDATE(CURRENT_DATE, reg)

uid IN (1,2,3,4,5) AND (
        (reg=1 AND date_last < NOW() - INTERVAL 1 DAY)
        OR
        (reg=2 AND date_last < NOW() - INTERVAL 2 DAY)
        OR
        (reg=3 AND date_last < NOW() - INTERVAL 3 DAY)
)

Persistent connections were designed to have one-to-one mapping to regular connections. That means that you should always be able to replace persistent connections with non-persistent connections, and it won't change the way your script behaves. It may (and probably will) change the efficiency of the script, but not its behavior!

INSERT INTO pm (to,author,time,title,content) 
SELECT id, :author, :sendtime, :title, :message
    FROM users

->where(['show'=>1, 'hashtags_mid.hash' => ['yii', 'три']])

delete from users where lastvisit IS NULL and create_time < now() - interval '3 day'