giá trị cột trong một hàng

Đây là hai phương pháp khác, chỉ để hoàn thiện:

1. SELECT
     p.name,
     MAX(CASE t.phonetype WHEN 'work' THEN t.phoneno END) AS workphone,
     MAX(CASE t.phonetype WHEN 'home' THEN t.phoneno END) AS homephone,
     MAX(CASE t.phonetype WHEN 'mob' THEN t.phoneno END) AS mobilephone
   FROM people p
     INNER JOIN phones t ON p.Id = t.Id
   GROUP BY p.Id, p.Name
   

2. SELECT
     p.name,
     w.phoneno AS workphone,
     h.phoneno AS homephone,
     m.phoneno AS mobilephone
   FROM people p
     LEFT JOIN phones w ON p.Id = w.Id AND w.phonetype = 'work'
     LEFT JOIN phones h ON p.Id = h.Id AND h.phonetype = 'home'
     LEFT JOIN phones m ON p.Id = m.Id AND m.phonetype = 'mob'