Query Language

The query language is based on javascript lambda expression. These Queries can be written as javascript code by browsing the business model entities.

Queries can also be sent as a string

λOrm translates the query into the language corresponding to each database engine.

Queries type

DQL

Las consultas DQL (Data Query Language) son consultas utilizadas para recuperar datos de una base de datos.

Las consultas DQL pueden ser bastante simples o pueden incluir cláusulas adicionales para filtrar, ordenar o agrupar datos, así como para realizar cálculos y operaciones en los datos recuperados. Esto permite a los desarrolladores obtener los datos exactos que necesitan de una base de datos según los requisitos de la aplicación.

View: Select Join Grouping Include

DML

DML (Data Manipulation Language) queries are used to manipulate data in a database. Mainly, they include the following operations:

  • INSERT: Used to add new records to a table.
  • UPDATE: Used to modify existing records in a table.
  • DELETE: Used to delete records from a table.

View: Insert BulkInsert Update Delete

DDL

DDL (Data Definition Language) are used to define, modify and delete database structures and related objects. Mainly, they include the following operations:

  • CREATE: Used to create new objects in the database, such as tables, indexes, views and other objects.
  • ALTER: Used to modify the structure of existing objects in the database, such as adding, modifying or deleting columns from a table, changing the data type of a column, renaming an object, among others.
  • DROP: Used to delete database objects, such as tables, indexes, views and other objects.

These queries are created and executed when you use the schema synchronization commands.

View: Push Pull Fetch Introspect Incorporate

Example:

// Selecting countries filtering by region and including related states starting with 'F', with pagination
Countries
    .filter(p=> p.region == region) 
    .map(p=> [p.name,p.subregion,p.latitude,p.longitude]) // Selecting country fields
    .include(p => p.states.filter(p=> substr(p.name,1,1)=="F") // Including states starting with 'F'
          .map(p=> [p.name,p.latitude,p.longitude])
    )
    .page(1,3) // Pagination for countries, 3 records per page

where the SQL equivalent of the query is:

-- Selecting countries based on region and limiting to 3 records
SELECT c.name AS `name`, c.subregion AS `subregion`, c.latitude AS `latitude`, c.longitude AS `longitude`, c.iso3 AS `__iso3` 
FROM Countries c  
WHERE c.region = ? 
LIMIT 0,3

-- Selecting states starting with 'F' belonging to the specified countries
SELECT s.NAME AS "name", s.LATITUDE AS "latitude", s.LONGITUDE AS "longitude", s.COUNTRY_CODE AS "__parentId" 
FROM TBL_STATES s  
WHERE SUBSTR(s.NAME,1,1) = 'F'
  AND s.s.COUNTRY_CODE IN (?)

Advantage of Query Language

  • Use of the same programming language.
  • No need to learn a new language.
  • queries easy to write and understand.
  • Use of the intellisense offered by the IDE to write the expressions.
  • Avoid syntax errors.