using CASE expression in the WHERE clause and BETWEEN operator

Question

I'm trying to fetch some rows from my table based on some condition as follow:

SELECT * FROM MyTable WHERE Date BETWEEN 
CASE dayofweek(curdate())
when 1 then curdate() AND adddate(curdate(), interval 6 day)
when 2 then subdate(curdate(), interval 1 day) AND adddate(curdate(), interval 5 day)
when 3 then subdate(curdate(), interval 2 day) AND adddate(curdate(), interval 4 day)
when 4 then subdate(curdate(), interval 3 day) AND adddate(curdate(), interval 3 day)
when 5 then subdate(curdate(), interval 4 day) AND adddate(curdate(), interval 2 day)
when 6 then subdate(curdate(), interval 5 day) AND adddate(curdate(), interval 1 day)
when 7 then subdate(curdate(), interval 6 day) AND curdate()
END

but for some reason it doesn't work. it gives me a syntax error instead. how should I accomplish something like this?

Answer 1

Try this instead,

SELECT * 
FROM MyTable 
WHERE  1 = 
    CASE dayofweek(curdate())
        when 1 then Date BETWEEN curdate() AND adddate(curdate(), interval 6 day)
        when 2 then Date BETWEEN subdate(curdate(), interval 1 day) AND adddate(curdate(), interval 5 day)
        when 3 then Date BETWEEN subdate(curdate(), interval 2 day) AND adddate(curdate(), interval 4 day)
        when 4 then Date BETWEEN subdate(curdate(), interval 3 day) AND adddate(curdate(), interval 3 day)
        when 5 then Date BETWEEN subdate(curdate(), interval 4 day) AND adddate(curdate(), interval 2 day)
        when 6 then Date BETWEEN subdate(curdate(), interval 5 day) AND adddate(curdate(), interval 1 day)
        when 7 then Date BETWEEN subdate(curdate(), interval 6 day) AND curdate()
    END

The CASE() statement ,in this scenario, will only return two possible values: 1 and 0 .

Answer 2

A CASE returns a value , not an expression . You must repeat the CASE statement for each side of the BETWEEN:

SELECT * FROM MyTable
WHERE Date BETWEEN 
  CASE dayofweek(curdate())
    when 1 then curdate()
    when 2 then subdate(curdate(), interval 1 day)
    ... etc
  END
AND -- this is the "AND" for the BETWEEN values
  CASE dayofweek(curdate())
  when 1 then adddate(curdate(), interval 6 day)
  when 2 then adddate(curdate(), interval 5 day)
  ... etc
END