我正在尝试创建一个查询
,它将用作显示信息的过滤器。
具体来说,我希望此查询最多显示具有相同 position
值的 2 行。
到目前为止我已经编写了这段代码,但它只显示了每个类别中的一个,我不确定我做错了什么,你能帮帮我吗?
SELECT name, surname, position, value, points FROM
(SELECT name, surname, position, value, points,
@num := IF(@type = position, @num + 1, 1) AS row_number,
@type := position AS dummy
FROM players
WHERE (name LIKE '%$searchphrase%' OR surname LIKE '%$searchphrase%')
AND value >= '$minvalue'
AND value <= '$maxvalue'
GROUP BY position) AS x WHERE x.row_number <= 2
ORDER BY
CASE WHEN $filter=0 THEN points END DESC,
CASE WHEN $filter=1 THEN points END ASC,
CASE WHEN $filter=2 THEN value END DESC,
CASE WHEN $filter=3 THEN value END ASC,
CASE WHEN $filter=4 THEN surname END DESC,
CASE WHEN $filter=5 THEN surname END ASC
最佳答案
你的想法是正确的。但是,MySQL 不保证表达式求值的顺序。另外,您在子查询中有一个按位置分组
。
所以我想你可能想要:
SELECT . . .
FROM (SELECT name, surname, position, value, points,
(@num := if(@type = position, @num + 1,
if(@type := position, 1, 1)
)
) AS row_number
FROM players p CROSS JOIN
(SELECT @num := 0, @type := '') params
WHERE (name LIKE '%$searchphrase%' OR surname LIKE '%$searchphrase%') AND
value >= '$minvalue' AND value <= '$maxvalue'
ORDER BY position
) x
WHERE x.row_number <= 2
关于MySQL - 从每个 'group' 中仅选择 2 行,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/46310118/