Lua 4Days ORM 10 minutes tutorial

Database configuration

Before the beginning you should add some simple settings to your database configuration. You must create some global variable DB:

DB = {}

Development configurations:

1. new - if this value is true, then previous database was removed and new was created (true by default).
2. backtrace - if this value is true, than you will be able to see in console all Warnings, Errors and Information messages (true by default).
3. DEBUG - if this value is true, you will be able to see in console all SQL queries (true by default).

Database configurations

1. type - by default "sqlite3". Also it can be:
   • "mysql" - for MySQL database
   • "postgres" - for PostgreSQL database (implemented soon)
2. name - this is a path to database file for "sqlite3". For other databases this value contains database name. (by default "database.db")
3. username - database user name (by default nil)
4. password - database password (by default nil)
5. host - database host (by default nil)
6. port - database host port (by default nil)

---

After setting configurations you can add 2 modules import to your file

local Table = require("orm.model")
local fields = require("orm.tools.fields")

Create table

local User = Table({
    __tablename__ = "user",
    username = fields.CharField({max_length = 100, unique = true}),
    password = fields.CharField({max_length = 50, unique = true}),
    age = fields.IntegerField({max_length = 2, null = true}),
    job = fields.CharField({max_length = 50, null = true}),
    time_create = fields.DateTimeField({null = true})
})

For every table is created a column id with PRIMARY KEY field by default.

__tablename__ is required value which should contain the name of the table.

Also you can add different settings to your table fields

1. max_length - it is a maximum allowable value of symbols that you can use in a string
2. unique - if this value is true then all the column's values are unique
3. null - can be true or false. If value is true then value in table will be saved as NULL.
4. default - if you didn't add any value to this field - it is going to be saved as default value.
5. primary_key - If you want to add some value as primary key, you can set this value as true.

Types of table fields

Supported types of table fields

1. CharField - Creates VARCHAR field
2. IntegerField - Creates INTEGER field
3. TextField - Creates TEXT field
4. BooleanField - Creates BOOLEAN field
5. DateTimeField - Creates INTEGER field but brings back os.date instance
6. PrimaryField - Creates INTEGER field with PRIMARY KEY
7. ForeignKey - Creates relationships between tables.

Also you can create your types of table fields. But about it later.

Create data

Try to create a new user:

local user = User({
    username = "Bob Smith",
    password = "SuperSecretPassword",
    time_create = os.time()
})

Now you created new user, but it was not added to database. You can add him.

user:save()

Now this user with all the information is in database. We can get his id

print("User " .. user.username .. " has id " .. user.id)
-- User Bob Smith has id 1

Update data

You can change your data:

user.username = "John Smith"

This value was changed in model, but it has not been changed in database table.

user:save()

Now try to get new username for user:

print("New user name is " .. user.username) -- New user name is John Smith 

You have updated in database only the column that you changed. You can also edit columns for the value by another terms:

User.get:where({time_create__null = true})
        :update({time_create = os.time()})

The conditions will be described in the next chapter

Remove data

And also you can remove your data from table.

user:delete()

You can also delete columns for the value by another terms:

-- add test user
user = User({username = "SomebodyNew", password = "NotSecret"})
user:save()

User.get:where({username = "SomebodyNew"}):delete()

The conditions will be described in the next chapter

Get data

Also we can get data from table. But before this let's create 5 test users.

user = User({username = "First user", password = "secret1", age = 22})
user:save()

user = User({username = "Second user", password = "secret_test", job = "Lua developer"})
user:save()

user = User({username = "Another user", password = "old_test", age = 44})
user:save()

user = User({username = "New user", password = "some_passwd", age = 23, job = "Manager"})
user:save()

user = User({username = "Old user", password = "secret_passwd", age = 44})
user:save()

And now try get one of them:

local first_user = User.get:first()
print("First user name is: " .. first_user.username)
-- First user name is: First user

But also we can get all users from table:

local users = User.get:all()
print("We get " .. users:count() .. " users")
-- We get 5 users

Method count returns number of users in the list.

Limit and Offset

Sometime we need to get not one but not all users. For the first, try to get first 2 users from the table.

users = User.get:limit(2):all()
print("We get " .. users:count() .. " users")
-- We get 2 users
print("Second user name is: " .. users[2].username)
-- Second user name is: Second user

Great! But if we want to get next two users? We can do this by using following example:

users = User.get:limit(2):offset(2):all()
print("Second user name is: " .. users[2].username)
-- Second user name is: New user

Order result

Also you can sort your result by order. We want to sort users from the oldest to the youngest.

users = User.get:order_by({desc('age')}):all()
print("First user id: " .. users[1].id)
-- First user id: 3

But we have 2 users with age 44. We can order them by name.

users = User.get:order_by({desc('age'), asc('username')}):all()

You can order your table query by other parameters too.

