SQL/using_NULL.sql at master · muhenge/SQL · GitHub

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SELECT name
FROM teacher
WHERE dept IS NULL

SELECT teacher.name, dept.name
 FROM teacher INNER JOIN dept
           ON (teacher.dept=dept.id)


SELECT teacher.name, dept.name
FROM teacher
LEFT JOIN dept ON (teacher.dept=dept.id)

SELECT teacher.name, dept.name
FROM teacher
RIGHT JOIN dept ON (teacher.dept=dept.id)


SELECT name, COALESCE(mobile,'07986 444 2266')
FROM teacher

SELECT teacher.name, COALESCE(dept.name,'None')
FROM teacher LEFT JOIN dept
ON teacher.dept=dept.id


SELECT COUNT(teacher.name), COUNT(mobile)
FROM teacher

SELECT dept.name, COUNT(teacher.name)
FROM teacher RIGHT JOIN dept
ON teacher.dept=dept.id
GROUP BY dept.name

SELECT name, CASE WHEN dept IN (1,2)
THEN 'Sci'
ELSE 'Art' END
FROM teacher

SELECT name, CASE WHEN dept IN (1,2)
  THEN 'Sci'
  WHEN dept = 3
  THEN 'Art'
  ELSE 'None' END
  FROM teacher