Database Functions

$Header: /cvsroot/aolserver/aolserver.com/docs/devel/tcl/api/db.html,v 1.2 2004/07/20 23:44:26 dossy Exp $


Note! Updated Tcl API documentation in progress is now available on the wiki.


ns_db

Access a database.

Syntax

ns_db bindrow dbhandle
ns_db bouncepool dbhandle
ns_db cancel dbhandle
ns_db close dbhandle
ns_db connected dbhandle
ns_db datasource dbhandle
ns_db dbtype dbhandle
ns_db dml dbhandle sql
ns_db driver dbhandle
ns_db exception dbhandle
ns_db exec dbhandle sqlcommand
ns_db flush dbhandle
ns_db gethandle ?-timeout timeout? [poolname] nhandles
ns_db getrow dbhandle setId
ns_db open driver datasource user password
ns_db poolname dbhandle
ns_db pools
ns_db releasehandle dbhandle
ns_db 1row dbhandle sql
ns_db 0or1row dbhandle sql
ns_db password dbhandle
ns_db select dbhandle sql
ns_db setexception dbhandle code message
ns_db sp_exec dbhandle
ns_db sp_getparams
ns_db sp_returncode dbhandle
ns_db sp_setparam dbhandle varname vartype inout value
ns_db sp_start dbhandle procname
ns_db user dbhandle
ns_db verbose dbhandle ?on | off?

Description

ns_db bindrow returns an ns_set structure whose key names are the column names of the rows returned by the SQL command previously-executed with ns_db exec. If the database is not currently returning rows (i.e., a status other than NS_ROWS was returned by ns_db exec), an error is thrown. The dbhandle argument is a database handle (obtained with ns_db gethandle).

ns_db bouncepool marks all database handles for the specified database pool as stale. When any database handle currently open is put back into the pool, its connection to the database will be reset.

ns_db cancel cancels the current operation.

ns_db close closes the connection. Use this function only on handles that were obtained by the ns_db open function. However, the server automatically close handles when the operation is complete, so you don't normally have to call this function.

ns_db connected returns a boolean value indicating whether the connection to the database pool is made.

ns_db datasource returns the data source for the database pool (e.g., default:mydb).

ns_db dbtype returns the database type of the database pool.

ns_db dml executes SQL that should be data manipulation language such as an insert or update, or data definition language such as a create table.

ns_db driver returns the name of the driver of the handle (e.g., "SOLID").

ns_db exception returns the most recent exception for the database pool.

ns_db exec executes the specified SQL command. It returns either NS_DML (if the SQL command is a DML or DDL command) or NS_ROWS (if the SQL command returns rows, such as a SELECT). If an error occurs executing the SQL command, an error is thrown. The dbhandle argument is a database handle (obtained with ns_db gethandle). This function can be used for true ad hoc querying, where you don't know what kind of SQL command will be executed.

ns_db flush flushes the results of an SQL select so you do not need to use ns_db getrow to get all the rows and throw them away.

ns_db gethandle returns the specified number of handles from the specified pool. If poolname is not specified, the Defaultpool from the configuration file is used. If nhandles is not specified, 1 handle is returned. (Note that if you specify nhandles, you must also specify a poolname.) If not enough handles are available to fulfill the request, it waits until they are available. You must request all the handles you will need for a specific pool with one call to ns_db gethandle. You must release all your database handles explicitly (with ns_db releasehandle) before acquiring more. If you request multiple handles from the database, this function returns a Tcl list of database handles (space delimited). In this case, each handle must be released with a separate call to ns_db releasehandle.

If a timeout is not specified or timeout is zero, ns_db gethandle will wait indefinitely (perhaps forever) for the requested number of handles to become available. If timeout is greater than zero, ns_db gethandle will either return with the handles within that time period, or return "" if the time period was exceeded, or generate a Tcl error of the form "could not allocate n handle(s) from pool 'poolname'. If timeout is less than zero, ns_db gethandle will not block. It will either return with the handles, or generate the above Tcl error. See the examples for ns_db gethandle, below.

ns_db getrow fetches the next row waiting to be retrieved after an ns_db select. The data is dumped right into the set associated with SETID, which should be the set returned by the ns_db select. It returns "1" if there are more rows waiting and returns "0" otherwise. If you call ns_db getrow again after already receiving "0" on the previous call, an error is returned.