Group result

And now try to group your results:

users = User.get:group_by({'age'}):all()
print('Find ' .. users:count() ..' users')
-- Find 4 users

Where and Having

These two methods have the same syntax. But having you can use only with group_by method. There's one simple example:

user = User.get:where({username = "First user"}):first()
print("User id is: " .. user.id) -- User id is: 1

And the same for having:

users = User.get:group_by({'id'}):having({age = 44}):all()
print("We get " .. users:count() .. " users with age 44")
-- We get 2 users with age 44

Great! But what if we need to do more operations than just a differentiation of table fields. We can do that! This is the list with some rules:

For example we use for default colname. It can be any column in your model

1. colname = value - the same as colname = value
2. colname__lt = value - the same as colname < value (value must be a number)
3. colname__lte = value - the same as colname <= value (value must be a number)
4. colname__gt = value - the same as colname > value (value must be a number)
5. colname__gte = value - the same as colname >= value (value must be a number)
6. colname__in = {v1, v2,...,vn} - the same as colname in (value1, value2,...,vn) (vn can be number, string)
7. colname__notin = {v1, v2,...,vn} - the same as colname not in (value1, value2,...,vn) (vn can be number, string)
8. colname__null = value - if value is true then result is colname is NULL, but if value is false then result is colname is not NULL

Super SELECT

But if we do ...

user = User.get:where({age__lt = 30,
                       age__lte = 30,
                       age__gt = 10,
                       age__gte = 10
                })
                :order_by({asc('id')})
                :group_by({'age', 'password'})
                :having({id__in = {1, 3, 5},
                         id__notin = {2, 4, 6},
                         username__null = false
                    })
                :limit(2)
                :offset(1)
                :all()

This example doesn't make sense. But it works!

JOIN TABLES

Now we can create a join of tables. But before that we create some table with foreign key column:

local News = Table({
    __tablename__ = "group",
    title = fields.CharField({max_length = 100, unique = false, null = false}),
    text = fields.TextField({null = true}),
    create_user_id = fields.ForeignKey({to = User})
})

And add two test news:

local user = User.get:first()

local news = News({title = "Some news", create_user_id = user.id})
news:save()

news = News({title = "Other title", create_user_id = user.id})
news:save()

Now try to get all the news from the owner.

local news = News.get:join(User):all()
print("First news user id is: " .. news[1].user.id) -- First news user id is: 1

But if we want to get all users and also to get three news for each user . We can do this by following example:

local user = User.get:join(News):first()
print("User " .. user.id .. " has " .. user.news_all:count() .. " news")
-- User 1 has 2 news
    
for _, user_news in pairs(user.news_all) do
    print(user_news.title)
end
-- Some news
-- Other title

If you want to get all the values from tables you can combine table's names and prefix "_all". Like in previous example

user.news_all

news_all - returns a list of all news for current user or nil if news does not exist.

Create column types

We can create a field type for every table. Try to create EmailField type:

fields.EmailField = fields:register({
    __type__ = "varchar",
    settings = {
        max_length = 100
    },
    validator = function (value)
        return value:match("[A-Za-z0-9%.%%%+%-]+@[A-Za-z0-9%.%%%+%-]+%.%w%w%w?%w?")
    end,
    to_type = function (value)
        return value
    end,
    as = function (value)
        return "'" .. value .. "'"
    end
})

Let's make it step by step:

__type__ - this variable creates the appropriate type in the database ("varchar", "integer", "boolean", "date", "datetime", "text", ...). By default this value is "varchar".

settings -set a field value as default (fields settings was describe later). By default this value is empty.

validator - validates the value of the variable. If value is correct - returns true. If value is not correct it returns false and doesn't update or add rows. By default it always returns true.

to_type - parses value for correct sql save. By default it is not parsed value

as - returns the value from lua to SQL. By default it is not parsed value.

local UserEmails = Table({
    __tablename__ = "user_emails",
    email = fields.EmailField(),
    user_id = fields.ForeignKey()
})

local user_email = UserEmails({
    email = "mailexample.com",
    user_id = user.id
})
user_email:save()
-- Not save!

-- And try again
local user_email = UserEmails({
    email = "mail@example.com",
    user_id = user.id
})
user_email:save()
-- This email added!
    
user_email.email = "not email"
user_email:save()
-- Not update
    
user_email.email = "valid@email.com"
user_email:save()
-- Update!

Corona SDK support

Will be implemented ...

Final

All code you can see in example.lua file. Feel free to use it! Good luck!