What is DSum used for and what is the syntax?

it's like a subquery shortcut..

rockiroads ,
Does it have to be from a table? Can it be from a query?

Thanks

More info

DSUM is considered a Domain Aggregate function, and it works just like DMAX, DMIN, DLOOKUP, DCOUNT
All these have the same syntax,

If u had a table called Fred and u had field called Credit
And the data was like this

FredID, Credit

1, 10
2, 20
3, 15
4, 10
3, 20

then

DSUM("Credit","Fred") will return 65
DSUM("Credit","Fred","FredID=3") will return 35



This is taken from the online help page

You can use the DSum functions to calculate the sum of a set of values in a specified set of records (a domain (domain: A set of records defined by a table, a query, or an SQL expression. Domain aggregate functions return statistical information about a specific domain or set of records.)). Use the DSum function in Visual Basic, a macro (macro: An action or a set of actions you can use to automate tasks. Macros are recorded in the Visual Basic for Applications programming language.), a query expression, or a calculated control (calculated control: A control used on a form, report, or data access page to display the result of an expression. The result is recalculated each time there is a change in any of the values that the expression is based on.). Variant.

expression.DSum(Expr, Domain, Criteria)

expression   Required. An expression that returns one of the objects in the Applies To list.

Expr  Required String. An expression that identifies the numeric field whose values you want to total. It can be a string expression (string expression: Any expression that evaluates to a sequence of contiguous characters. Elements of the expression can include: a function that returns a string or a string Variant (VarType 8); a string literal, constant, variable, or Variant</.) identifying a field in a table or query, or it can be an expression that performs a calculation on data in that field. In expr, you can include the name of a field in a table, a control on a form, a constant, or a function. If expr includes a function, it can be either built-in or user-defined, but not another domain aggregate or SQL aggregate function.

Domain  Required String. A string expression identifying the set of records that constitutes the domain. It can be a table name or a query name.

Criteria  Optional Variant. An optional string expression used to restrict the range of data on which the DSum function is performed. For example, criteria is often equivalent to the WHERE clause in an SQL expression, without the word WHERE. If criteria is omitted, the DSum function evaluates expr against the entire domain. Any field that is included in criteria must also be a field in domain; otherwise, the DSum function returns a Null (Null: A value you can enter in a field or use in expressions and queries to indicate missing or unknown data. In Visual Basic, the Null keyword indicates a Null value. Some fields, such as primary key fields, can't contain Null values.).

Remarks
For example, you could use the DSum function in a calculated field expression in a query to calculate the total sales made by a particular employee over a period of time. Or you could use the DSum function in a calculated control to display a running sum of sales for a particular product.

If no record satisfies the criteria argument or if domain contains no records, the DSum function returns a Null.

Whether you use the DSum function in a macro, module, query expression, or calculated control, you must construct the criteria argument carefully to ensure that it will be evaluated correctly.

You can use the DSum function to specify criteria in the Criteria row of a query, in a calculated field in a query expression, or in the Update To row of an update query (update query: An action query (SQL statement) that changes a set of records according to criteria (search conditions) that you specify.).

Note   You can use either the DSum or Sum function in a calculated field expression in a totals query (totals query: A query that displays a summary calculation, such as an average or sum, for values in various fields from a table or tables. A totals query is not a separate kind of query; rather, it extends the flexibility of select queries.). If you use the DSum function, values are calculated before data is grouped. If you use the Sum function, the data is grouped before values in the field expression are evaluated.

You may want to use the DSum function when you need to display the sum of a set of values from a field that is not in the record source for your form or report. For example, suppose you have a form that displays information about a particular product. You could use the DSum function to maintain a running total of sales of that product in a calculated control.

Tip   If you need to maintain a running total in a control on a report, you can use the RunningSum property of that control if the field on which it is based is included in the record source for the report. Use the DSum function to maintain a running sum on a form.

Note   Unsaved changes to records in domain aren't included when you use this function. If you want the DSum function to be based on the changed values, you must first save the changes by clicking Save Record on the File menu, moving the focus to another record, or by using the Update method.

Example
The following example returns the summation of the Freight field for orders shipped to the United Kingdom. The domain is an Orders table. The criteria argument restricts the resulting set of records to those for which ShipCountry equals UK.

Dim curX As Currency
curX = DSum ("[Orders]![Freight] ", "[Orders]", "[ShipCountry] = 'UK'")

DSUM can be from a table or a query

Remember a query can be considered a type of table as it represents a view from a table

So yes

DSUM("queryfield","query","optional filters")



One thing u cant do with these functions is link in other tables/queries. It can only be one table/query lookup

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