Question

这是我要运行的查询：

SELECT
    o.id,
    history.name,
    history.id AS historyId
FROM
    order_sheet AS o
LEFT JOIN(
    SELECT
        h.detail,
        h.eid,
        h.date_change
    FROM
        order_history AS h
    WHERE
        h.id_order_sheet = o.id
    ORDER BY
        h.id
    DESC
    LIMIT 0, 1
) history
ON
    history.id_order_sheet = o.id
ORDER BY
    o.id
LIMIT 0, 150;

第二个选择中的我的问题。它不知道o.id。

请问您知道如何执行此操作吗？

我将解释我该怎么做：）

我要选择插入到表 order_history 中的最后一个元素，其值为 order_history.id_order_sheet ===到order_sheet.id < / p>

谢谢您的帮助

Answer 1

您可以在下面尝试

SELECT
    o.id,
    history.name,
    history.id AS historyId
FROM
    order_sheet AS o
LEFT JOIN(
    SELECT
        h.detail,
        h.eid,
        h.date_change
    FROM
        order_history AS h join order_sheet o1
    on
        h.id_order_sheet = o1.id
    ORDER BY
        h.id
    DESC
    LIMIT 0, 1
) history
ON
    history.id_order_sheet = o.id
ORDER BY
    o.id
LIMIT 0, 150;

Answer 2

我们可能会使用不相关的子查询来重写您的联接：

SELECT
    o.id,
    h2.name,
    h2.id AS historyId
FROM order_sheet AS o
LEFT JOIN
(
    SELECT id_order_sheet, MAX(id) AS max_id
    FROM order_history
    GROUP BY id_order_sheet
) h1
    ON o.id = h1.id_order_sheet
INNER JOIN order_history h2
    ON h1.id_order_sheet = h2.id_order_sheet AND h1.id = h2.max_id
ORDER BY
    o.id
LIMIT 0, 150;

Answer 3

您要尝试做的是横向联接，而MySQL目前尚不支持。

但是，不难获得每个订单ID的最新历史记录。您不需要加入。

select id_order_sheet, name, id as history_id
from order_history
where id in (select max(id) from order_history group by id_order_sheet)
order by id_order_sheet;

Answer 4

很明显我无法测试，但这是一种方法：

SELECT
    o.id,
    h.name,
    h.id AS history_id,
    h.detail,
    h.eid,
    h.date_change
FROM order_sheet o
LEFT JOIN order_history h ON h.id_order_sheet = o.id
WHERE h.id IN (
    SELECT MAX(id)
    FROM order_history
    GROUP by id_order_sheet
);

使用MySQL的特定联接

4 个答案: