Question

我创建了一个更新字段的查询。但我需要更改最后一条记录的值。在我的 ps_order_history 表中，有 date_add 列。它的类型是 datetime 。如果我不能在where子句中使用max（）函数，我怎么能得到最后一条记录？这是我到目前为止所得到的（有一些固定的参数，但它只是为了测试。我将在PHP代码中更改它）：

UPDATE ps_order_history AS h 
INNER JOIN ps_order_detail d ON d.id_order = h.id_order
INNER JOIN ps_orders o ON o.id_order = h.id_order
SET h.id_order_state = 18
WHERE d.product_name = "Academia Mastermaq"

AND o.id_customer = (
SELECT id_customer
FROM ps_customer
WHERE firstname = "Cristiano"
AND lastname = "Ferreira dos Santos"
)

AND max(h.date_add)

感谢。

Answer 1

您可以使用Order by xxx DESC LIMIT 1

来实现

Answer 2

知道了！我发现了MySQL中的变量并用一个来存储最大的id_order_history（我意识到我不需要date_add列，因为max id_order_history是最后一个数据）。之后，我更新了表格。

这是查询：

SET @maxid = 
(
    SELECT max(h.id_order_history)

    FROM ps_order_history h

    WHERE h.id_order =
    (
        SELECT max(p.id_order)
        FROM ps_orders p
        INNER JOIN ps_order_detail d ON d.id_order = p.id_order

        WHERE p.id_customer = 
        (
            SELECT id_customer
            FROM ps_customer
            WHERE firstname = '$firstname'
            AND lastname = '$lastname'
            LIMIT 1
        )

        AND d.product_name = '$nome_produto'
        AND p.module = 'pagseguro'

        LIMIT 1
    )
);

UPDATE ps_order_history h
SET h.id_order_state = $status
WHERE h.id_order_history = @maxid;

where子句中的Max（datetime列）

2 个答案: