Question

I have resultset like –

Id     var_name    var_value
1      min_points     20
2      max_points     120
3      avg_points     50
4      total_points   320

Here is a query I have tried to write –

select 
         @min_points =case
            when var_name='min_points' then var_value
        end,
        @max_points=case
            when var_name='max_points' then var_value
        end,
        @avg_points=case
            when var_name='avg_points' then var_value
        end,
        @total_points= case  
            when var_name='total_points' then var_value
        end
    from 
        **joined multiple tables**

But the above query does not work and I can understand why..but can anyone help me write a query that will basically help me store all the four var_values in the four variables I have by checking the var_names ?

Answer 1

You need to get the result set into a single row to avoid assigning to the same variables 4 different times. As it stands for each row in the result set the variables are being assigned which means that after the assignment 3 of them will not meet the condition and be NULL and 1 will be NOT NULL.

select 
         @min_points =max(case
            when var_name='min_points' then var_value
        end),
        @max_points=max(case
            when var_name='max_points' then var_value
        end),
        @avg_points=max(case
            when var_name='avg_points' then var_value
        end),
        @total_points= max(case  
            when var_name='total_points' then var_value
        end)
    from 
        **joined multiple tables**

Or alternatively you could keep the multiple assignments but just reassign the same value back to the variable if the row being processed is not the row of interest.

   @min_points = CASE
                   WHEN var_name = 'min_points' THEN var_value
                   ELSE @min_points
                 END