Combines records with identical values in the specified field list into a single record. A summary value is created for each record if you include an SQL aggregate function , such as Sum or Count, in the SELECT statement.
[GROUP BY groupfieldlist]
A SELECT statement containing a GROUP BY clause has these parts:
||The name of the field or fields to be retrieved along with any field-name aliases, SQL aggregate functions, selection predicates (ALL, DISTINCT, DISTINCTROW, or TOP), or other SELECT statement options.
||The name of the table from which records are retrieved.
||Selection criteria. If the statement includes a WHERE clause, the Microsoft Jet database engine groups values after applying the WHERE conditions to the records.
||The names of up to 10 fields used to group records. The order of the field names in groupfieldlist determines the grouping levels from the highest to the lowest level of grouping.
GROUP BY is optional.
Summary values are omitted if there is no SQL aggregate function in the SELECT statement.
Null values in GROUP BY fields are grouped and are not omitted. However, Null values are not evaluated in any SQL aggregate function.
Use the WHERE clause to exclude rows you do not want grouped, and use the HAVING clause to filter records after they have been grouped.
Unless it contains Memo or OLE Object data, a field in the GROUP BY field list can refer to any field in any table listed in the FROM clause, even if the field is not included in the SELECT statement, provided the SELECT statement includes at least one SQL aggregate function. The Microsoft® Jet database engine cannot group on Memo or OLE Object fields.
All fields in the SELECT field list must either be included in the GROUP BY clause or be included as arguments to an SQL aggregate function.