如何在 mysql 语句中创建多个计数

Question

我在 mysql 语句中计算超过 2 个计数时遇到了一些麻烦。

我的count(b.entry_id) as totalbooking 不起作用。我做错了什么？语句设置也正确吗？

我就是这样尝试的：

"SELECT 
    t.restaurant_id as restaurant_id, ct.title as title, 
    count(DISTINCT t.cardid) as totalmembers, 
    count(t.restaurant_id) as totaltransactions, 
    count(b.entry_id) as totalbooking
    from transactions as t   
    inner join exp_menucard_booking as b on (t.restaurant_id = b.entry_id)
    inner join exp_channel_titles as ct on (t.restaurant_id = ct.entry_id)
    inner JOIN exp_channel_data as cd on (ct.entry_id = cd.entry_id)
    where t.cardid != 88888888 and ct.status = 'open'
    group by t.restaurant_id
    order by ct.title asc";

Answer 1

使用此模式计算总行集的子集：

sum( case when ColumnToBeTested = trueCondition then 1 else 0 end) as SubCount