Question

我有一个返回5列的查询。

其中一列显示行的最新日期值，其中一列包含字符串“seller-contact”或“buyer-contact”。

原始代码工作正常，看起来像这样。

descriptionLabel

我尝试使用两个子查询来实现上述结果。它不会失败或导致任何错误代码。但是在较大的LIVE数据库上，它花费的时间太长了（返回大约270行，我假设使用子查询会产生270 ^ 270x之前的时间;它永远不会完成它只是挂起）

if ([json valueForKey:@"unavailable"]) {
    UnavailableViewController* controller = [[UnavailableViewController alloc] init];
    controller.descriptionLabel.text = ([json valueForKey:@"unavailable_text"]) ? [json valueForKey:@"unavailable_text"] : @"We're temporarily unavailable, please try again later."; // just in case you forget to set it have a fallback.
    // present view controller...
}

有没有办法让事情更简单，所以我可以有一些看起来像

的东西

SELECT
  TRIM(p.title) AS `Property Address`,
  TRIM(us.name) AS `Staff`,

  DATE_FORMAT(FROM_UNIXTIME(MAX( n.datecreated)), '%d-%m-%Y') AS `Last Contact Note`,

  DATEDIFF(
    DATE_FORMAT(FROM_UNIXTIME(UNIX_TIMESTAMP(NOW())), '%Y-%m-%d'),
    DATE_FORMAT(FROM_UNIXTIME(MAX(n.datecreated)), '%Y-%m-%d')
  ) AS `Days Since Last Note`

FROM ias_property AS `p`
LEFT JOIN ias_note_stream AS `ns` ON ns.target_id = p.id
LEFT JOIN ias_note AS `n` ON ns.note_id = n.id
LEFT JOIN ias_user_staff AS `us` ON p.user_staff_id = us.id
WHERE p.status = 'sold' AND p.isarchived = 0
AND us.position = 'SP'
AND (n.data LIKE '%buyer-contact%' OR n.data LIKE '%seller-contact%')
GROUP BY p.id
ORDER BY MAX(n.datecreated) ASC

TLDR：如何将同一列中的WHERE子句的结果显示为两个单独的列（AS SELECT TRIM(p.title) AS `Property Address`, TRIM(us.name) AS `Staff`, (SELECT DATE_FORMAT(FROM_UNIXTIME(MAX(n.datecreated)), '%d-%m-%Y') FROM ias_property AS `p` LEFT JOIN ias_note_stream AS `ns` ON ns.target_id = p.id LEFT JOIN ias_note AS `n` ON ns.note_id = n.id WHERE n.data LIKE '%buyer-contact%' AND p.status = 'sold' AND p.isarchived = 0 AND us.position = 'SP' ) AS `Last Buyer Contact Note`, (SELECT DATE_FORMAT(FROM_UNIXTIME(MAX(n.datecreated)), '%d-%m-%Y') FROM ias_property AS `p` LEFT JOIN ias_note_stream AS `ns` ON ns.target_id = p.id LEFT JOIN ias_note AS `n` ON ns.note_id = n.id WHERE n.data LIKE '%seller-contact%' AND p.status = 'sold' AND p.isarchived = 0 AND us.position = 'SP' ) AS `Last Seller Contact Note`, DATEDIFF( DATE_FORMAT(FROM_UNIXTIME(UNIX_TIMESTAMP(NOW())), '%Y-%m-%d'), DATE_FORMAT(FROM_UNIXTIME(MAX(n.datecreated)), '%Y-%m-%d') ) AS `Days Since Last Note` FROM ias_property AS `p` LEFT JOIN ias_note_stream AS `ns` ON ns.target_id = p.id LEFT JOIN ias_note AS `n` ON ns.note_id = n.id LEFT JOIN ias_user_staff AS `us` ON p.user_staff_id = us.id WHERE p.status = 'sold' AND p.isarchived = 0 AND us.position = 'SP' AND (n.data LIKE '%buyer-contact%' OR n.data LIKE '%seller-contact%') GROUP BY p.id ORDER BY MAX(n.datecreated) ASC，AS DATE_FORMAT(FROM_UNIXTIME(MAX( n.datecreated WHERE n.data LIKE '%seller-%' )), '%d-%m-%Y') AS `Last Buyer Contact Note;）等？

Answer 1

您可以在最大函数中放置IF以获取特定值的最大值。

DATE_FORMAT(FROM_UNIXTIME(MAX(IF(n.data LIKE '%buyer-contact%',n.datecreated,NULL))), '%d-%m-%Y') AS `Last Buyer Contact Note`
DATE_FORMAT(FROM_UNIXTIME(MAX(IF(n.data LIKE '%seller-contact%',n.datecreated,NULL))), '%d-%m-%Y') AS `Last Seller Contact Note`

添加这些不应该影响原始查询的性能。

对于WHERE子句的两个单独结果，如何从单个列中的单个列中获取最新的两个日期？

1 个答案: