Question

我有一个包含新闻项的表，我有另一个表media_types，我想创建一个简单的查询，读取media_types表并计算每个记录的news_items存在。

结果将变成我将用于图表的json响应，这是我的SQL语句

SELECT
  gc.country AS "country"
, COUNT(*) AS "online"
FROM default_news_items AS ni
JOIN default_news_item_country AS nic ON (nic.id = ni.country)
JOIN default_country AS c ON (nic.country = c.id)
JOIN default_geo_country AS gc ON (gc.id = c.geo_country)
LEFT JOIN default_medias ON (m.id = ni.media)
WHERE TRUE
  AND ni.deleted = 0
  AND ni.date_item > '2013-10-23'
  AND ni.date_item < '2013-10-29'
AND gc.country <> 'unknown'
AND m.media_type = '14'
GROUP BY gc.country
ORDER BY `online` desc LIMIT 10

这是我从mysql响应中创建的json响应

   [
     {"country":"New Zealand","online":"7"},
     {"country":"Switzerland","online":"1"}
   ]

如何将打印和社交数据添加到我的输出中

我希望json回复看起来像这样

   [
     {"country":"New Zealand","online":"7", "social":"17", "print":"2"},
     {"country":"Switzerland","online":"1", "social":"7", "print":"1"}
   ]

我可以使用select语句中的count (*)来执行类似这样的操作吗

COUNT( * ) as online, COUNT( * ) as social, COUNT( * ) as print

是否可以或者我必须做几个SQL语句来获取我正在寻找的数据？

Answer 1

这是一般结构：

SELECT default_geo_country.country as country,
       SUM(default_medias.media_type = 14) as online,
       SUM(default_medias.media_type = XX) as social,
       SUM(default_medias.media_type = YY) as print
FROM ...
JOIN ...
WHERE ...
GROUP BY country

Answer 2

我认为你想要条件聚合。但是，您的问题仅显示在线媒体类型。

使用表别名并删除后引号，您的查询将更具可读性。此外，如果media_type是一个整数，那么你不应该用单引号括起用于比较的常量 - 对于一个，我发现将字符串常量与整数列进行比较会产生误导。

我怀疑这是你想去的方式。在. . .所在的位置，您希望填写其他媒体类型的计数。

SELECT default_geo_country.country as country,
       sum(media_type = '14') as online,           
       sum(default_medias.media_type = XX) as social,
       sum(default_medias.media_type = YY) as print
       . . . 
FROM default_news_items ni JOIN
     default_news_item_country nic
     ON nic.id = ni.country JOIN
     default_country dc 
     ON nic.country = dc.id JOIN
     default_geo_country gc
     ON gc.id = dc.geo_country LEFT JOIN
     default_medias dm
     ON dm.id = dni.media
WHERE ni.deleted = '0' 
 AND ni.date_item > '2013-10-23' 
 AND ni.date_item < '2013-10-29' 
 AND gc.country <> 'unknown' 
GROUP BY gc.country
ORDER BY online desc
LIMIT 10

MySQL：如何通过连接表计算文章数量

2 个答案: