أهداف الدرس
- أن تجمع بيانات من جدولين.
- أن تعدّ وتجمّع.
SQL
SELECT d.name AS department,
COUNT(e.id) AS staff
FROM departments d
LEFT JOIN employees e ON e.department_id = d.id
GROUP BY d.name
ORDER BY staff DESC;LEFT JOIN هنا يُظهر القسم الذي لا موظفين فيه بعدد 0، وINNER JOIN كان سيُخفيه.
تمرين
اعرض الأقسام التي فيها أكثر من عشرة موظفين.
الإجابة
أضف HAVING COUNT(e.id) > 10 بعد GROUP BY.
Lesson goals
- Combine data from two tables.
- Count and group.
SQL
SELECT d.name AS department,
COUNT(e.id) AS staff
FROM departments d
LEFT JOIN employees e ON e.department_id = d.id
GROUP BY d.name
ORDER BY staff DESC;The LEFT JOIN shows a department with no staff as 0; an INNER JOIN would hide it.
Exercise
Show departments with more than ten staff.
Answer
Add HAVING COUNT(e.id) > 10 after GROUP BY.
التعليقات / Comments
لا تعليقات بعد. كن أول من يسأل. / No comments yet. Be the first to ask.