计算mysql查询中作为别名字段的总和

我试图通过添加两个别名字段的总和来修改查询

原始查询是：

SELECT event_date.meta_value AS 'Event Date'
    , ugm.group_id AS 'Gig ID'
    , p_title.post_title AS 'Client'
    , event_venue.meta_value AS 'Venue'
    , wum_l.meta_value last_name
    , wum_f.meta_value first_name
    , wum_m.meta_value AS 'Miles' 
    , wum_mp.meta_value AS 'Mileage Pay'
    , wum.meta_value  AS 'Gig Pay' 
FROM wp_users wu
INNER JOIN wp_um_groups_members ugm
    ON  ugm.user_id1 = wu.id
LEFT JOIN  wp_usermeta wum
    ON wu.id = wum.user_id
    AND wum.meta_key = CONCAT('um_groups_', ugm.group_id, '_price')   
LEFT JOIN wp_usermeta wum_f
    ON wu.id = wum_f.user_id
    AND wum_f.meta_key = 'first_name'
LEFT JOIN wp_usermeta wum_l
    ON wu.id = wum_l.user_id
    AND wum_l.meta_key = 'last_name'
LEFT JOIN wp_posts p_title
    ON p_title.id = ugm.group_id
LEFT JOIN wp_usermeta wum_m
    ON wu.id = wum_m.user_id
    AND wum_m.meta_key = CONCAT('_um_groups_', ugm.group_id, '_mileage') 
LEFT JOIN wp_usermeta wum_mp
    ON wu.id = wum_mp.user_id
    AND wum_mp.meta_key = CONCAT('um_groups_', ugm.group_id, '_mileage_price')
LEFT JOIN wp_postmeta event_date
    ON event_date.post_id= ugm.group_id    
    AND event_date.meta_key = '_um_groups_event_start'
LEFT JOIN wp_postmeta event_venue
    ON event_venue.post_id= ugm.group_id    
    AND event_venue.meta_key = '_um_groups_event_venue'
 WHERE  STR_TO_DATE(event_date.meta_value, '%Y/%m/%d') BETWEEN STR_TO_DATE('2021/1/01', '%Y-%m-%d') AND STR_TO_DATE('2021/1/15', '%Y-%m-%d') 
AND wum.meta_value IS NOT NULL
ORDER BY wu.display_name  ASC;

我要做的是创建一个名为

Total Pay

的最终别名字段，在该字段中计算每行的

Gig Pay

和

里程支付的总和

我遇到的问题是，我在查询中使用了
SUM
，得到了每个匹配行的总和。我只想要每行的总数

例如，预期输出如下所示：

Event Date  Gig ID  Client      Venue       last_name   first_name  Miles   Mileage Pay Gig Pay Total Pay
2021/01/15  49270   Joe Schmoe  This Event  Doe         Joe         2       120         732     852 

我需要如何修改查询以显示每行总和的新别名字段？
只需添加这两个字段就可以根据需要工作

SELECT event_date.meta_value AS 'Event Date'
    , ugm.group_id AS 'Gig ID'
    , p_title.post_title AS 'Client'
    , event_venue.meta_value AS 'Venue'
    , wum_l.meta_value last_name
    , wum_f.meta_value first_name
    , wum_m.meta_value AS 'Miles' 
    , wum_mp.meta_value AS 'Mileage Pay'
    , wum.meta_value  AS 'Gig Pay'
    , wum_mp.meta_value + wum.meta_value  AS 'Total Pay' 
FROM wp_users wu
INNER JOIN wp_um_groups_members ugm
    ON  ugm.user_id1 = wu.id
LEFT JOIN  wp_usermeta wum
    ON wu.id = wum.user_id
    AND wum.meta_key = CONCAT('um_groups_', ugm.group_id, '_price')   
LEFT JOIN wp_usermeta wum_f
    ON wu.id = wum_f.user_id
    AND wum_f.meta_key = 'first_name'
LEFT JOIN wp_usermeta wum_l
    ON wu.id = wum_l.user_id
    AND wum_l.meta_key = 'last_name'
LEFT JOIN wp_posts p_title
    ON p_title.id = ugm.group_id
LEFT JOIN wp_usermeta wum_m
    ON wu.id = wum_m.user_id
    AND wum_m.meta_key = CONCAT('_um_groups_', ugm.group_id, '_mileage') 
LEFT JOIN wp_usermeta wum_mp
    ON wu.id = wum_mp.user_id
    AND wum_mp.meta_key = CONCAT('um_groups_', ugm.group_id, '_mileage_price')
LEFT JOIN wp_postmeta event_date
    ON event_date.post_id= ugm.group_id    
    AND event_date.meta_key = '_um_groups_event_start'
LEFT JOIN wp_postmeta event_venue
    ON event_venue.post_id= ugm.group_id    
    AND event_venue.meta_key = '_um_groups_event_venue'
 WHERE  STR_TO_DATE(event_date.meta_value, '%Y/%m/%d') BETWEEN STR_TO_DATE('2021/1/01', '%Y-%m-%d') AND STR_TO_DATE('2021/1/15', '%Y-%m-%d') 
AND wum.meta_value IS NOT NULL
ORDER BY wu.display_name  ASC;

这是一个内部连接，您认为
STR\u到日期（'2021/1/15'，'%Y-%m-%d'）
有什么作用？@。我在那里有一个变量$start，当我直接测试查询时，我刚刚替换了它。您认为
STR\u TO\u DATE（变量，'%Y-%m-%d'）
的作用是什么？