如何计算 MySQL 中逗号分隔字符串中 substring 的出现次数

Question

Let's say I have selected records like this

+----+-------------------------------------------------------------------------------------
| id | groupedStatus                                                                      |
+----+-------------------------------------------------------------------------------------
| 1 | received,accepted,discarded,discarded,accepted,discarded,accepted,received,received |
| 2 | accepted,discarded,received,received,received,received,received                     |          
+----+-------------------------------------------------------------------------------------

Along with the above records, I also want to get the occurrence of each substring in the groupedStatus string,

for example, in the first row, the occurrences are as follows:

received: 3 accepted: 3 discarded: 3

Original Table Schema

Table1

ID int

Table 2:

ID
Table1ID
Status enum('received','accepted','discarded') 

I am selecting above records using the following query

select t1.id, group_concat(t2.status) as groupedStatus from Table1 t1 inner join Table2 t2 on t1.id=t2.table1ID group by t1.id

Answer 1

You can do this with conditional aggregation, like so:

select 
    t1.id, 
    sum(t2.status = 'received')  as received,
    sum(t2.status = 'accepted')  as accepted,
    sum(t2.status = 'discarded') as discarded,
    group_concat(t2.status) as groupedStatus 
from table1 t1 
inner join table2 t2 on t1.id = t2.table1ID 
group by t1.id