bionic (3) tdbc_resultset.3tcl.gz
NAME
tdbc::resultset - TDBC result set object
SYNOPSIS
package require tdbc 1.0
package require tdbc::driver version
tdbc::driver::connection create db ?-option value...?
set stmt [db prepare sql-code]
set resultset [$stmt execute ?args...?]
$resultset columns
$resultset rowcount
$resultset nextrow ?-as lists|dicts? ?--? varname
$resultset nextlist varname
$resultset nextdict varname
$resultset nextresults
$resultset allrows ?-as lists|dicts? ?-columnsvariable name? ?--?
$resultset foreach ?-as lists|dicts? ?-columnsvariable name? ?--? varname script
$resultset close
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DESCRIPTION
Every database driver for TDBC (Tcl DataBase Connectivity) implements a result set object that represents
a the results returned from executing SQL statement in a database. Instances of this object are created
by executing the execute object command on a statement object.
The columns object command returns a list of the names of the columns in the result set. The columns will
appear in the same order as they appeared in the SQL statement that performed the database query. If the
SQL statement does not return a set of columns (for instance, if it is an INSERT, UPDATE, or DELETE
statement), the columns command will return an empty list.
The rowcount object command returns the number of rows in the database that were affected by the
execution of an INSERT, UPDATE or DELETE statement. For a SELECT statement, the row count is
unspecified.
The nextlist object command sets the variable given by varname in the caller's scope to the next row of
the results, expressed as a list of column values. NULL values are replaced by empty strings. The columns
of the result row appear in the same order in which they appeared on the SELECT statement. The return of
nextlist is 1 if the operation succeeded, and 0 if the end of the result set was reached.
The nextdict object command sets the variable given by varname in the caller's scope to the next row of
the results, expressed as a dictionary. The dictionary's keys are column names, and the values are the
values of those columns in the row. If a column's value in the row is NULL, its key is omitted from the
dictionary. The keys appear in the dictionary in the same order in which the columns appeared on the
SELECT statement. The return of nextdict is 1 if the operation succeeded, and 0 if the end of the result
set was reached.
The nextrow object command is precisely equivalent to the nextdict or nextlist object command, depending
on whether -as dicts (the default) or -as lists is specified.
Some databases support the idea of a single statement that returns multiple sets of results. The
nextresults object command is executed, typically after the nextlist of nextdict object command has
returned 0, to advance to the next result set. It returns 1 if there is another result set to process,
and 0 if the result set just processed was the last. After calling nextresults and getting the return
value of 1, the caller may once again call columns to get the column descriptions of the next result set,
and then return to calling nextdict or nextlist to process the rows of the next result set. It is an
error to call columns, nextdict, nextlist or nextrow after nextresults has returned 0.
The allrows object command sets the variable designated by the -columnsvariable option (if present) to
the result of the columns object command. It then executes the nextrow object command repeatedly until
the end of the result set is reached. If nextresults returns a nonzero value, it executes the above two
steps (columns followed by iterated nextrow calls) as long as further results are available. The rows
returned by nextrow are assembled into a Tcl list and become the return value of the allrows command; the
last value returned from columns is what the application will see in -columnsvariable.
The foreach object command sets the variable designated by the -columnsvariable option (if present) to
the result of the columns object command. It then executes the nextrow object command repeatedly until
the end of the result set is reached, storing the successive rows in the variable designated by varName.
For each row, it executes the given script. If the script terminates with an error, the error is reported
by the foreach command, and iteration stops. If the script performs a break operation, the iteration
terminates prematurely. If the script performs a continue operation, the iteration recommences with the
next row. If the script performs a return, results are the same as if a script outside the control of
foreach had returned. Any other unusual return code terminates the iteration and is reported from the
foreach.
Once nextrow returns 0, the foreach object command tries to advance to the next result set using
nextresults. If nextresults returns 1, the above steps (columns and nextrow, with script invocation) are
repeated as long as more result sets remain. The script will always see the correct description of the
columns of the current result set in the variable designated byt -columnsvariable. At the end of the
call, the variable designated by -columnsvariable will have the description of the columns of the last
result set.
The close object command deletes the result set and frees any associated system resources.
SEE ALSO
encoding(3tcl), tdbc(3tcl), tdbc::connection(3tcl), tdbc::statement(3tcl), tdbc::tokenize(3tcl)
KEYWORDS
TDBC, SQL, database, connectivity, connection, resultset, statement, bound variable, stored procedure,
call
COPYRIGHT
Copyright (c) 2008 by Kevin B. Kenny.