ns_db open returns a handle at a lower level, circumventing the pools.

ns_db poolname returns the database pool that this handle came from.

ns_db pools returns a list of all database pools.

ns_db releasehandle puts the handle back in the pool. When your operation has finished running, the server will automatically return any handles to their pools, so you don't normally have to call this function.

ns_db 1row expects the SQL to be a select statement that returns exactly one row and returns that row as an ns_set.

ns_db 0or1row expects the SQL to be a select statement that returns exactly zero or one row. On zero rows, a null string is returned. On one row, a newly allocated ns_set is returned.

ns_db password returns the password of the user for the database pool.

ns_db select executes the SQL statement on the database server. It returns an ns_set with the keys set to the column names that were selected. Use ns_db getrow to retrieve rows. You cannot perform nested select statements. Before you start a new select statement, you must first either retrieve all the rows from the first select or use the ns_db flush statement to flush any rows not yet retrieved.

ns_db setexception returns the specified status code and message to the client.

ns_db sp_exec executes a stored procedure that has been initialized with ns_db sp_start and ns_db sp_setparam. It returns "NS_DML" if the command was succsesfully executed but did not return rows, or it returns "NS_ROWS" if the command was successfully executed and did return rows (which can then be fetched with ns_db bindrow and ns_db getrow). It throws an error if the command failed. This function is implemented only for the Sybase database driver. See the Examples section, below, for an example of this function.

ns_db sp_getparams gets any output parameters set after executing a stored procedure with ns_db sp_exec. It returns an ns_set or throws an error on failure. This function is implemented only for the Sybase database driver. See the Examples section, below, for an example of this function.

ns_db sp_returncode gets the return code from a stored procedure. It must be called after ns_db sp_exec. This function is implemented only for the Sybase database driver. See the Examples section, below, for an example of this function.

ns_db sp_setparam sets a parameter for a call to a stored procedure. The varname is the name of the variable, for example "@name". The vartype is the data type of this parameter, for example "varchar". The inout argument indicates whether it's an input or output parameter. It must be set to either "in" or "out". The value is the paramter value to send. This function returns 1 on success and throws an error on failure. This function is implemented only for the Sybase database driver. See the Examples section, below, for an example of this function.

ns_db sp_start begins execution of the stored procedure called procname. It returns 0 on success and throws an error on failure. This function is implemented only for the Sybase database driver. See the Examples section, below, for an example of this function.

ns_db user returns the user (as specified for the User parameter of the configuration file) for the database pool.

ns_db verbose changes the verbose setting (the Verbose parameter in the configuration file) for the database pool.

Examples

1. Here's an example ADP that runs a stored procedure called "p_TestProc" in a pool called "sybase":

#
# The new stored procedure commands that I've implemented are:
#
#   ns_db sp_start      $dbhandle $procname
#   ns_db sp_setparam   $dbhandle $varname, $vartype, in|out, $value
#   ns_db sp_exec       $dbhandle
#   ns_db sp_returncode $dbhandle
#   ns_db sp_getparams  $dbhandle
#
# Look for them and their usage below...
#

set formdata [ns_conn form $conn]
#set pool  [ns_set get $formdata "pool"]
#set pool  "sybdoug"
set pool "sybase"

if {$pool == ""} {
    ns_puts "

No database pool specified.

