uCertify Articles » 1Z0-007 http://www.ucertify.com/article Just another WordPress weblog Wed, 04 Nov 2009 00:00:00 +0000 http://wordpress.org/?v=2.8.4 en hourly 1 What is DECODE function? http://www.ucertify.com/article/what-is-decode-function-2.html http://www.ucertify.com/article/what-is-decode-function-2.html#comments Tue, 01 Sep 2009 00:00:00 +0000 uCertify 1801007

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.

Syntax:

DECODE (ColumnExpression, search, result[, search, result, ...] [, default] )

ColumnExpression, search, and result can be of the CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype.

Share/Bookmark]]> http://www.ucertify.com/article/what-is-decode-function-2.html/feed 0 What is TO_CHAR (datetime) function? http://www.ucertify.com/article/what-is-to_char-datetime-function-2.html http://www.ucertify.com/article/what-is-to_char-datetime-function-2.html#comments Tue, 01 Sep 2009 00:00:00 +0000 uCertify 1801075

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' ]] )

where,

  • datetime specifies a value of DATE, TIMESTAMP, TIMESTAMP WITH TIME ZONE, or TIMESTAMP WITH LOCAL TIME ZONE datatype.

  • fmt specifies the date format in which the converted value is to be displayed.

  • nlsparam specifies the language in which the names and abbreviations of months and days are to be displayed.
    • Share/Bookmark]]>     http://www.ucertify.com/article/what-is-to_char-datetime-function-2.html/feed 0     What is system privilege? http://www.ucertify.com/article/what-is-system-privilege.html http://www.ucertify.com/article/what-is-system-privilege.html#comments Wed, 15 Jul 2009 00:00:00 +0000 uCertify 1801037

    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.

    System privileges are granted using the GRANT statement.

    Syntax:

    GRANT { system_privilege | role | ALL PRIVILEGES }
    [, { system_privilege | role | ALL PRIVILEGES }]…
    TO grantee_clause [IDENTIFIED BY password] [WITH ADMIN OPTION];

    Share/Bookmark]]>     http://www.ucertify.com/article/what-is-system-privilege.html/feed 0     What is the syntax for creating a view? http://www.ucertify.com/article/what-is-the-syntax-for-creating-a-view.html http://www.ucertify.com/article/what-is-the-syntax-for-creating-a-view.html#comments Wed, 15 Jul 2009 00:00:00 +0000 uCertify 1801047

    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.

  • FORCE creates a view regardless of whether or not the base tables exist.

  • NOFORCE creates a view only if the base tables exist.

  • ViewName specifies the name of the view to be created.

  • alias specifies a name for the column selected by the view’s subquery.

  • subquery is a SELECT statement that retrieves data from the base tables.

  • WITH READ ONLY ensures that no DML operation can be performed on the view.

  • WITH CHECK OPTION ensures that only rows accessible to the view can be manipulated.

  • ConstraintName specifies the name of the CHECK constraint.
    • Share/Bookmark]]>     http://www.ucertify.com/article/what-is-the-syntax-for-creating-a-view.html/feed 0     When is top-n analysis performed? http://www.ucertify.com/article/when-is-top-n-analysis-performed.html http://www.ucertify.com/article/when-is-top-n-analysis-performed.html#comments Wed, 15 Jul 2009 00:00:00 +0000 uCertify 1801073

    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.

  • To display the four most recently hired employees in a company.
    • Share/Bookmark]]>     http://www.ucertify.com/article/when-is-top-n-analysis-performed.html/feed 0     What is a Cartesian product? http://www.ucertify.com/article/what-is-a-cartesian-product.html http://www.ucertify.com/article/what-is-a-cartesian-product.html#comments Wed, 15 Jul 2009 00:00:00 +0000 uCertify 1801081

    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.

    Share/Bookmark]]>     http://www.ucertify.com/article/what-is-a-cartesian-product.html/feed 0     What is IS NOT NULL operator? http://www.ucertify.com/article/what-is-is-not-null-operator.html http://www.ucertify.com/article/what-is-is-not-null-operator.html#comments Wed, 15 Jul 2009 00:00:00 +0000 uCertify 1801088

    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.

    Share/Bookmark]]>     http://www.ucertify.com/article/what-is-is-not-null-operator.html/feed 0     What is DML? http://www.ucertify.com/article/what-is-dml.html http://www.ucertify.com/article/what-is-dml.html#comments Sun, 12 Jul 2009 00:00:00 +0000 uCertify 1501031

    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.

    Share/Bookmark]]>     http://www.ucertify.com/article/what-is-dml.html/feed 0     What is a tablespace? http://www.ucertify.com/article/what-is-a-tablespace.html http://www.ucertify.com/article/what-is-a-tablespace.html#comments Fri, 10 Jul 2009 00:00:00 +0000 uCertify 2201048

    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.

    Share/Bookmark]]>     http://www.ucertify.com/article/what-is-a-tablespace.html/feed 0     What is DECODE function? http://www.ucertify.com/article/what-is-decode-function.html http://www.ucertify.com/article/what-is-decode-function.html#comments Wed, 08 Jul 2009 00:00:00 +0000 uCertify 1801007

    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.

    Syntax:

    DECODE (ColumnExpression, search, result[, search, result, ...] [, default] )

    ColumnExpression, search, and result can be of the CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype.

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