MySQL

Melang only support MySQL 8.0, because that version supports asynchronous functions.

If you want to activate MySQL APIs, you should install MySQL library and header files before Melang installation.

Import

mysql = Import('mysql');

Here is the Set Mysql:

Mysql {
  fd;
  connect(host, port, dbname, username, password);
  close();
  autocommit(mode);
  commit();
  rollback();
  error();
  errno();
  execute(sql);
};

fd

fd is a memory block of MySQL structure in C. So it’s value is a memory address, and it’s read-only property.

connect

Create a session on MySQL server.

connect(host, port, dbname, username, password);

Input:

• host - a host string of MySQL server.
• port - an integer port number that MySQL server listening.
• dbname - string database name.
• username - string username.
• password - string password.

Return value:

• true on success, otherwise false.

Error:

• any error will be thrown if encountered.

close

Close session.

close();

Input: None.

Return value:

• always nil.

Error:

• any error will be thrown if encountered.

autocommit

Switch autocommit mode.

autocommit(mode);

Input:

• mode - a boolean value. Set true If want to auto commit, otherwise false.

Return value:

• true on success, otherwise false.

Error:

• any error will be thrown if encountered.

commit

Commit the current transaction.

commit();

Input: None.

Return value:

• true on success, otherwise false.

Error:

• any error will be thrown if encountered.

rollback

Roll back the current transaction.

rollback();

Input: None.

Return value:

• true on success, otherwise false.

Error:

• any error will be thrown if encountered.

error

Get error message.

error();

Input: None.

Return value:

• a string error message returned on success, otherwise false returned.

Error:

• any error will be thrown if encountered.

errno

Get error number.

errno();

Input: None.

Return value:

• an integer error number returned on success, otherwise false returned.

Error:

• any error will be thrown if encountered.

execute

Execute SQL.

execute(sql);

Input:

• sql - a string SQL.

Return value:

• Reading operation returns an array whose every element is also an array that is equivalent to a record in query results.
• Writing operation returns a boolean value. true on success, otherwise false.

Error:

• any error will be thrown if encountered.

Example

There is a database named test, and there is a table people in it:

CREATE TABLE `people` (
  `id` int unsigned NOT NULL AUTO_INCREMENT,
  `age` tinyint unsigned NOT NULL DEFAULT '0',
  `name` varchar(32) NOT NULL DEFAULT '',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Our program:

mysql = Import('mysql');
sys = Import('sys');

m = $mysql; // or m = $Mysql; both are the same. the value of mysql is 'Mysql'.
m.connect('127.0.0.1', 3306, 'test', 'root', '.../*password*/');
sys.print(m.execute('insert into `people` (name, age) values("Tom", 18)'));
result = m.execute('select `name`, `age` from `people`');
sys.print(result);
m.close();

The output is:

true
[[Tom, 18, ], ]