LuaSQL Access

In this article, we will explore LuaSQL access, and provide examples of how to use them to access and manipulate data in various databases.

One common use case for Lua is in database applications, where Lua scripts can be used to access and manipulate data stored in a variety of databases. This allows developers to write custom scripts and applications to work with databases.

There are several Lua libraries available for working with databases, each with its own strengths and weaknesses. Some libraries provide a lightweight, simple interface for accessing data, while others provide more advanced features and integration with specific database systems.

Some popular Lua libraries include LuaSQL, Redis-lua and Mongorover. In this article we will focus on the LuaSQL library.

LuaSQL

LuaSQL is a Lua library that enables developers to access and interact with various SQL databases, including MySQL, PostgreSQL, SQLite, and more.

The library provides a uniform API that allows for the execution of SQL queries, fetching of results, and management of transactions, among other operations.

This makes it easier for Lua programmers to work with databases, regardless of the specific database technology being used.

LuaSQL Setup

In order to use LuaSQL, you need to install it and the database driver for the database you intend to work with.

The general steps for installing LuaSQL are as follows:

Install Lua

LuaSQL is a Lua library, so you need Lua installed first. For installation, check out our article on Lua installation.

Install the LuaRocks package manager

LuaRocks is a package manager for Lua modules and applications. You can download the latest LuaRocks version from the official website at https://luarocks.org and follow the guidelines for proper installation.

Install the LuaSQL library and the corresponding database driver:

Once LuaRocks is installed, you can use it to install LuaSQL and the corresponding database driver.

For example, if you want to work with MySQL, you can install the LuaSQL MySQL driver by running the following command in your terminal:

luarocks install luasql-mysql

By doing this, you will download and install the LuaSQL library and the MySQL driver.

Connect to the database with the LuaSQL library:

Once you have installed LuaSQL and the corresponding driver, you can load the LuaSQL library as follows:

local luasql = require "luasql.<driver>"

In the above code, replace <driver> with the name of the driver you installed, such as “mysql” or “sqlite3“. When the library has been loaded, you can use its functions to connect to a database, execute queries, and fetch results.

The following example shows how to connect to a MySQL database using LuaSQL:

local luasql = require "luasql.mysql"
local env = luasql.mysql()
local con = env:connect("database_name", "username", "password", "hostname", port)

Enter your database credentials for the “database_name“, “username“, “password“, “hostname“, and “port” fields. When you have connected to the database, you can run SQL queries using the con:execute() method.

There you go! Your Lua scripts can now connect to and work with SQL databases with LuaSQL.

Let’s examine the execution of SQL statements in Lua more closely.

SELECT Statement

A SELECT statement is a SQL statement that retrieves data from a database.

This method retrieves specific information from one or more tables based on criteria specified in the query.

Here is an example that uses the SELECT statement in Lua:

-- Load the LuaSQL MySQL driver
local mysql = require "luasql.mysql"

-- Connect to the MySQL database
local env = mysql.mysql()
local conn = env:connect("mydatabase", "username", "password", "hostname", port)

-- Execute a select statement
local cursor = conn:execute("SELECT * FROM dbtable")

-- Loop through the results and print them
local row = cursor:fetch({}, "a")
while row do
print(row.id, row.name, row.email)
row = cursor:fetch({}, "a")
end

-- Close the cursor and database connection
cursor:close()
conn:close()

• The LuaSQL MySQL driver is used to connect to a MySQL database.
• Using a select statement, it retrieves all records from “dbtable”.
• The results are then looped through and printed to the console.
• Lastly, the cursor and database connection are closed.

UPDATE Statement

An UPDATE statement is a type of SQL statement used to modify existing data in a database table. It allows you to change the values of one or more columns in one or multiple rows of a table, based on a specified condition.

Following example is used to illustrate the UPDATE statement in Lua:

-- Load the MySQL driver
local mysql = require("luasql.mysql")

-- Create a connection to the database
local env = assert(mysql.mysql())
local conn = assert(env:connect("mydatabase", "username", "password", "hostname", port))

-- Define the UPDATE statement
local stmt = assert(conn:prepare("UPDATE dbtable SET name = ? WHERE id = ?"))

-- Execute the statement with the desired values
stmt:execute("Jane", 456)

-- Close the database connection
stmt:close()
conn:close()
env:close()

First we load the LuaSQL MySQL driver and create a connection to a MySQL database using our database credentials.

Next, we prepare an UPDATE statement to update the “name” column of a record in the “mytable” table with a specific “id” value.

We use placeholders like “?” for the values that will be supplied later.

By passing the name and id parameters as arguments to the execute method, we execute the statement. Finally, we close the statement and database connections.

INSERT Statement

An INSERT statement is an SQL statement used to add new data to a database table.

It allows you to specify the values of one or more columns in a table for a new row of data to be added.

Below example is used for the demonstration of an INSERT statement:

-- Load the MySQL driver
local mysql = require("luasql.mysql")

-- Connect to the MySQL database
local env = assert(mysql.mysql())
local conn = assert(env:connect("mydatabase", "myusername", "mypassword", "hostname",port))

-- Define the query to insert data
local query = "INSERT INTO dbtable (name, email) VALUES ('Jane', '[email protected]')"

-- Execute the query
assert(conn:execute(query))

-- Close the database connection
conn:close()
env:close()

First of all the mysql.mysql() function loads the MySQL driver, and env:connect() establishes a connection to the database using the specified credentials. The query variable holds the SQL statement to insert data into the “dbtable” table.

The conn:execute() method executes the query, and the assert function ensures it completes successfully. Finally, the conn:close() and env:close() methods are called to close the database connection.

DELETE Statement

In SQL, a DELETE statement deletes one or more rows from a table.

For your understanding let’s take a quick look at an example:

local mysql = require "luasql.mysql"

-- Create a connection to the MySQL database
local env = assert(mysql.mysql())
local conn = assert(env:connect("mydatabase", "myusername", "mypassword", "hostname",port))

-- Define the DELETE statement
local query = [[
DELETE FROM dbtable
WHERE id = 456
]]

-- Execute the statement
local cursor = assert(conn:execute(query))

-- Close the connection
cursor:close()
conn:close()
env:close()

This code connects to a MySQL database using LuaSQL, then executes a DELETE statement that removes a row from a table where the id column equals 456. Finally, the connection is closed.

CREATE TABLE Statement

The CREATE TABLE statement creates a new table in a database. As well as defining the name of the table and its columns, it also specifies their data types and constraints.

Following example focuses on the implementation of CREATE TABLE statement in Lua:

-- Load the MySQL driver
local mysql = require("luasql.mysql")

-- Create a connection object
local env = assert(mysql.mysql())
local conn = assert(env:connect("my_database", "my_username", "my_password", "hostname",port))

-- Execute an SQL query to create a new table
local query = [[
CREATE TABLE users (
id INT PRIMARY KEY AUTO_INCREMENT,
name VARCHAR(50),
)
]]
assert(conn:execute(query))

-- Close the connection
conn:close()
env:close()

After loading the MySQL driver via require(“luasql.mysql“) and establishing a connection with the database, we execute an SQL query using the execute() method of the connection object to create a new table named “users” with two columns: “id” (an auto-incrementing primary key) and “name” (a VARCHAR column that can hold up to 50 characters).

Finally, we close the connection and environment objects using the close() method.

To ensure you’re up to date with the latest developments, be sure to subscribe to our newsletter.