Mysql case not working

Question

SELECT 
     SQL_CALC_FOUND_ROWS a.* , 
     zn.`name` AS zone_name, 
     c.`name` AS carrier_name, 
     CASE type 
       WHEN type=1 THEN \'General day\' 
       ELS         


        

Answer 1

When you put column name after CASE, you shouldn't use WHEN column = value, just use WHEN value, because it automatically compares the column to each value in the WHEN clauses.

CASE type
    WHEN 1 THEN 'General day'
    ELSE 'Special date'
END AS type_changed,
CASE week_day 
   WHEN -1 THEN 'notset' 
   WHEN 1 THEN 'monday' 
   WHEN 2 THEN 'tuesday' 
   WHEN 3 THEN 'wednesday' 
   WHEN 4 THEN 'thursday' 
   WHEN 5 THEN 'friday' 
   WHEN 6 THEN 'saturday' 
   WHEN 7 THEN 'sunday' 
END AS week_day_mod , 

When you do both, you're testing week_day = (week_day = -1), week_day = (week_day = 1), etc. It works on Monday because 1 = (1 = 1) is equivalent to 1 = 1, which is true; but on Tuesday, it's 2 = (2 = 2), which is equivalent to 2 = 1, which is false.