Tag Archives: SQL
How to Change Password in Oracle ?
You can change your Oracle login password using the Change Password page. Changing your password regularly reduces the risk of someone obtaining your password and gaining unauthorized access to your account. You must specify your username, old password, and your … Continue reading
Script Formatting and System Variables in Oracle
Executing a script and formatting its output are controlled by system variables. A system variable in iSQL*Plus is similar to a variable in any programming language. Like a column in a row of a table, a system variable can hold … Continue reading
iSQL*Plus Configuration
After logging in Oracle database using the iSQL*Plus login screen, you can make changes to your environment using the Preferences link in the upper-right area of the browser. From the Preferences screen, you can do one of five things: … Continue reading
NULLs: What, When, Why, and How ?
NULL value in an Oracle table is nothing. A NULL is neither zero, a blank character, or an empty string. NULLs can be the source of much consternation when a query is not returning the expected results. NULL :- A … Continue reading
The DUAL Table in Oracle
Because Oracle SQL is table-centric, most operations performed with SQL must reference some kind of table or view. For example, consider the following SQL statement: SELECT NAME; SELECT NAME * ERROR at line 1: ORA-00923: … Continue reading
Subqueries
A subquery places one query inside another one. The second query resides somewhere within the WHERE clause of a SELECT statement. One or more values returned by the subquery are used by the main query to return the results to … Continue reading
Join Syntax in Oracle
So far, we have been dealing with only one table at a time in our SQL query examples. But typically the information needed to satisfy a user query requires more than one table. In new SQL 1999, you can not … Continue reading
SQL*Plus Worksheet
Oracle Enterprise Manager (OEM) : A GUI tool that allows access, maintenance, and monitoring of multiple databases or services within a single application. If Oracle Enterprise Manager (OEM) is installed, another variation of SQL*Plus, called SQL*Plus Worksheet, is available to the … Continue reading
iSQL*Plus
With iSQL*Plus, you connect to the database indirectly via a very “lightweight” middle tier. The iSQL*Plus tool is essentially the web-enabled version of SQL*Plus, with a few restrictions, which we will cover shortly. It is implemented as part of … Continue reading
SQL*Plus
SQL*Plus has been around as long as the Oracle RDBMS itself. It is the most basic tool available for connecting to the database and executing queries against the tables in a database. On Unix systems, it can be run in … Continue reading
Implementing Data Integrity
If checks are not applied while defining and creating tables, the data stored in the tables can become redundant. For example, if you do not store the data about all the employees with complete address details, then the data would … Continue reading
System Databases in SQL Server 2005
System Databases are the standard databases that exist in every instance of SQL Server 2005.These databases contain a specific set of tables that are used to store server- specific configurations, templates for other databases. In addition, these databases contain a … Continue reading