" ns_adp_break } set db [ns_db gethandle $pool] set datasource [ns_db datasource $db] set dbtype [ns_db dbtype $db] set driver [ns_db driver $db] set poolname [ns_db poolname $db] set user [ns_db user $db] set password [ns_db password $db] # # Show some information about this connection to the database. # ns_puts "datasource: $datasource" ns_puts "dbtype: $dbtype" ns_puts "driver: $driver" ns_puts "poolname: $poolname" ns_puts "user: $user" ns_puts "password: $password" # # Turn on server tracing for this handle -- only do this if you need # debug output on the server side. # ns_ext traceon $db "/tmp/sybtrace" # # Create a stored procedure. # set ret [ns_db sp_start $db "p_TestProc"] # # Set the parameters for this stored procedure. The SQL definition of # this procedure is: # # CREATE PROCEDURE p_TestProc(@x int, @y varchar(16) out, @z int out) # # The arguments to ns_db sp_setparam are like this: # # ns_db setparam $dbhandle $varname, $vartype, in|out, $value # set ret [ns_db sp_setparam $db "@x" int in 4] set ret [ns_db sp_setparam $db "@y" varchar out "varchar val"] set ret [ns_db sp_setparam $db "@z" int out 231] # # Execute the stored procedure now # set ret [ns_db sp_exec $db] # # Bind an ns_set to the rows returned from this procedure # set row [ns_db bindrow $db] if {$row == ""} { ns_puts "No row data returned from bindrow." ns_adp_break } # # Display all of the rows returned in a generic way # set numcols [ns_set size $row] for {set i 0} {$i < $numcols} {incr i} { ns_puts "[ns_set key $row $i]" } while {[ns_db getrow $db $row]} { for {set i 0} {$i < $numcols} {incr i} { ns_puts "[ns_set value $row $i]" } } # # Show the return code # ns_puts "Return code: [ns_db sp_returncode $db]" # Process output parameters. The output parameters are returned in an # ns_set with the keys set to the parameter names from the above # setparam calls. All of the parameters that were specified as an # "out" parameter will be represented here if they were defined as # output values in the stored procedure itself. catch { ns_puts "Output parameters: " set paramset [ns_db sp_getparams $db] if {$paramset == "" || $paramset == 0} { ns_puts "sp_getparams failed" } } paramerr if {$paramerr != ""} { ns_puts "getparams generated a database exception" ns_adp_break; } # # Display the output parameters # set numparams [ns_set size $paramset] for {set i 0} {$i < $numcols} {incr i} { set key [ns_set key $paramset $i] ns_puts "Param $key: [ns_set get $paramset $key]" } %>
2. These are valid uses of ns_db gethandle:
ns_db gethandle
# 1 handle from default pool
ns_db gethandle -timeout 23
# 1 handle from default pool, 23 sec timeout
ns_db gethandle -timeout -1 poolname
# 1 handle from poolname, error if not available
ns_db gethandle poolname
# 1 handle from poolname
ns_db gethandle -timeout 23 poolname
# 1 handle from poolname, 23 sec timeout
ns_db gethandle poolname 5
# 5 handles from poolname
ns_db gethandle -timeout 23 poolname 5
# 5 handles from poolname, 23 sec timeout
This is not valid, because nhandles is specified without a poolname:
ns_db gethandle 5
# it thinks 5 is the pool name



ns_dbconfigpath

Get nsdb section name

Syntax

ns_dbconfigpath

Description

This function returns the section name in the configuration file for the nsdb module.



ns_dberror

Return SQL error information

Syntax

ns_dberrorcode dbhandle
ns_dberrormsg dbhandle
ns_dbreturnerror conn dbhandle ?title? ?aftermsg?

Description

ns_dberrorcode returns the 5-character SQL error code for the last database error.

ns_dberrormsg returns a text description of the last database error.

ns_dbreturnerror returns an HTML version of the last database error message to the client. The text in aftermsg is appended to the HTML after the error message.



ns_dbformvalue

Retrieve the value of a column specified by form data

Syntax

ns_dbformvalue formdata colname type valueVar

Description

ns_dbformvalue returns the value of a specified column (colname) in valueVar, given column values encoded as formdata (see page 32). The formdata is an ns_set structure that can be obtained by calling ns_conn form. Specify the datatype of the column in the type argument. Valid type values are text, integer, real, boolean, date, time, or timestamp.

If necessary, ns_dbformvalue combines multiple form elements to get the value, such as for dates.

