Question

I am trying to select 1 of 2 rate columns from a table based on the day of the week that is being searched. I am attempting to use two tables for this query: a calendar table (table name=calendar, column name=caldates) which is strictly a list of dates where each row is a date between 2012-06-30 and 2014-05-31. I also have another table (table name=rates) that has 4 columns: start_date, end_date, weekday_rate, and weekend_rate.

Start_date      end_date     weekday_rate     weekend_rate
"2012-05-01"  "2012-06-30"        69              150
"2012-07-01"  "2012-08-31"        74              200
"2012-09-01"  "2012-11-14"        75              210
"2012-11-15"  "2013-01-31"        90              150

When a query is performed, the system needs to look up the correct rate. Right now my query looks like this:

SELECT  
    CASE cast(extract(dow from caldates) as int)
    WHEN '0'  then (select weekday_rate from rates)
    WHEN '1'  then (select weekday_rate from rates)
    WHEN '2'  then (select weekday_rate from rates)
    WHEN '3'  then (select weekday_rate from rates)
    WHEN '4'  then (select weekday_rate from rates)
    WHEN '5'  then (select weekend_rate from rates)
    When '6'  then (select weekend_rate from rates)
    End AS the_date_rate
FROM calendar WHERE caldates >= '2012-08-30' and  caldates <=  '2012-09-04' ;

When I run the query, I receive the error “ERROR: more than one row returned by a subquery used as an expression. “

I would like the output to display the range of dates as well as the rate associated with the date. The above example would look something like

caldates        the_date_rate
2012-08-30           74
2012-08-31           200
2012-09-01           210
2012-09-02           75
2012-09-03           75
2012-09-04           75

Any ideas?

Answer 1

This would be sufficient (also see if you really need quotes around the date-of-week value after when clause):

SELECT  
    CASE 
        WHEN cast(extract(dow from caldates) as int) < 6  then weekday_rate
        ELSE weekend_rate
    End AS the_date_rate
FROM 
    calendar 
WHERE 
    caldates >= '2012-08-30' and  caldates <=  '2012-09-04' ;