The case statements are similar to the switch cases like in C/C#. The CASE executes the statement which is logically correct and matches the condition.
Take the following example , that the you want to select a particular teachername from the list through teacherId column, from the following table StudentDetail :
Select studentid, studentname, teacherid, teachername from StudentDetail
Using the case expression :
SELECT studentid, studentname, teacherid, teachername
CASE teacherid
WHEN 1 THEN ‘Teacher1’
WHEN 2 THEN ‘Teacher2’
WHEN 3 THEN ‘Teacher3’
WHEN 4 THEN ‘Teacher4’
WHEN 5 THEN ‘Teacher5’
WHEN 6 THEN ‘Teacher6’
WHEN 7 THEN ‘Teacher7’
WHEN 8 THEN ‘Teacher8’
ELSE ‘Unknown’
END
FROM StudentDetail order by studentid
SqlBird 