php - MySQL UNION 查询分离

Question

我有这个使用 UNION 的查询:

$this->db->query('
        SELECT DISTINCT users.user_pic, users.id, users.username, contacts.accepted 
        FROM users
        LEFT JOIN contacts ON users.id = contacts.user_1
        WHERE contacts.user_2 = ' . $this->session->userdata('user_id') . '
        UNION DISTINCT
        SELECT DISTINCT users.user_pic, users.id, users.username, contacts.accepted 
        FROM users 
        LEFT JOIN contacts ON users.id = contacts.user_2
        WHERE user_1 = ' . $this->session->userdata('user_id')
);

有没有办法查看 session “user_id”是否在 contacts.user_1 或 contacts.user_2 中遇到？也许通过更改查询，或者我是否可以在 View 中使用一些 if 语句？

提前致谢

乔治

Answer 1

是的，你可以添加另一个字段来选择，你可以像 (1,2) 这样识别

$this->db->query('
        SELECT 1 as table_id,DISTINCT users.user_pic, users.id, users.username, contacts.accepted 
        FROM users
        LEFT JOIN contacts ON users.id = contacts.user_1
        WHERE contacts.user_2 = ' . $this->session->userdata('user_id') . '
        UNION DISTINCT
        SELECT 2 as table_id,DISTINCT users.user_pic, users.id, users.username, contacts.accepted 
        FROM users 
        LEFT JOIN contacts ON users.id = contacts.user_2
        WHERE user_1 = ' . $this->session->userdata('user_id')
);