Question

我的问题是我们做了一个选择，然后，对于每一行，我们运行4个不同的请求SQL（疯狂），因为你可以猜测我们做了很多请求，并且使用它的系统非常慢。

SELECT 
    deal_source.id, 
    deal_source.source_name, 
    deal_source.spider_status, 
    spider.last_success_date
FROM deal_source 
JOIN spider 
ON deal_source.id = spider.deal_source_id

然后，对于此查询的每一行，我们进行：

$total_query = "SELECT count(id) as total
                FROM spider_log 
                WHERE deal_source_id = '$deal_source_id' 
                AND date_format(date_created, '%Y-%m-%d') = '$lastdate' ";

$added_query = "SELECT count(id) as added
                FROM spider_log 
                WHERE deal_source_id = '$deal_source_id' 
                AND action = 'added'  
                AND date_format(date_created, '%Y-%m-%d') = '$lastdate' ";

$extended_query = "SELECT count(id) as extended 
                   FROM spider_log 
                   WHERE deal_source_id = '$deal_source_id' 
                   AND action = 'extended'  
                   AND date_format(date_created, '%Y-%m-%d') = '$lastdate' ";

$duplicate_query = "SELECT count(id) as duplicate 
                    FROM spider_log 
                    WHERE deal_source_id = '$deal_source_id' 
                    AND action = 'duplicate'  
                    AND date_format(date_created, '%Y-%m-%d') = '$lastdate' ";

Answer 1

SELECT   d.id,
         d.source_name,
         d.spider_status,
         s.last_success_date,
         COUNT(l.id) AS total,
         SUM(l.id IS NOT NULL AND l.action='added'    ) AS added,
         SUM(l.id IS NOT NULL AND l.action='extended' ) AS extended,
         SUM(l.id IS NOT NULL AND l.action='duplicate') AS duplicate
FROM     deal_source d
    JOIN spider      s
      ON s.deal_source_id  = d.id
    JOIN spider_log  l
      ON l.deal_source_id  = d.id
      ON l.date_created   >= s.last_success_date
     AND l.date_created   <  s.last_success_date + INTERVAL 1 DAY
GROUP BY d.id

Answer 2

有些观点：

您可以使用EXPLAIN并谨慎添加索引来优化每个查询的效果。
您可以将所有查询组合成一个大查询，这样您就不必通过大量查询来访问数据库。
除了大量的查询之外，date_format(date_created, '%Y-%m-%d') = '$lastdate'是一个性能杀手，因为它将一个函数（DATE_FORMAT()）用于一个列（date_created），因此不能使用任何索引并且该函数被称为thosuand或数百万次（检查多行）。将这些条件（无论它们在您的代码中）更改为：
```
 (  date_created >= DATE('$lastdate') 
AND date_created < DATE('$lastdate') + INTERVAL 1 DAY
 )
```
甚至更好，如果$lastdate是日期，请：
```
 (  date_created >= '$lastdate' 
AND date_created < '$lastdate' + INTERVAL 1 DAY
 )
```
如果date_created是DATE列，则更好：
```
    date_created = '$lastdate' 
```

如何使用MYSQL（每行的子查询）优化这些指令？

2 个答案: