在mysql中使用别名计算where条件

您好，正在运行此查询，我想在where条件下用如下case语句检查use

delegationcount

和

sumstatus

select 
    delegation_cycle.delegation_cycle_id as task_id,
    delegation_cycle.delegate_from_id as from_id,
    delegation_cycle.delegate_to_id as to_id,
    delegation_cycle.time_estimate as main_time_estimate,
    delegation_cycle.status as main_task_status,
    delegation_cycle.start_date as main_start_date,
    delegation_cycle.changes,
    DATE(delegation_cycle.delegated_time) as orginal_email_time,
    tasks.task_name,
    tasks.client_id,
    tasks.followup,
    tasks.task_owner,
    tasks.main_due_date,
    tasks.main_priority,
    1 as delegated,
    delegation_user_relation.showinlist,
    users.email as email_from,
    clients.client_name,
    (select 
            count(delegation_cycle_id)
        from
            delegation_cycle
        where
            delegation_cycle.task_id = tasks.task_id
                and delegation_cycle.task_parent = '2') as delegationcount,
    (select 
            sum(status)
        from
            delegation_cycle
        where
            delegation_cycle.task_id = tasks.task_id
                and delegation_cycle.task_parent = '2'
                and delegation_cycle.status = '4') as sumstatus,
    (select 
            count(notes_records_id)
        from
            notes_records
                join
            notes ON notes.notes_id = notes_records.notes_id
        where
            notes_to = '2'
                and notes.task_id = delegation_cycle.task_id) as notescount,
    (select 
            count(notes_records_id)
        from
            notes_records
                join
            notes ON notes.notes_id = notes_records.notes_id
        where
            notes_to = '2'
                and notes.task_id = delegation_cycle.task_id
                and notes_records.read = 0) as unreadnotescount
from
    delegation_cycle
        inner join
    tasks ON tasks.task_id = delegation_cycle.task_id
        inner join
    users ON users.user_id = delegation_cycle.delegate_from_id
        inner join
    clients ON clients.client_id = tasks.client_id
        join
    delegation_user_relation ON delegation_user_relation.delegate_task_id = tasks.task_id
where
    delegation_cycle.delegate_to_id = '2'
        and delegation_cycle.status != 4
        and case
        when
            delegation_cycle.status != 3
        then
            (delegation_user_relation.showinlist = 1
                || delegation_user_relation.showinlist = 2)
                and delegation_user_relation.user_id = '2'

        else delegation_user_relation.user_id = '2'
    end

---

我想在where条件中使用alise名称，但我无法使用此查询，因此我想重新构造此查询，以便在where条件中使用alise名称

您可以在查询中定义临时会话变量，并在where子句中使用相同的变量

 when delegation_cycle.status != 3 && delegationcount*4!=sumstatus then 
(delegation_user_relation.showinlist = 1 || delegation_user_relation.showinlist = 2)  
 and delegation_user_relation.user_id = '2'  else delegation_user_relation.user_id = '2'    
 end

并将新的

when…

条款更改如下：

select 
    delegation_cycle.delegation_cycle_id as task_id,
    delegation_cycle.delegate_from_id as from_id,
    delegation_cycle.delegate_to_id as to_id,
    delegation_cycle.time_estimate as main_time_estimate,
    delegation_cycle.status as main_task_status,
    delegation_cycle.start_date as main_start_date,
    delegation_cycle.changes,
    DATE(delegation_cycle.delegated_time) as orginal_email_time,
    tasks.task_name,
    tasks.client_id,
    tasks.followup,
    tasks.task_owner,
    tasks.main_due_date,
    tasks.main_priority,
    1 as delegated,
    delegation_user_relation.showinlist,
    users.email as email_from,
    clients.client_name,

    @delegationcount:=(select 
            count(delegation_cycle_id)
        from
            delegation_cycle
        where
            delegation_cycle.task_id = tasks.task_id
                and delegation_cycle.task_parent = '2') as delegationcount,

    @sumstatus:=(select 
            sum(status)
        from
            delegation_cycle
        where
            delegation_cycle.task_id = tasks.task_id
                and delegation_cycle.task_parent = '2'
                and delegation_cycle.status = '4') as sumstatus,

    @notescount:=(select 
            count(notes_records_id)
        from
            notes_records
                join
            notes ON notes.notes_id = notes_records.notes_id
        where
            notes_to = '2'
                and notes.task_id = delegation_cycle.task_id) as notescount,

    @unreadnotescount:=(select 
            count(notes_records_id)
        from
            notes_records
                join
            notes ON notes.notes_id = notes_records.notes_id
        where
            notes_to = '2'
                and notes.task_id = delegation_cycle.task_id
                and notes_records.read = 0) as unreadnotescount
from
    delegation_cycle
        inner join
    tasks ON tasks.task_id = delegation_cycle.task_id
        inner join
    users ON users.user_id = delegation_cycle.delegate_from_id
        inner join
    clients ON clients.client_id = tasks.client_id
        join
    delegation_user_relation ON delegation_user_relation.delegate_task_id = tasks.task_id
where
    delegation_cycle.delegate_to_id = '2'
        and delegation_cycle.status != 4
        and case
        when
            delegation_cycle.status != 3
        then
            (delegation_user_relation.showinlist = 1
                || delegation_user_relation.showinlist = 2)
                and delegation_user_relation.user_id = '2'

        else delegation_user_relation.user_id = '2'
    end

---

你能不能说清楚一点，告诉我们你面临什么问题？你看到一个错误了吗？我不会再接近这个了！我想在where条件中使用alise名称，但这对我来说是不可能的，因此我想重新构造此查询以在where条件中使用alise名称。您希望别名是什么？@G one在此处使用委派\u cycle.status！=3&&delegationcount*4=当表1中有10万条记录时，这会导致性能问题。重新计算时间下降了，这很好。2.除非在某些字段上有索引，否则可能会影响。

when 
  delegation_cycle.status != 3 && 
  @delegationcount*4!=@sumstatus then 
    (delegation_user_relation.showinlist = 1 || 
     delegation_user_relation.showinlist = 2
    ) and delegation_user_relation.user_id = '2' 
  else
    delegation_user_relation.user_id = '2'    
end