Vitsliputsli

WITH recursive hours (n) AS (
    SELECT (@q:=0) n FROM dual
    UNION ALL
    SELECT (@q:=@q+1) n FROM hours WHERE @q<24
)
SELECT hours.n, ваш_запрос.* FROM ваш_запрос
    RIGHT JOIN hours ON ваш_запрос.час = hours.n

WITH recursive hours (n) AS (
    SELECT CONCAT("0",CAST(@q:=0 as varchar(1))) n FROM dual
    UNION ALL
    SELECT LPAD(CAST(@q:=@q+1 as varchar(2)),2,"0") n FROM hours WHERE @q<24
)
SELECT hours.n, ваш_запрос.* FROM ваш_запрос
    RIGHT JOIN hours ON  ваш_запрос.час = hours.n

WITH discussion_count AS (
    SELECT count(*) cnt FROM discussion WHERE author_id=?
),
discussion_messages_count AS (
    SELECT count(*) cnt FROM discussion_messages WHERE author_id=?
)
SELECT 
        p.name, dc.cnt discussions, dmc.cnt dcount
    FROM people p, discussion_count dc, discussion_messages_count dmc
    WHERE p.id=?

SELECT
        table1.*
    FROM table1
    LEFT JOIN table2 ON table1.searchArticle=table2.searchArticle AND table1.brand=table2.brand
    WHERE table2.brand is null // здесь лучше указать table2.id

SELECT
    p.*
    FROM `таблица c постами` p
    JOIN `таблица с подписками` s ON p.user_id=s.followed_id
    WHERE s.user_id=:user_id

WITH news_images AS (
    SELECT news.id news_id, min(images.id) images_id FROM news
        LEFT JOIN images ON news.id=images.id
        GROUP BY news.id
        LIMIT 10
)
SELECT news.*,images.* 
    FROM news_images
    JOIN news ON news.id=news_images.news_id
    JOIN images ON images.id=news_images.images_id

WITH check_user as (
	SELECT :user_id IN (18,104,1,15) check_id FROM dual
),
main_query as (
	SELECT
	  kpi.id,
	  GROUP_CONCAT(users_to_groups.user_id) AS test_1,
	  SUM(:user_id=users_to_groups.user_id) AS test_3
	FROM kpi
	LEFT JOIN kpi_watchers_groups ON kpi_watchers_groups.kpi_id = kpi.id
	LEFT JOIN users_to_groups ON users_to_groups.data_id = kpi_watchers_groups.group_id
	GROUP BY kpi.id
)
SELECT
	main_query.*,
	check_user.check_id test_2
FROM main_query
CROSS JOIN check_user

$sel = mysql_query("
    SELECT DISTINCT(`seller_id`)
        FROM `oc_ms_seller`  
        WHERE categ REGEXP '(^|,)$cat_id($|,)'", $link);

JOIN users S on S.id=IF(93=sender_id, sender_id, recipient_id)
JOIN users R on R.id=IF(93=recipient_id, sender_id, recipient_id)