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lua-mysql is a MySQL client library for Lua. It is compatible with Lua 5.2.3(or above) and based on the MySQL C API provided by the official MySQL library.

Lua APIs

First you need to use mysql = require('luamysql') to import a table named mysql(or any other valid name).

  • client, errmsg = mysql.newclient(dbarg)

    • Attempts to establish a connection to a MySQL server specified by dbarg. If successfully executed, a valid MySQL client client, plus a nil for errmsg, are returned; otherwise client will be nil and an error message errmsg is returned. See luamysql-demo.lua for more details about dbarg.
  • errmsg = client:ping()

    • Checks whether the connection to the server is working. If the connection has gone down and auto-reconnect is enabled an attempt to reconnect is made. If the connection is down and auto-reconnect is disabled, an error message errmsg is returned.
  • errmsg = client:selectdb(dbname)

    • Causes the database specified by dbname to become the default (current) database of the client. nil is returned if successfully executed, otherwise an error message errmsg is returned.
  • errmsg = client:setcharset(charset)

    • Sets the default character set to be charset for the current connection. nil is returned if successfully executed, otherwise an error message errmsg is returned.
  • result, errmsg = client:escape(str)

    • Converts the str to a legal SQL string that can be used in a SQL statement. If successfully executed, a result containing a valid string, and a nil for errmsg, are returned; otherwise the result will be nil, and an error message errmsg is returned.
  • result, errmsg = client:execute(sqlstr)

    • Executes a SQL statement sqlstr. If successfully executed, a result containing all information, and a nil for errmsg, are returned; otherwise the result will be nil, and the error message errmsg tells what happened.
  • size = result:size()

    • Returns the number of record(s) in the result. nil is returned if error occurs.
  • fieldnamelist = result:fieldnamelist()

    • Returns the fieldname list for the result. nil is returned if error occurs.
  • result:recordlist()

    • Returns an iteration closure function which can be used in the for ... in form. nil is returned if error occurs. Each record returned by the iterator function is an array containing values corresponding to the fieldname list which is the result of result:fieldnamelist().

See luamysql-demo.lua for more details.

C Library

lua-mysql can also be integrated with C/C++ programs for executing Lua scripts. See host.c for how to import it into C/C++ environment.

FAQ

  • If you try to run luamysql-demo.lua with the following command:

    $ lua luamysql-demo.lua

    but encounter an error message like this:

    lua dynamic libraries not enabled; check your Lua installation

    which means you need to re-compile Lua with extra arguments to enable loading dynamic libraries. For example, in Linux systems:

    $ make posix MYCFLAGS="-DLUA_USE_DLOPEN -fPIC" MYLIBS=-ldl

  • If there is an error message like this:

    multiple Lua VMs detected

    you may re-compile the Lua interpreter with option -Wl,-E.

Enjoy it!

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MySQL client for Lua

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