MySQL時間段查詢，無數據補0

上一節提到分時間段統計，可是無數據的時候不顯示，而此時我們需要讓他顯示0。

 

首先我們需要建一個時間表。

CREATE TABLE `my_date` (
  `date` date NOT NULL,
  PRIMARY KEY (`date`)
)

並且插入一些數據，具體怎么插入有好多種方法，目的是生成我們需要的時間格式，如下

 

以下就要用到我們的時間表，與我們的數據表進行連接查詢了。呃，中間的1你們可以忽略啊！！你們需要看的只有 t 和 count

mysql> select DATE_FORMAT(md.date,'%Y-%m') t,1,count(*) from my_date md left join article a on DATE_FORMAT(md.date,'%Y-%m') = DATE_FORMAT(a.article_time,'%Y-%m') group by t;

+---------+---+----------+
| t       | 1 | count(*) |
+---------+---+----------+
| 2015-01 | 1 |        1 |
| 2015-02 | 1 |        1 |
| 2015-03 | 1 |        1 |
| 2015-04 | 1 |        1 |
| 2015-05 | 1 |        1 |
| 2015-06 | 1 |        1 |
| 2015-07 | 1 |        1 |
| 2015-08 | 1 |        1 |
| 2015-09 | 1 |        1 |
| 2015-10 | 1 |        1 |
| 2015-11 | 1 |        1 |
| 2015-12 | 1 |        1 |
| 2016-01 | 1 |        1 |
| 2016-02 | 1 |        1 |
| 2016-03 | 1 |        1 |
| 2016-04 | 1 |        1 |
| 2016-05 | 1 |        1 |
| 2016-06 | 1 |        1 |
| 2016-07 | 1 |        1 |
| 2016-08 | 1 |       22 |
| 2016-09 | 1 |       26 |
| 2016-10 | 1 |        3 |
| 2016-11 | 1 |        1 |
| 2016-12 | 1 |        1 |
+---------+---+----------+
24 rows in set

這里出現了一個問題，無數據的字段變成1了，哈哈哈，什么鬼呀，神經病啊。注意，這里的count(*) 代表統計所有的行，你數據表的那一行無數據，可是我們進行left join 獲得的一行不止數據表吧？還有時間表的，時間表那里不為空，是有數據的，所以變成了1。所以我們要把count(*) 變成 count(a.article_id)

mysql> select DATE_FORMAT(md.date,'%Y-%m') t,1,count(a.article_id) from my_date md left join article a on DATE_FORMAT(md.date,'%Y-%m') = DATE_FORMAT(a.article_time,'%Y-%m') group by t;
+---------+---+---------------------+
| t       | 1 | count(a.article_id) |
+---------+---+---------------------+
| 2015-01 | 1 |                   0 |
| 2015-02 | 1 |                   0 |
| 2015-03 | 1 |                   0 |
| 2015-04 | 1 |                   0 |
| 2015-05 | 1 |                   0 |
| 2015-06 | 1 |                   0 |
| 2015-07 | 1 |                   0 |
| 2015-08 | 1 |                   0 |
| 2015-09 | 1 |                   0 |
| 2015-10 | 1 |                   1 |
| 2015-11 | 1 |                   0 |
| 2015-12 | 1 |                   0 |
| 2016-01 | 1 |                   0 |
| 2016-02 | 1 |                   0 |
| 2016-03 | 1 |                   0 |
| 2016-04 | 1 |                   0 |
| 2016-05 | 1 |                   0 |
| 2016-06 | 1 |                   0 |
| 2016-07 | 1 |                   1 |
| 2016-08 | 1 |                  22 |
| 2016-09 | 1 |                  26 |
| 2016-10 | 1 |                   3 |
| 2016-11 | 1 |                   1 |
| 2016-12 | 1 |                   1 |
+---------+---+---------------------+
24 rows in set

到這里我們發現，時間表里面有多少時間就查出多少，如果我時間表里面有1億個那還了得！所以我們要進行限制，比如要查當前年份的每個月數據。

mysql> select DATE_FORMAT(md.date,'%Y-%m') t,1,count(a.article_id) from my_date md left join article a on DATE_FORMAT(md.date,'%Y-%m') = DATE_FORMAT(a.article_time,'%Y-%m') where DATE_FORMAT(md.date,'%Y') = DATE_FORMAT(curdate(),'%Y') group by t;
+---------+---+---------------------+
| t       | 1 | count(a.article_id) |
+---------+---+---------------------+
| 2016-01 | 1 |                   0 |
| 2016-02 | 1 |                   0 |
| 2016-03 | 1 |                   0 |
| 2016-04 | 1 |                   0 |
| 2016-05 | 1 |                   0 |
| 2016-06 | 1 |                   0 |
| 2016-07 | 1 |                   1 |
| 2016-08 | 1 |                  22 |
| 2016-09 | 1 |                  26 |
| 2016-10 | 1 |                   3 |
| 2016-11 | 1 |                   1 |
| 2016-12 | 1 |                   1 |
+---------+---+---------------------+
12 rows in set

如果我們要指定年份呢

mysql> select DATE_FORMAT(md.date,'%Y-%m') t,1,count(a.article_id) from my_date md left join article a on DATE_FORMAT(md.date,'%Y-%m') = DATE_FORMAT(a.article_time,'%Y-%m') where DATE_FORMAT(md.date,'%Y') = '2015' group by t;
+---------+---+---------------------+
| t       | 1 | count(a.article_id) |
+---------+---+---------------------+
| 2015-01 | 1 |                   0 |
| 2015-02 | 1 |                   0 |
| 2015-03 | 1 |                   0 |
| 2015-04 | 1 |                   0 |
| 2015-05 | 1 |                   0 |
| 2015-06 | 1 |                   0 |
| 2015-07 | 1 |                   0 |
| 2015-08 | 1 |                   0 |
| 2015-09 | 1 |                   0 |
| 2015-10 | 1 |                   1 |
| 2015-11 | 1 |                   0 |
| 2015-12 | 1 |                   0 |
+---------+---+---------------------+
12 rows in set

 

那個時間表里面的數據一定要事先生成咯，生成個幾十年就夠用了，公司說不定活不到那個時候呢哈哈哈，好好笑

下面進行一下每年的統計，到這里我時間表加入了2014年的12個月

mysql> select DATE_FORMAT(md.date,'%Y') t,1,count(a.article_id) from my_date md left join article a on DATE_FORMAT(md.date,'%Y-%m') = DATE_FORMAT(a.article_time,'%Y-%m') group by t;
+------+---+---------------------+
| t    | 1 | count(a.article_id) |
+------+---+---------------------+
| 2014 | 1 |                   0 |
| 2015 | 1 |                   1 |
| 2016 | 1 |                  54 |
+------+---+---------------------+
3 rows in set

這個呢，時間表里面有多少年就顯示多少年，我們也可以指定、

mysql> select DATE_FORMAT(md.date,'%Y') t,1,count(a.article_id) from my_date md left join article a on DATE_FORMAT(md.date,'%Y-%m') = DATE_FORMAT(a.article_time,'%Y-%m') where DATE_FORMAT(md.date,'%Y') > '2014' group by t;
+------+---+---------------------+
| t    | 1 | count(a.article_id) |
+------+---+---------------------+
| 2015 | 1 |                   1 |
| 2016 | 1 |                  54 |
+------+---+---------------------+
2 rows in set

mysql> select DATE_FORMAT(md.date,'%Y') t,1,count(a.article_id) from my_date md left join article a on DATE_FORMAT(md.date,'%Y-%m') = DATE_FORMAT(a.article_time,'%Y-%m') where DATE_FORMAT(md.date,'%Y') > '2014' and DATE_FORMAT(md.date,'%Y') < '2016' group by t;
+------+---+---------------------+
| t    | 1 | count(a.article_id) |
+------+---+---------------------+
| 2015 | 1 |                   1 |
+------+---+---------------------+
1 row in set