How to Install and setup SQL Developer?

SQL Developer

For testing and running SQL statements, SQL Developer is a graphical user interface (GUI) application. Unlike command-line tools like SQLPlus, it features a user-friendly interface that has helped it gain a lot of traction with developers. Database managers frequently utilise SQLPlus, a fundamental command-line tool that comes with every Oracle Database installation, but SQL Developer provides a visual interface for database interaction. Because graphical interfaces like Oracle SQL Developer are becoming more and more popular, frequently leaves out SQLPlus prompts from examples that are not specifically for SQLPlus. With Oracle 11g, SQL Developer is also one of the components that comes pre-installed.

Installing and Configuring SQL Developer

SQL Developer must to be downloaded and installed before you can begin using it. For educational reasons, the Oracle Technology Network (OTN) offers the software needed to install Oracle Database at no cost. The OTN website (http://www.oracle.com/technology/index.html) provides product details, documentation, and free downloads. Installing the sample schemas that come with Oracle 11g is advised in order to have test data while using tools like as GoldenGate. This recommendation also applies to SQL Developer for practice.

SQL Developer has integrated unit testing functionality and is built to be more resilient.

Connecting to a Database and Exploring Objects

After installation, connecting to a database is an essential next step. You can visually explore database objects in SQL Developer once a connection has been made. Using a graphical interface instead of using command-line scripts to query data dictionary views such as ALL_OBJECTS or USER_OBJECTS makes navigation easier.

Your First SQL Query

When using SQL to communicate with an Oracle database, it is customary to start by running a quick query to verify connectivity and comprehension. The statement SELECT 'Hello world!' FROM dual; is often used for this purpose.

Here’s how you might enter and execute this in SQL Developer (or SQL*Plus):

Code:

SELECT 'Hello world!' FROM dual;

Code Output:

'HELLOWORLD!'
-------------
Hello world!

This SELECT statement tells Oracle to retrieve information. Specifically, SELECT 'Hello world!' indicates that you want to display the literal string ‘Hello world!’. The FROM dual clause specifies the table from which to retrieve this information. In Oracle, SELECT is a Data Manipulation Language (DML) statement used for retrieving data. Every SELECT query requires both the SELECT and FROM keywords.

The DUAL Table

Often called a “convenience table,” the dual table is a unique table in Oracle. It’s included in the data dictionary. Its main feature is that there is only one row and one column. The value of the single column, usually called DUMMY, is ‘X’.

For rapid testing and calculations where you want to obtain a single answer from the database rather than retrieve data from a particular application table, the dual table is immensely helpful. Dual, for instance, can be used to display random text inside a SQL script, retrieve the current system date, and do out mathematical operations.

Here are a couple of examples of using the dual table for quick tests and calculations:

Retrieving the current operating system date and time: Code:

SELECT SYSDATE FROM dual;

Code Output (example, date/time will vary):

SYSDATE
---------
23-OCT-24

(SYSDATE is an Oracle function that returns the current date and time of the database server.)

Performing a simple arithmetic calculation: Code:

SELECT 34 * 0.15 FROM dual;

Code Output:

   34*0.15
----------
       5.1

By enabling single-row queries for a variety of functions, computations, or just to retrieve a single value, the dual table essentially serves as an Oracle database scratchpad, eliminating the need to access bigger, more intricate data tables. Anybody working with Oracle SQL should understand this basic idea since it offers a straightforward and dependable method of testing expressions and procedures.

Comparable to a single-sheet calculator is the dual table. You can quickly calculate or check the current date by typing your expression into this single-row “calculator” and get an instant result, eliminating the need to open an entire spreadsheet or database.