1.问题产生

$teacherIds = \app\model\Follow::where('shop_id', '=', 18)
    ->field('MAX(id) as id')
    ->group('member_id')
    ->order('id', 'desc')
    ->column('id');

此处生成的sql如下，可以看到max(id)已经没了

SELECT `id` FROM `sat_follow` WHERE ( `shop_id` = 18 ) AND `sat_follow`.`delete_time` IS NULL GROUP BY `member_id` ORDER BY `id` DESC

2.问题解决

$teacherIds = \app\model\Follow::where('shop_id', '=', 18)
    ->group('member_id')
    ->order('id', 'desc')
    ->column('MAX(id) as id');

3.思路

1.把column换成select

$teacherIds = \app\model\Follow::where('shop_id', '=', 18)
    ->field('MAX(id) as id')
    ->group('member_id')
    ->order('id', 'desc')
    ->select();

生成的sql是

SELECT MAX(id) as id FROM `sat_follow` WHERE ( `shop_id` = 18 ) AND `sat_follow`.`delete_time` IS NULL GROUP BY `member_id` ORDER BY `id` DESC

2.可以看到是column影响的，大胆推测column有自己的限定字段逻辑

$teacherIds = \app\model\Follow::where('shop_id', '=', 18)
    ->group('member_id')
    ->order('id', 'desc')
    ->column('MAX(id) as id');

4.原因

//1.vendor\topthink\think-orm\src\db\BaseQuery

//2.connection–这个是数据库构造对象(第一行的result已经把column处理完了)

//3.interface是集成不是实际处理代码的

//4.实际处理的是继承interface的类

//5.用的是mysql所以vendor\topthink\think-orm\src\db\PDOConnection的column方法