MySQL group data, mysql Group

MySQL group data, mysql Group
For Grouping comprehension groups, see the next example. First, we print the products table as follows:

From the table above, we can see that each vendor has several products. How can we count the number of products in each vendor at a time? You can use group by here, as shown below:

If you do not use group by, the result is the number of rows in the statistics:

Grouping and filtering, that is, filtering the data after multi-statistics. In the example above, the statistics show that each vendor has multiple products, HAVING can be used to filter out more than three vendors:


The WHERE statement can be used together with the HAVING statement. If you need to find out, there are two or more products with a price greater than 10:


Query all data by mysql Group

Grouping SQL statement: select * from table group by ask_id
There should be problems with your test data. They are all the same.
 
Mysql group statistics

SELECT sum (ifnull (t2.total, 0), t1.flag
From B t1
Left join A t2 on t1.id = t2.flag
Group by t1.flag