How to access oralce in nodejs

Node.js is a very popular JavaScript runtime environment that enables server-side programming. It is very fast and flexible compared to other languages ​​and has the ability to handle I/O intensive tasks. In addition to this, Node.js also excels when interacting with databases. In this article, we will learn how to access and operate Oracle database using Node.js.

Before using Node.js to connect to the Oracle database, we need to ensure that the following has been installed:

• Node.js
• Oracle Instant Client
• Oracledb module of Node.js

1. Install Oracle Instant Client

Oracle Instant Client is a lightweight client for Oracle database that can be used Access the database from Node.js. When installing Oracle Instant Client, be sure to select a version that is compatible with your operating system and Oracle database version. You can download Oracle Instant Client from the Oracle website, or install it using the command:

$ sudo apt-get install libaio1
$ wget https://download.oracle.com/otn_software/linux/instantclient/1912000/oracle-instantclient19.12-basic-19.12.0.0.0-1.x86_64.rpm
$ sudo alien -i oracle-instantclient19.12-basic-19.12.0.0.0-1.x86_64.rpm

2. Install the oracledb module for Node.js

In order to access the Oracle database using Node.js, We need to use oracledb module. To install the oracledb module, navigate to your project folder in the console and run the following command:

$ npm install oracledb

3. Create a JavaScript file that connects to the Oracle database

To connect Oracle database, we need to use information about Oracle connection. This information is usually located in the tnsnames.ora file. The tnsnames.ora file contains the connection information for the Oracle database you want to connect to. If you do not know the location of the tnsnames.ora file, please contact your Oracle administrator to inquire.

In your project folder, create a file called dbconfig.js and add the following content in it:

module.exports = {
 user: "用户名",
 password: "密码",
 connectString: "连接字符串"
}

Please use your Oracle username, password and connection character String replaces the string value in the above code.

4. Connecting to Oracle Database

Now, we are ready to connect to Oracle database and perform some operations. To do this, create a JavaScript file and then do the following:

const oracledb = require('oracledb');
const dbConfig = require('./dbconfig.js');

oracledb.getConnection(
 {
  user: dbConfig.user,
  password: dbConfig.password,
  connectString: dbConfig.connectString
 },
 function(err, connection)
 {
  if (err) {
   console.error(err.message);
   return;
  }
  console.log('Connection was successful!');

  connection.close(
   function(err) {
    if (err) {
     console.error(err.message);
     return;
    }
    console.log('Connection was closed!');
   });
 });

By executing the above code, we can connect to the Oracle database. We use the oracledb.getConnection method to connect to the database. If the connection fails, an error message is output, otherwise a successful connection message is output. Then we close the connection using the connection.close method.

5. Execute queries

Once connected to the database, we can perform operations such as queries, additions, deletions, modifications, etc. To execute the query, add the following code to the JavaScript file from the previous step:

const oracledb = require('oracledb');
const dbConfig = require('./dbconfig.js');

oracledb.getConnection(
 {
  user: dbConfig.user,
  password: dbConfig.password,
  connectString: dbConfig.connectString
 },
 function(err, connection)
 {
  if (err) {
   console.error(err.message);
   return;
  }
  console.log('Connection was successful!');

  connection.execute(
   `SELECT empno, ename FROM emp`,
   function(err, result) {
    if (err) {
     console.error(err.message);
     return;
    }
    console.log(result.rows);
    connection.close(
     function(err) {
      if (err) {
       console.error(err.message);
       return;
      }
      console.log('Connection was closed!');
     });
   });
 });

In the above code, we use the connection.execute method to execute the query. If the query fails, an error message is printed, otherwise a row of query results is printed.

Summary

This article introduces how to use Node.js to access Oracle database. We first install Oracle Instant Client and the oracledb module of Node.js, then create a JavaScript file to connect to the Oracle database, then connect to the database and execute the query. One of the advantages of using Node.js with Oracle Database is its performance: Node.js is well-suited for handling I/O-intensive tasks and high concurrency, so it also performs well when used with Oracle Database.

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