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NAME: dbbylist
FUNCTION:
Return the bylist for a compute row.
SYNTAX:
BYTE *dbbylist(dbproc, computeid, size)
DBPROCESS *dbproc;
int computeid;
int *size;
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COMMENTS:
o dbbylist() returns the bylist for a compute row. (A SELECT
statement's COMPUTE clause may contain the keyword BY, followed
by a list of columns. This list, known as the "bylist,"
divides the results into subgroups, based on changing values in
the specified columns. The COMPUTE clause's row aggregate is
applied to each subgroup, generating a compute row for each
subgroup.)
o dbresults() must return SUCCEED before the application calls
this routine.
o Assume the following command has been executed:
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select dept, name, year, sales from employee
order by dept, name, year
compute count(name) by dept,name
The call dbbylist(dbproc, 1, &size) sets size to 2, because
there are two items in the bylist. It returns a pointer to an
array of two BYTES, which contain the values 1 and 2, indicat-
ing that the bylist is composed of columns 1 and 2 from the
select-list.
PARAMETERS:
dbproc - A pointer to the DBPROCESS structure that provides the
connection for a particular front-end/SQL Server process. It
contains all the information that DB-Library uses to manage
communications and data between the front end and SQL Server.
computeid - The id that identifies the particular compute row of
interest. A SQL SELECT statement may have multiple COMPUTE
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clauses, each of which returns a separate compute row. The
computeid corresponding to the first COMPUTE clause in a
SELECT is 1. The computeid is returned by dbnextrow() or
dbgetrow().
size - A pointer to an integer, which dbbylist() sets to the
number of elements in the bylist.
RETURNS:
A pointer to an array of BYTEs containing the numbers of the
columns that compose the bylist for the specified compute. The
array of BYTEs is part of the DBPROCESS, so you must not free it.
If the computeid is out of range, NULL is returned.
Call dbcolname() to derive the name of a column from its number.
The size of the array is returned in the size parameter. A size
of 0 indicates that either there is no bylist for this particular
compute or the computeid is out of range.
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SEE ALSO:
dbadata, dbadlen, dbaltlen, dbalttype, dbcolname, dbgetrow,
dbnextrow