Question

以下代码显示了某个项目的最长日期，并且一切正常。

    SELECT 
    pricing_id, pricing.field, pricing.region, price, max_date
FROM
    pricing
        INNER JOIN
    (SELECT 
        field, MAX(end_date) AS 'max_date'
    FROM
        pricing, regions
    GROUP BY field) AS tmptable ON tmptable.max_date = pricing.end_date
        AND tmptable.field = pricing.field
ORDER BY region, pricing.field

我正在尝试从regions.region_name中提取区域名称，以替换仅显示ID的pricing.region列。我已经尝试了通常的where子句来连接表并显示描述性名称，但它会破坏它。

有人可以帮忙吗？

谢谢，

约翰

Answer 1

您必须从区域表中选择region_name

类似

SELECT 
pricing_id, pricing.field, tmptable.region_name , price, max_date
FROM
pricing
    INNER JOIN
(SELECT 
   region_name , field, MAX(end_date) AS 'max_date'
FROM
    pricing, regions
GROUP BY field) AS tmptable ON tmptable.max_date = pricing.end_date
    AND tmptable.field = pricing.field
ORDER BY region, pricing.field

应该有用。

Answer 2

假设您的表在设置中类似，这应该有用。我假设你不想尝试在子选择中找到它，这似乎比需要更多的工作。相反，我将其添加为LEFT JOIN并将剩余的查询更改为匹配。

SELECT 
    pricing_id, pricing.field, r.region_name, price, max_date
FROM
    pricing
        INNER JOIN
    (SELECT 
        field, MAX(end_date) AS 'max_date'
    FROM
        pricing
    GROUP BY field) AS tmptable ON tmptable.max_date = pricing.end_date
        AND tmptable.field = pricing.field
LEFT JOIN regions r ON r.id = pricing.region
ORDER BY r.region_name, pricing.field

链接到另一个表以获取内部联接的名称

2 个答案: