MYSQL-如何计算每月出现的次数

Question

I have a table with a varchar column and a datetime column that I want to get some counts from:

CREATE TABLE `appointment` (
  `appointmentId` int(10) NOT NULL AUTO_INCREMENT,
  `cid` int(10) NOT NULL,
  `title` varchar(255) NOT NULL,
  `description` text NOT NULL,
  `location` text NOT NULL,
  `contact` text NOT NULL,
  `start` datetime NOT NULL,
  PRIMARY KEY (`appointmentId`));

Some values:

INSERT INTO `appointment` (`cid`, `title`, `description`, `location`, `contact`, `start`) 
VALUES 
('1', 'text1', ' ', ' ', ' ', '2017-07-21 16:00'),
('2', 'text1', ' ', ' ', ' ', '2017-08-21 16:00'),
('1', 'text1', ' ', ' ', ' ', '2017-09-21 16:00'),
('1', 'text1', ' ', ' ', ' ', '2017-09-21 16:00'),
('3', 'text2', ' ', ' ', ' ', '2017-07-21 16:00'),
('1', 'text3', ' ', ' ', ' ', '2017-07-21 16:00'),
('1', 'text4', ' ', ' ', ' ', '2017-07-21 16:00'),
('5', 'text5', ' ', ' ', ' ', '2017-07-21 16:00'),
('1', 'text1', ' ', ' ', ' ', '2017-07-21 16:00'),
('1', 'text1', ' ', ' ', ' ', '2017-07-21 16:00'),
('1', 'text3', ' ', ' ', ' ', '2017-07-21 16:00');

What I want to accomplish is to get a count of the occurrences of a 'title' on a monthly basis. Something like this:

Month       | title | count 
--------------------------- 
July        | text1  | 3 
August      | text1  | 1  
September   | text1  | 2 
July        | text2  | 1 
etc...

I have gotten as far as

SELECT  MONTHNAME(start) AS 'MONTH',
    title AS 'TITLE',
    count(title) AS 'COUNT'
FROM appointment
GROUP BY TITLE

But, that is grouping all of text1 into a total count on the first month of occurrence. So, for the example above it is showing: 'July | text1 | 6'

I've tried several variations on that query, but I'm clearly missing something.

Can someone explain: a) why is it aggregating all of those into one month? and b) how to get the query to produce the results I want?

Answer 1

Not sure if you tried this or not but you need to group by month like:

SELECT  MONTH(start) AS MONTH,
    title AS TITLE,
    count(title) AS COUNT
FROM appointment
GROUP BY title,MONTH(start);

Plus why do you need quotes after AS ...?

Answer 2

You need to group by monthname(Start) as well so GROUP BY Title, MonthName(start) .

The reason why you're seeing July text1 6 is because all of text1 is being put into July, not just july. Typically any non-aggregated field int eh select should be in the group by. mySQL extends the group by to not thow an error when a non-aggregated field isn't in the group by; whereas oracle, db2, SQL Server Postgresql and others would all throw an error. There is a setting which can be disabled in mySQL which would cause your SQL to error since monthname(start) wasn't in the group by.

https://dev.mysql.com/doc/refman/5.7/en/group-by-handling.html