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? ??? ??? MySQL ???? MySQL? ? ???? ??? ?? ??? ????? ???? ??? ??????

MySQL? ? ???? ??? ?? ??? ????? ???? ??? ??????

Dec 28, 2024 am 12:23 AM

How to Efficiently Query One Random Item from Each Category in MySQL?

? MYSQL ???? ??? ?? ??

?????? ?????? ? ???? ??? ???? ???? ?? ???? ????? ?????. ?? ??? ID? ?? ??? ????? ??? ??? ???? Items ???? ?? ??????? ??? ???. ??? ??? ???? ???? ????? ??? ID? ?????.

?????? ?? ??? ???? ???? ?? ???? ????? ??? ??? ? ????.

?? ??? ??? ?????. ??? ?? ????? ???? ???? ID? ???? ???:

SELECT
c.id AS cid, c.category, i.id AS iid, i.name
FROM categories c
INNER JOIN items i ON c.id = i.category

??? ?? ?? ????? ?? ?? ??? ??? ?? ??? ?????.

?? ?? ??? ?????? ?? ORDER BY RAND():

SELECT
c.id AS cid, c.category, i.id AS iid, i.name
FROM categories c
INNER JOIN items i ON c.id = i.category
ORDER BY RAND()

? ????? ??? ???? ???? ?? ???? GROUP BY:

SELECT * FROM (
    SELECT
    c.id AS cid, c.category, i.id AS iid, i.name
    FROM categories c
    INNER JOIN items i ON c.id = i.category
    ORDER BY RAND()
) AS shuffled_items
GROUP BY cid
? ??? ???? ??? ??? ???? ID?? ????? ????? ? ??? ? ?? ??? ?????. ??? ??? ?? ?? ????? ? ?? ??? ??? ??? ?????.

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