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Tip of the Day
Language: Relational Databases
Expertise: Beginner
Dec 23, 1997

Calculating the Records

Question:
Can you help me to get a calculated value from many records? A dataset(Paradox table) that I use has an Integer field which is used to put minutes value. How do I add up the value of these fields on many records? In other words, I want to calculate same fields for multiple records in one dataset. I am using DBGrid, and this dataset is a detail table for a master. Thank you. Stan

Answer:
There are two ways to do this: 1) You can drop a TQuery on your form and set it up to run at runtime to sum that field like so:

SELECT Sum(IntField) as IntFieldSum
FROM "MyTable.DB"
Then in the OnCalcFields method for the DBGrid, you can just set the value to
Query1.FieldByName('IntFieldSum).AsInteger;
2) The other way is to scan through the table and do an incremental add. Notice that I didn't put the query in the OnCalcFields method. This is because it would execute everytime you entered a record or made a change - not good. The second method is NOT recommended, especially if you have a lot of records in the table.
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