Getting the current Oracle version (via a SQL Select query):

how to check the version of oracle database in sql developer :

https://docs.oracle.com/cd/E17781_01/server.112/e18804/dbconfig.htm#ADMQS253

You can use SQL Developer to view the database version information and national language support (globalization) settings.

This section contains the following topics:

• Viewing Database Version Information
• Viewing Database Globalization Information

Viewing Database Version Information

To view database version information:

1. In SQL Developer, click the Reports tab on the left, near the Connections navigator. (If this tab is not visible, click View, then Reports.)
2. In the Reports navigator, expand Data Dictionary Reports.
3. Under Data Dictionary Reports, expand About Your Database.
4. Under About Your Database, click Version Banner.
   The Version Banner report is displayed, as shown in Figure 9-1.

   Viewing Database Globalization Information

   To view database globalization (national language support, or NLS) parameter information:
   1. In SQL Developer, click the Reports tab on the left, near the Connections navigator. (If this tab is not visible, click View, then Reports.)
   2. In the Reports navigator, expand Data Dictionary Reports.
   3. Under Data Dictionary Reports, expand About Your Database.
   4. Under About Your Database, click National Language Support Parameters.
      The National Language Support Parameters report is displayed, as shown in Figure 9-1.
      Figure 9-2 National Language Support Parameters Report

https://community.oracle.com/thread/2250946

http://stackoverflow.com/questions/101184/how-can-i-confirm-a-database-is-oracle-what-version-it-is-using-sql

You can try:

SELECT * FROM V$VERSION

select * from v$version;

Result:

Oracle Database 10g Enterprise Edition Release 10.2.0.2.0 - Prod
PL/SQL Release 10.2.0.2.0 - Production
"CORE 10.2.0.2.0 Production"
TNS for Linux: Version 10.2.0.2.0 - Production
NLSRTL Version 10.2.0.2.0 - Production

or

Getting the current Oracle version (via a SQL Select query):

select *
from v$version;

select *
from product_component_version;
Result:
Product                                 Version         Status
NLSRTL                                  10.2.0.2.0 Production
Oracle Database 10g Enterprise Edition  10.2.0.2.0 Prod
PL/SQL                                  10.2.0.2.0 Production
TNS for Linux:                          10.2.0.2.0 Production

or

BEGIN DBMS_OUTPUT.PUT_LINE(DBMS_DB_VERSION.VERSION || '.' || DBMS_DB_VERSION.RELEASE); END;

======

select from v$version;*

This will give you detailed version number of the database components. You can also use 

select from PRODUCT_COMPONENT_VERSION;*

to get various components of the DB with their version.