How to assign the result of a query to a variable

[kjwageto]

I have a data set that's populated from data set rows in instances of group templates. The number of rows in the data set varies from project to project. I'd like to sum each field/column of the data set and assign each sum to a variable.

I've tried several approaches but I can't quite figure it out. I think I've narrowed it down to using ST logic to query the data set and assign the results to variables.

Here's my sandbox code but I'm getting "Compile error: at line: 19, column: 21; invalid value of type STRUCT, REAL expected".

TYPE
   SumResult: STRUCT
      Value: REAL;
   END_STRUCT;
END_TYPE

PROGRAM TypeSum

VAR NOCACHE
   TotalA AT %S(SELECT SUM(FieldA) AS "Value" FROM DATASET): RESULTSET OF SumResult;
   TotalB AT %S(SELECT SUM(FieldB) AS "Value" FROM DATASET): RESULTSET OF SumResult;
END_VAR

VAR
   SumA AT %M(.TypeATotal): REAL;
   SumB AT %M(.TypeBTotal): REAL;
END_VAR

SumA := TotalA.Value;
SumB := TotalB.Value;

END_PROGRAM

[AndrewScott · Accepted solution]

The two SQL queries are only selecting a single database field so you don't need a STRUCT for the result set:

VAR NOCACHE
   TotalA AT %S(SELECT SUM(FieldA) AS "Value" FROM DATASET): RESULTSET OF REAL;
   TotalB AT %S(SELECT SUM(FieldB) AS "Value" FROM DATASET): RESULTSET OF REAL;
END_VAR

[kjwageto]

Ok... that did confuse me. I tried changing it to DATABASE_OBJECT but basically had similar results. I deleted the TYPE logic and changed it to resultset of REAL and then "Compile... Success". I check the variable values and it looks correct. Thank you for the assistance!