This field cannot be summarized crystal report error - crystal-reports

Question

I've got the problem about crystal report. I've created one formula field called PAT_DEP and formula is as follow.
Local NUMBERVAR PAT_DEP_AMT := 0;
IF NextIsNull({MYOBJ.PAT_DEPOSIT}) = TRUE THEN
(
IF {MYOBJ.PAT_DEPOSIT} = PREVIOUS({MYOBJ.PAT_DEPOSIT}) THEN
(
PAT_DEP_AMT := 0;
)
ELSE
(
PAT_DEP_AMT := {MYOBJ.PAT_DEPOSIT};
);
)
ELSE
(
IF PREVIOUS({MYOBJ.PAT_DEPOSIT}) = NEXT({MYOBJ.PAT_DEPOSIT}) THEN
(
PAT_DEP_AMT := ToNumber(0);
)
ELSE
(
PAT_DEP_AMT := {MYOBJ.PAT_DEPOSIT};
);
)
Then I've created another formula field called TOT_PAT_DEP and formula is as follow like summarized above formula field.
TOTAL_PAT_DEP := SUM(#PAT_DEP)
But got crystal report error This field cannot be summarized crystal report error. Please help me how come I got this error.

Answer 1

Based on your explanation and formula, it looks like you have a one-to-many relationship which is causing you some difficulty. Let's take an example:
Order Table
Order #, Total, Paid
Order Items Table
Order #, Line #, Description
When you join the two tables you can no longer sum the total/paid columns because they will be multiplied by the number of order lines.
The way to overcome this is to create a group using the key. In my example you would group on Order #. You can then create a running total to sum the total/paid columns but will only evaluate on the change of your Order # group.
Does that make sense?