查询在多个条件下从表1连接表2中选择多个计数

Question

我有一些问题如何从1个表中查询具有不同条件的多个计数。

SELECT COUNT(*) FROM account_holder
INNER JOIN vehicle 
ON account_holder.`id`= vehicle.`accholder_id`
WHERE vehicle.`class_code`= 'BM' AND (vehicle.`roadtax_expired` > CURDATE()) 
AND (vehicle.`block_flag`='N') AND (vehicle.`is_blacklist`='N')

场景：我想用不同的代码计算表格车辆中的class_code。例如，我的查询只计算BM的代码，但是如何在一个查询中计算其他class_code？

其他不同的class_code：BL，CA，CE ......

Answer 1

您需要GROUP BY子句来计算每个class_code。

SELECT vehicle.`class_code`, COUNT(*) 
FROM account_holder
     INNER JOIN vehicle 
        ON account_holder.`id`= vehicle.`accholder_id`
WHERE (vehicle.`roadtax_expired` > CURDATE()) 
       AND (vehicle.`block_flag`='N') 
       AND (vehicle.`is_blacklist`='N')
GROUP BY vehicle.`class_code`

Answer 2

您可以尝试使用group by，

SELECT COUNT(vehicle.`class_code`) as class_code count FROM  account_holder
INNER JOIN vehicle 
ON account_holder.`id`= vehicle.`accholder_id`
WHERE (vehicle.`roadtax_expired` > CURDATE()) 
AND (vehicle.`block_flag`='N') AND (vehicle.`is_blacklist`='N') group   by vehicle.`class_code`