正确使用MySQL表上的连接

Question

原始表如下

operation   processId   errcode
trade            1        200
trade            2        102
trade            3        200
trade            4        200
trade            5        107
trade            6        107
trade            7        200
trade            8        101
trade            9        102
trade           10        200
trade           11        107
bind            17        200
trade           12        200
bind            21        200
validate         4        200
validate         7        201
validate        10        201
validate        17        209
validate        21        207
validate        12        202
passset          1        307
passset          3        308

我想得到如下结果

operation   errcode num
trade         102   2
trade         107   3
trade         200   6
pass          200   1
pass          201   2
pass          202   1
pass          307   1
pass          308   2

validate和passset都将被视为相同的操作名称pass，它们的processId必须与交易相同，我认为join是必须的。我可以使用union并多次加入以获得结果。

我可以用一种优雅的方式得到结果吗？

Answer 1

使用CASE和GROUP BY

with data as
(
   select case when operation = 'validate' or operation = 'passset' 
          then 'pass' 
          else operation end operation,
          errcode
   from your_table
)
select operation, errcode, count(*)
from data
where operation = 'trade'
group by operation, errcode
union all
select d1.operation, d1.errcode, count(*)
from data d1
join data d2 on d1.processId = d2.processId
where d2.operation = 'trade' and d1.operation = 'pass'
group by d1.operation, d1.errcode