数据库查询根据最后一次开始日期获得最低价格

Question

我希望根据各个经销商的上次抓取日期获得最低价格的产品。我当前的功能是非常基本的，它从表中获得最低价格而不考虑经销商ID和爬行时间戳。

我粗略地认为我们可以SELECT * FROM "custom_data_table"并使用php处理数据。请仔细阅读附件以进一步说明。

function get_lowest_price($table_id) {
    global $wpdb;
    $table_prices = $wpdb->get_results(
        $wpdb->prepare(
            "SELECT price FROM `custom_data_table` WHERE tableid= %d"
            ,$table_id)
    );
    if (!empty($table_prices) && $table_prices !== NULL) 
        return rtrim(min($table_prices)->price, '00');
}

Answer 1

这里的正确查询是：

SELECT price
FROM custom_data_name cdn, (
     SELECT MAX(crawled) AS maxCrawled, resellerid
     FROM custom_data_name
     GROUP BY resellerid
) cdnFiltered
WHERE cdn.crawled = cdnFiltered.maxCrawled AND
cdn.resellerid = cdnFiltered.resellerid AND
tableid = %d;

Answer 2

试试这个：

SELECT B.price 
FROM (SELECT resellerid, MAX(crawled) max_crawled
      FROM custom_data_table
      GROUP BY resellerid) A
JOIN custom_data_table B 
ON A.resellerid=B.resellerid AND A.max_crawled=B.crawled;

Answer 3

也许使用ORDER BY抓取和LIMIT 1