A small MySQL client library for chicken-scheme. This egg makes it possible to execute an SQL query on a MySQL database.
Requires MySQL database system development components, libmysqlclient and mysql_config.
The mysql_config program needs to be in the $PATH so the linker can find the native MySQL libraries.
On a Linux machine, consider trying:
apt-get install libmysqlclient-dev
chicken-install -s mysql-client
With MySQL 5.5.24, the compiled mysql-client library does not have an absolute path to the libmysqlclient dependency, this can be corrected with the following command
sudo install_name_tool -change libmysqlclient.18.dylib $(mysql_config --variable=pkglibdir)/libmysqlclient.18.dylib /usr/local/lib/chicken/6/mysql-client.so
- make-mysql-connection hostname username password schemaprocedure
This procedure will return a procedure that contains a closed off MySQL connection and can execute a query when called:
- unnamed-mysql-connection-closure sql-statement #!rest placeholder-values-alistprocedure
This will return a row fetcher closure, either provide a procedure to apply to all rows or call with no parameters to return the next row:
- unnamed-mysql-row-fetcher-closure #!rest thunkprocedure
Alternatively to apply a procedure directly to the MySQL connection pointer, pass a procedure:
- mysql-null valueparameter
MySQL null field parameter. Called with one argument, will set the value representing a MySQL null.
- mysql-null? valueprocedure
Returns true if value is the MySQL null representative.
Here is a trivial example:
(use mysql-client) (define mysql (make-mysql-connection "localhost" "root" #f "information_schema")) (define fetch (mysql "SELECT * FROM schemata")) (display (fetch)) (newline)
Here is an example that will use the mysql_real_escape_string MySQL function to safely escape parameters in the query string using a placeholder syntax. In this case, the first argument is a string containing an SQL query, and the second argument will be an association list where the key represents the placeholder symbol in the query.
(use mysql-client) (define mysql (make-mysql-connection "localhost" "username" "secret" "database")) (define fetch (mysql "SELECT * FROM t1 WHERE c1 = '$1' OR c2 = '$2'" '(($1 . "value 1';' ;")($2 . "value 2'; drop database; ")))) (display (fetch)) (newline)
Other placeholder conventions are possible as well, as the keys from the association list are matched in the query.
(define fetch (mysql "SELECT * FROM t WHERE created_on < '?to' AND created_on > '?from' LIMIT 5" '((?from . "2012-04-01 00:00")(?to . "2012-04-01 24:00"))))
To apply a procedure to every row, pass a procedure to the fetcher closure.
(fetch (lambda(r) (printf "~S~%" r)))
For power users, to access directly the MySQL connection object pointer, pass a procedure to the MySQL client closure.
(use mysql-client) (define mysql (make-mysql-connection "localhost" "username" "secret" "database")) (define fetch (mysql (lambda(c)(printf "~S ~%" c)))) (display (fetch)) (newline)
Copyright (C) 2012, A. Carl Douglas All rights reserved.
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- 0.8 Added mysql-null? predicate and mysql-null parameter to specify how null fields are represented.
- 0.7 Use myql_config --cflags instead of --include when compiling, detect MySQL 5.5.24 and attempt to apply install_name_tool work around.
- 0.6 Fixed setup so it passes all options returned from mysql_config through to the compiler.
- 0.5 Return fetch procedure that returns false when there are no rows. Fetch procedure can apply a procedure to all rows.
- 0.4 Initial publication.