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@c This file is part of the Gamma manual.
@c Copyright (C) 2010 Sergey Poznyakoff
@c See gamma.texi for copying conditions.
@c *******************************************************************
The @samp{(gamma sql)} module provides interface with MySQL and
PostfeSQL database management systems.
Usage:
@lisp
(use-modules ((gamma sql)))
@end lisp
@deffn {Scheme procedure} sql-open-connection params
This function opens a connection to the @acronym{SQL}
server and returns a connection object. This object is
then used as argument to @code{sql-query} and
@code{sql-close-connection} functions.
The @code{params} argument supplies the connection parameters.
It is a list of conses, each of which is composed from a keyword
and a value.
@defvr {Keyword} #:iface
Defines the type of the @acronym{SQL} interface. Valid values are:
@samp{"mysql"}, to connect to a MySQL server, and @samp{"pgsql"}, to
connect to a Postgres server.
@end defvr
@defvr {Keyword} #:host
Defines server host name. The value is a string, containing the host
name or @acronym{ASCII} representation of the host IP address.
@end defvr
@defvr {Keyword} #:port
Defines the port number server is listening on. The value is a
decimal port number.
@end defvr
@defvr {Keyword} #:socket
If the @acronym{SQL} server is listening on a socket, this keyword
defines the @acronym{UNIX} pathname of the socket. This keyword
cannot be used together with @samp{#:host} or @samp{#:port} keyword
pairs.
@end defvr
@defvr {Keyword} #:user
Sets the @acronym{SQL} user name.
@end defvr
@defvr {Keyword} #:pass
Sets the @acronym{SQL} user password.
@end defvr
@defvr {Keyword} #:db
Sets the database name.
@end defvr
@defvr {Keyword} #:ssl-cert
Defines full pathname of the @acronym{SSL} certificate to use. If
this keyword is present, the connection with the server will be
encrypted using @acronym{SSL}.
Currently it is implemented only for MySQL connections.
@end defvr
@defvr {Keyword} #:config-file
Use the specified MySQL configuration file to obtain missing parameters.
@end defvr
@defvr {Keyword} #:config-group
Obtain missing parameters from the specified group in the MySQL
configuration file (see @samp{#:config-file}, above).
@end defvr
@end deffn
@deffn {Scheme procedure} sql-close-connection conn
Close the @acronym{SQL} connection. The @var{conn} must be a
connection descriptor returned from a previous call to
@code{sql-open-connection}.
@end deffn
@deffn {Scheme procedure} sql-query conn query
@var{Conn} is a connection descriptor returned from a previous call to
@code{sql-open-connection}, and @var{query} is a valid @acronym{SQL}
query. This function executes the query and returns its results.
If @var{query} is a @code{SELECT} query (or a similar query, returning
tuples), the return is a list, each element of which is a list
representing a row. Elements of each row (@dfn{columns}) are string
values.
If @var{query} results in some modifications to the database (e.g. an
@code{UPDATE} statement), the @code{sql-query} function returns
the number of affected database rows.
@end deffn
@defvr {Error Keyword} gsql-error
An error of this type is raised when any of the above functions
fails. Two arguments are supplied: a string describing the error,
and error message from the underlying @acronym{SQL} implementation.
@end defvr
@deffn {Scheme syntax} sql-catch-failure (handler) expr
@deffnx {Scheme syntax} sql-catch-failure expr
This syntax executes the Scheme expression @var{expr} and calls
@code{handler} if a @code{gsql-error} exception occurs. The handler
must be declared as follows:
@lisp
(define (handler err descr)
...)
@end lisp
In its second form, @code{sql-catch-failure} calls a function named
@code{sql-error-handler} if a @code{gsql-error} exception occurs.
The @code{sql-error-handler} must be declared by the user.
@end deffn
@deffn {Scheme syntax} sql-ignore-failure (value) expr
@deffnx {Scheme syntax} sql-ignore-failure expr
Evaluates Scheme expression @var{expr} and returns the result of
evaluation, or @var{value} if a @code{gsql-error} exception occurs.
In its second form, returns @code{#f} in case of error.
@end deffn
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