joins.js

import React from 'react';
import SQLite from 'react-native-sqlite-storage';

export default class SQLiteScreen extends React.Component {
  constructor() {
    super();
    SQLite.DEBUG = true;
  }

  /**
  * Execute sql queries
  * 
  * @param sql
  * @param params
  * 
  * @returns {resolve} results
  */
  ExecuteQuery = (sql, params = []) => new Promise((resolve, reject) => {
    db.transaction((trans) => {
      trans.executeSql(sql, params, (trans, results) => {
        resolve(results);
      },
        (error) => {
          reject(error);
        });
    });
  });

  //**
   * Joins Example
   */
  async JoinsQuery() {
    // INNER JOIN
    let innerJoin = await this.ExecuteQuery("SELECT users.id, users.first_name, users.last_name, c.country_name FROM users INNER JOIN country c on c.user_id = users.id", []);
    var rows = innerJoin.rows;
    for (let i = 0; i < rows.length; i++) {
      var item = rows.item(i);
      console.log(item);
    }
    console.log(innerJoin);

    // LEFT JOIN
    let leftJoin = await this.ExecuteQuery("SELECT users.id, users.first_name, users.last_name, c.country_name FROM users LEFT JOIN country c on c.user_id = users.id", []);
    var rows = leftJoin.rows;
    for (let i = 0; i < rows.length; i++) {
      var item = rows.item(i);
      console.log(item);
    }
    console.log(leftJoin);

    // RIGHT JOIN
    let rightJoin = await this.ExecuteQuery("SELECT users.id, users.first_name, users.last_name, c.country_name FROM users RIGHT JOIN country c on c.user_id = users.id", []);
    var rows = rightJoin.rows;
    for (let i = 0; i < rows.length; i++) {
      var item = rows.item(i);
      console.log(item);
    }
    console.log(rightJoin);

    // FULL OUTER JOIN
    let fullOutterJoin = await this.ExecuteQuery("SELECT users.id, users.first_name, users.last_name, c.country_name FROM users FULL OUTER JOIN country c on c.user_id = users.id", []);
    var rows = fullOutterJoin.rows;
    for (let i = 0; i < rows.length; i++) {
      var item = rows.item(i);
      console.log(item);
    }
    console.log(fullOutterJoin);

  }

}