Use this function for accessing data filled into an automatically-generated search, update, or entry form.



ns_dbformvalueput

Set default values in an HTML form for accessing the database

Syntax

ns_dbformvalueput htmlform colname type value

Description

ns_dbformvalueput sets the default value for the specified column (colname) in an HTML form (htmlform) equal to value. The HTML form does not need to be completely formed; it may be a partial form. Specify the type of the column as text, integer, real, boolean, date, time, or timestamp.



ns_dbquotename

Surround a name by double quotes if it contains a space

Syntax

ns_dbquotename name

Description

ns_dbquotename surrounds name by double quotes if it contains a space. The resulting name can then be used in SQL statements for names of database objects such as tables or columns.



ns_dbquotevalue

Prepare a value string for inclusion in an SQL statement

Syntax

ns_dbquotevalue value {type text}

Description

ns_dbquotevalue prepares a value string for inclusion in an SQL statement. The value is of type text by default. Values of a numeric type in the value string are left alone. A value string of "" is translated into NULL. All other values are surrounded by single quotes, and any single quotes included in the value are escaped (translated into two single quotes).

Example

set value "Charlie's Cheese Factory"
ns_db dml $db \
"insert into companies(name) values ([ns_dbquotevalue $value])"



ns_deleterow

Delete row in specified table corresponding to form data

Syntax

ns_deleterow dbhandle table formdata

Description

ns_deleterow deletes the row encoded as formdata (see page 32) in the specified database and table. The values specifying the exact row to be deleted are encoded in the form data as RowID.columnname. The dbhandle argument is a database handle (obtained with ns_db gethandle).



ns_ext

Perform external database driver operations.

Syntax

ns_ext cpfrom dbhandle file1 file2
ns_ext cpto dbhandle file1 file2
ns_ext dbtype dbhandle
ns_ext gettypes dbhandle
ns_ext identify dbhandle
ns_ext isremote dbhandle
ns_ext mktemp dbhandle
ns_ext number dbhandle
ns_ext ping dbhandle
ns_ext resultid dbhandle
ns_ext resultrows dbhandle
ns_ext rm dbhandle file
ns_ext setmaxrows dbhandle limit
ns_ext traceoff dbhandle
ns_ext traceon dbhandle file

Description

The ns_ext functions are described below. They are only available if an external database driver is loaded. The dbhandle argument for all of the functions is a database handle (obtained with ns_db gethandle poolname).

ns_ext cpfrom copies a local file (file1) from the remote proxy daemon file space (file2). This function (along with mktemp, rm, and cpto) is provided to support environments where the proxy daemon does not share a common file system with the server, allowing SQL statements to reference local temporary files, which can then be copied to the server's local file space.

ns_ext cpto copies a local file (file1) to the remote proxy daemon file space (file2). This function (along with mktemp, rm, and cpfrom) is provided to support environments where the proxy daemon does not share a common file system with the server, allowing SQL statements to reference local temporary files, which can then be copied to the server's local file space.

ns_ext dbtype returns the database type, such as "Sybase".

ns_ext gettypes returns a Tcl list containing the data types for the database.

ns_ext identify returns the proxy daemon identity and version string.

ns_ext isremote returns a boolean value indicating whether or not the database is remote.

ns_ext mktemp creates a unique temporary file in the proxy daemon's file space. This function (along with rm, cpto, and cpfrom) is provided to support environments where the proxy daemon does not share a common file system with the server, allowing SQL statements to reference local temporary files, which can then be copied to the server's local file space.

ns_ext number returns the connection number.

ns_ext ping verifies that the proxy daemon process is running.

ns_ext resultid returns the id of the last object affected by an exec command.

ns_ext resultrows returns the number of rows affected by the last exec command.

ns_ext rm removes a file (file) in the proxy daemon's file space. This function (along with mktemp, cpto, and cpfrom) is provided to support environments where the proxy daemon does not share a common file system with the server, allowing SQL statements to reference local temporary files, which can then be copied to the server's local file space.

ns_ext setmaxrows specifies the limit on the number of rows to be returned.

ns_ext traceoff disables message tracing in the proxy daemon.

ns_ext traceon enables message tracing in the proxy daemon. Trace output is written to the specified file path (file).



ns_insertrow

Insert form data into specified table as a new row.

Syntax

ns_insertrow dbhandle table formdata

Description

ns_insertrow inserts the row encoded as formdata (see page 32) in the specified database and table. The dbhandle argument is a database handle (obtained with ns_db gethandle).



ns_pooldescription

Get database pool description

Syntax

ns_pooldescription poolname

Description

The function returns the descriptive comments assigned to the name of the specified pool in the [ns/db/pools] section in the configuration file.