SELECT查询，显示每个记录的名称和实例数

Question

Is it possible to write a SELECT query that displays the name of each record once and the count of how many instances of that record there are for certain criteria?

For example, If I have a table with the following records:

How can I get the SELECT query to display the following:

Answer 1

You can use conditional aggregation:

select customer,
       sum( status = 'Disposed' ) as num_disposed,
       sum( status = 'Transported' ) as num_transported
from t
group by customer;

MySQL treats boolean expressions like integers in a numeric context, with 0 for false and 1 for true. So, just adding up the boolean is a simple way to count the number of rows that match the condition.

Answer 2

you can use a group by on case ansum for case

 select customer, sum(case when status ='disposed' then 1 else 0 end) count_disposed 
        sum(case when status ='trasposed' then 1 else 0 end) count_trasposed 
from my_table 
group by customer