Use an arithmetic function

The following query adds the values of two tags from the WideHistory table.

SELECT * FROM OpenQuery(INSQL,'

SELECT DateTime, ReactLevel, ProdLevel, "Sum" = ReactLevel+Prodlevel

FROM WideHistory

WHERE DateTime > "2001-02-28 18:56"

AND DateTime < "2001-02-28 19:00"

AND wwRetrievalMode = "Cyclic"

')

The results are:

If you use a math operator, such as plus (+), minus (-), multiply (*), or divide (/), you will need to add a blank space in front of and after the operator. For example, "Value - 2" instead of "Value-2".