Creating an Oracle Database Connection

Database connections can be created and saved for reuse. Figure below shows the window where connections can be defined. To reach this window, click the “+” symbol visible on the Connections tab. The username and password must both be supplied, but only the username will be saved unless the Save Password check box is selected. Saving a password means that future connections can be made without any password prompt. This is convenient but highly dangerous if there is any possibility that the computer you are working on is not secure. In effect, you are delegating the authentication to your local operating system: if you can log on to that, you can log on to the database.

The Connection Type radio buttons let you choose between three options:

• Basic This prompts for the machine name of the database server, the port on which the database listener will accept connection requests, and the instance (the SID) or the service to which the connection will be made.
• TNS If a name resolution method has been configured, then an alias for the database can be entered, rather than the full details needed by the Basic option.
• Advanced This allows entry of a full JDBC (Java Database Connectivity) connect string. This is completely Oracle independent and could be used to connect to any database that conforms to the JDBC standard.

Selecting Basic requires the user to know how to connect to the database; selecting TNS requires some configuration to have been done on the client machine by the database administrator, in order that the alias can be resolved into the full connection details.

After you enter the details, the Test button will force SQL Developer to attempt a logon. If this returns an error, then either the connection details are wrong, or there is a problem on the server side. Typical server-side problems are that the database listener is not running, or that the database has not been started. Whatever the error is, it will be prefixed with an error number.

SQL Developer

SQL Developer

SQL Developer is a tool for connecting to an Oracle database (or, in fact, some non-Oracle databases too) and issuing ad hoc SQL commands. It can also manage PL/SQL objects. Unlike SQL*Plus, it is a graphical tool with wizards for commonly needed actions. SQL Developer is written in Java and requires a Java Runtime Environment (JRE) to run. Being written in Java, SQL Developer is available on all platforms that support the appropriate version of the JRE. There are no significant differences between platforms.

The general layout of the SQL Developer window is a left pane for navigation around objects, and a right pane to display and enter information. In the figure, the left-hand pane shows that a connection has been made to a database. The connection is just a label chosen when the connection was defined, but most developers will use some sort of naming convention. The branches beneath list all the possible object types that can be managed. Expanding the branches would list the objects themselves. The right-hand pane has an upper part prompting the user to enter a SQL statement and a lower part that will display the result of the statement. The layout of the panes and the tabs visible on them are highly customizable.
The menu buttons across the top menu bar give access to standard facilities:

• File A normal Windows-like file menu, from which one can save work and exit from the tool.
• Edit A normal Windows-like edit menu, from which one can undo, redo, copy, paste, find, and so on.
• View The options for customizing the SQL Developer user interface.
• Navigate Facilities for moving between panes and for moving around code that is being edited.
• Run Forces execution of the SQL statements, SQL script, or PL/SQL block that is being worked on.
• Debug Rather than running a whole block of code, steps through it line by line with breakpoints.
• Source Options for use when writing SQL and PL/SQL code, such as keyword completion and automatic indenting.
• Tools Links to external programs, including SQL*Plus.
• Migrate Tools for converting applications designed for third-party databases (Microsoft Access, SQL Server, and MySQL) to the Oracle environment.
• Help It’s pretty good.

SQL Developer can be a very useful tool, and it is very customizable. Experiment with it, read the Help, and set up the user interface the way that works best for you.

Reference:

• OCA Oracle Database 11g: SQL Fundamentals I Exam Guide (Exam 1Z0-051)