情景:我想创建一个查询,该查询可以返回来自同一列但标准不同的两个或多个字段,以便我可以对数据进行计数。
SQL:
SELECT
FROM_UNIXTIME(news_date, '%Y-%m-%d') AS `DATE`,
COUNT(news_slant=1) AS `Neutral`,
COUNT(news_slant=2) AS `Positive`,
COUNT(news_slant=3) AS `Negative`
FROM tbl_news
GROUP BY `news_date`
ORDER BY `news_date`
答案 0 :(得分:1)
在case
内使用count
:
SELECT
FROM_UNIXTIME(news_date, '%Y-%m-%d') AS `DATE`,
COUNT(case news_slant when 1 then 1 else null end) AS `Neutral`,
COUNT(case news_slant when 2 then 1 else null end) AS `Positive`,
COUNT(case news_slant when 3 then 1 else null end) AS `Negative`
FROM tbl_news
GROUP BY `news_date`
ORDER BY `news_date`
答案 1 :(得分:1)
使用案例陈述:
SELECT FROM_UNIXTIME(news_date, '%Y-%m-%d') AS `DATE`,
COUNT(CASE WHEN news_slant=1 THEN 1 ELSE null END) AS Neutral,
COUNT(CASE WHEN news_slant=2 THEN 1 ELSE null END) AS Positive,
COUNT(CASE WHEN news_slant=3 THEN 1 ELSE null END) AS Negative ,
FROM MyTable
GROUP BY news_date
ORDER BY news_date
答案 2 :(得分:0)
您可以使用标准IF
子句。 COUNT()
只计算非空值。
SELECT
FROM_UNIXTIME(news_date, '%Y-%m-%d') AS DATE,
COUNT(IF(news_slant=1,1,NULL)) AS Neutral,
COUNT(IF(news_slant=2,1,NULL)) AS Positive,
COUNT(IF(news_slant=3,1,NULL)) AS Negative
FROM tbl_news
GROUP BY news_date
ORDER BY news_date