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NAME: dbadata
FUNCTION:
Return a pointer to the data for a compute column.
SYNTAX:
BYTE *dbadata(dbproc, computeid, column)
DBPROCESS *dbproc;
int computeid;
int column;
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COMMENTS:
o After each call to dbnextrow(), you can use this routine to
return a pointer to the data for a particular column in a com-
pute row. The data is not null-terminated. You can use
dbadlen() to get the length of the data.
o When a column of integer data is summed or averaged, SQL Server
always returns a 4-byte integer, regardless of the size of the
column. Therefore, be sure that the variable which is to con-
tain the result from such a compute is declared as DBINT.
o Here's a short program fragment which illustrates the use of
dbadata():
DBPROCESS *dbproc;
int rowinfo;
DBINT sum;
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/* first, put the commands into the command buffer */
dbcmd(dbproc, "select db_name(dbid), dbid, size from sysusages");
dbcmd(dbproc, " order by dbid");
dbcmd(dbproc, " compute sum(size) by dbid");
/* send the commands to SQL Server and start execution */
dbsqlexec(dbproc);
/* process the command */
dbresults(dbproc);
/* examine the results of the COMPUTE clause */
while((rowinfo = dbnextrow(dbproc)) != NO_MORE_ROWS)
{
if (rowinfo == REG_ROW)
printf("regular row returned.\n");
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else
{
/* This row is the result of a COMPUTE clause, and
* "rowinfo" is the computeid of this COMPUTE clause.
*/
sum = *(DBINT *)(dbadata(dbproc, rowinfo, 1));
printf("sum = %ld\n", sum);
}
}
o The function dbaltbind() automatically binds compute data to
your program variables. It does a copy of the data, but is
often easier to use than dbadata(). Furthermore, it includes a
convenient type conversion capability. By means of this capa-
bility, the application can, among other things, easily add a
null terminator to a result string or convert money and
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datetime data to printable strings.
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
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().
column - The number of the column of interest. The first column
returned is number 1. Note that the order in which compute
columns are returned is determined by the order of the
corresponding columns in the select-list, not by the order in
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which the compute columns were originally specified. For
example, in the following query the result of "sum(price)" is
referenced by giving column a value of 1, not 2:
select price, advance from titles
compute sum(advance), sum(price)
The relative order of compute columns in the select-list,
rather than their absolute position, determines the value of
column. For instance, given the following variation of the
previous SELECT:
select title_id, price, advance from titles
compute sum(advance), sum(price)
the column for "sum(price)" still has a value of 1 and not 2,
because the "title_id" column in the select-list is not a
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compute column and therefore is ignored when determining the
compute column's number.
RETURNS:
A BYTE pointer to the data for a particular column in a particu-
lar compute. Be sure to cast this pointer into the proper type.
A BYTE pointer to NULL is returned if there is no such column or
compute or if the data has a null value.
DB-Library allocates and frees the data space that the BYTE
pointer points to. Do not overwrite this space.
SEE ALSO:
dbadlen, dbaltbind, dbaltlen, dbalttype, dbgetrow, dbnextrow,
dbnumalts