Posts Tagged ‘1Z0-007’

What is DECODE function?

September 1st, 2009

The DECODE function decodes a column value or an expression and compares it with each specified search value, one by one. If the expression matches a search value, a result value corresponding to the matching search value is returned. If no match is found, a default result value, if included, is returned. However, if no default value is included, a NULL value is returned. The DECODE function is one of the few single-row functions that directly deal with NULL values. It can compare two NULL values and can return a NULL value.

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What is TO_CHAR (datetime) function?

September 1st, 2009

TO_CHAR (datetime) is a single-row function that is used to convert a value of DATE, TIMESTAMP, TIMESTAMP WITH TIME ZONE, or TIMESTAMP WITH LOCAL TIME ZONE datatype to a value of VARCHAR2 datatype in the specified date format.

Syntax:

TO_CHAR ( datetime [, fmt [, 'nlsparam' ]] )

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What is system privilege?

July 15th, 2009

System privilege is a privilege or right that allows a user to perform system level activities, such as connecting to a database, creating, altering, dropping, and managing database objects or features. Oracle does not retain the grantor of the system privileges. Therefore, even if a grantee has obtained system privileges from more than one grantor, these can be revoked by anyone with the appropriate privileges.

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What is the syntax for creating a view?

July 15th, 2009

Following is the syntax for creating a view:

CREATE [OR REPLACE] [FORCE | NOFORCE] VIEW ViewName
[ (alias [, alias]…) ]
AS subquery
[WITH { READ ONLY | CHECK OPTION [CONSTRAINT ConstraintName] }];

where,

  • OR REPLACE re-creates a pre-existing view with the new specified definition.
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    When is top-n analysis performed?

    July 15th, 2009

    Top-n analysis is performed when the n topmost or the n bottommost records from a table are to be displayed. For example, top-n analysis can be performed in the following conditions:

  • To display the top three scorers in a subject.
  • To display the top five earners in a company.
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    What is a Cartesian product?

    July 15th, 2009

    A join, between two or more tables, with no join condition results in a Cartesian product. A Cartesian product is a set of all possible combinations of rows drawn from each table involved in the join. In other words, Oracle combines each row of one table with each row of the other table. For example, the Cartesian product of two tables with five rows each, has twenty-five rows.

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    What is IS NOT NULL operator?

    July 15th, 2009

    IS NOT NULL is a comparison operator that is used to compare a value with a NULL value. It evaluates to TRUE if the value is not NULL, otherwise it evaluates to FALSE.

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    What is DML?

    July 12th, 2009

    Data Manipulation Language (DML) is a category of SQL statements that query and update data in a database. Statements such as SELECT, UPDATE, INSERT, DELETE etc., are included in this category. These statements can be grouped with Data Control Language (DCL) statements.

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    What is a tablespace?

    July 10th, 2009

    A tablespace is a logical database structure for storing database segments. By default, each Oracle database has a single tablespace, known as SYSTEM, which stores data dictionary tables and indexes. Other tablespaces may also be configured for a database for performing some specific tasks such as:

    • Partial backup and recovery operation
    • Allocation of quotas for users

    Additional tablespaces can also be created as per the requirements of the applications installed on the system. Such tablespaces can be used for storing application specific segments.

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    What is DECODE function?

    July 8th, 2009

    The DECODE function decodes a column value or an expression and compares it with each specified search value, one by one. If the expression matches a search value, a result value corresponding to the matching search value is returned. If no match is found, a default result value, if included, is returned. However, if no default value is included, a NULL value is returned. The DECODE function is one of the few single-row functions that directly deal with NULL values. It can compare two NULL values and can return a NULL value.

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