MySQL的支點與多個計數

Question

這是我的MySQL表的快照：

是否可以編寫一個查詢得到像這樣的輸出數據透視表...

Answer 1

您可以使用CASE聲明來調整您的表。

SELECT url_host, 
     COUNT(CASE WHEN post_ID = -1 THEN 1 ELSE NULL END) Negative_One, 
     COUNT(CASE WHEN post_ID = 0 THEN 1 ELSE NULL END) Zero, 
     COUNT(CASE WHEN post_ID > 0 THEN 1 ELSE NULL END) Greater_Zero 
FROM tableName 
GROUP BY url_host 

SQLFiddle Demo

Answer 2

如何像

SELECT url_host, 
    SUM(CASE WHEN post_id = -1 THEN 1 ELSE 0 END) as post_id_minus1, 
    SUM(CASE WHEN post_id = 0 THEN 1 ELSE 0 END) as post_id_0, 
    etc... 
FROM YOUR_TABLE 
GROUP BY url_host