如何计算 MySQL 中逗号分隔字符串中 substring 的出现次数

Question

假设我选择了这样的记录

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

除了上面的记录，我还想得到groupedStatus字符串中每个substring的出现，

例如，在第一行中，出现如下：

收到：3 接受：3 丢弃：3

原始表架构

表格1

ID int

表 2：

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

我正在使用以下查询选择上述记录

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

您可以使用条件聚合来执行此操作，如下所示：

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