Node.js MySQL LEFT() Function

LEFT() Function is a Builtin function in MySQL which is used to get Prefix of a specific size of Given String.

Syntax:

LEFT(input_string, size_of_prefix)

Parameters: LEFT() function accepts two parameters as mentioned above and described below.

• input_string: We will get prefix of this input string
• size_of_prefix: Number of characters in the prefix

Return Value: LEFT() function returns a string which is a prefix of input_string of specific size.

Modules:

• mysql: To handle MySQL Connection and Queries

npm install mysql

SQL publishers Table Preview:

Example 1: Static Query

Javascript

const mysql = require("mysql");

let db_con = mysql.createConnection({
  host: "localhost",
  user: "root",
  password: "",
  database: "gfg_db",
});

db_con.connect((err) => {
  if (err) {
    console.log("Database Connection Failed !!!", err);
    return;
  }

  console.log("We are connected to gfg_db database");

  // here is the query
  let query = "SELECT LEFT(name, 4) AS prefix_name FROM publishers";

  db_con.query(query, (err, rows) => {
    if (err) throw err;

    console.log(rows);
  });
});

Output:

Example 2: Dynamic Query

Javascript

const mysql = require("mysql");

let db_con = mysql.createConnection({
  host: "localhost",
  user: "root",
  password: "",
  database: "gfg_db",
});

db_con.connect((err) => {
  if (err) {
    console.log("Database Connection Failed !!!", err);
    return;
  }

  console.log("We are connected to gfg_db database");

  // notice the ? in below query
  let query = "SELECT LEFT(salary, ?) AS prefix_salary FROM publishers";
  let sizeOfPrefix = 3;

  // notice second argument in below function
  db_con.query(query, sizeOfPrefix, (err, rows) => {
    if (err) throw err;

    console.log(rows);
  });
});

Output: