Constants and variables in pl sql, PL-SQL Programming

Constants and Variables:

 You can declare the constants and variables in the declarative section of any PL/SQL subprogram, block, or package. The Declarations allot the storage space for a value that specify its datatype, and name the storage space location so that you can reference it. The Declarations can also assign an initial value and enforce the NOT NULL constraint.

1070_constant variable.png

Keyword and Parameter Description:

constant_name:

These identify the program constant.

CONSTANT:

These keywords indicate the declaration of a constant. You should initialize a constant in its declaration. The value of a constant cannot be changed if once it is initialized.

record_name.field_name:

These identify the field in a user-defined or %ROWTYPE record formerly declared within the present scope.

scalar_type_name:

These identify a predefined scalar datatype like the BOOLEAN, NUMBER, or VARCHAR2.

db_table_name.column_name:

These identify a database table and column that should be available when the declaration is elaborated.

variable_name:

These identify the program variable.

collection_name:

These identify the nested table, index-by table, or varray earlier declared within the present scope.

cursor_name:

These identify an explicit cursor formerly declared within the present scope.

cursor_variable_name:

These identify a PL/SQL cursor variable formerly declared within the present scope.

object_name:

These identify an object (or instance of the object type) formerly declared within the present scope.

record_name:

These identify a user-defined record formerly declared within the present scope.

db_table_name:

These identify a database table (or view) that should be available when the declaration is elaborated.

%ROWTYPE:

This attribute gives a record type that presents a row in the database table or a row fetched from a formerly declared cursor. The Fields in the record and corresponding columns in the row have similar names and datatypes.

%TYPE:

This attribute gives the datatype of a formerly declared collection, field, cursor variable, object, record, database column, or variable.

NOT NULL:

These constraints prevent the assigning of the nulls to a variable or constant. At run time, trying to assign the null to a variable defined as NOT NULL raises the predefined exception VALUE_ERROR. The constraint NOT NULL should be followed by an initialization clause.

Expression:

This is a randomly complex combination of the variables, literals, constants, operators, and function calls. The easiest expression consists of a single variable. If the declaration is elaborated, the value of the expression is assigned to the constant or variable. The value and the constant or variable should have compatible datatypes.

Posted Date: 10/6/2012 9:10:04 AM | Location : United States







Related Discussions:- Constants and variables in pl sql, Assignment Help, Ask Question on Constants and variables in pl sql, Get Answer, Expert's Help, Constants and variables in pl sql Discussions

Write discussion on Constants and variables in pl sql
Your posts are moderated
Related Questions
3CX PBX sync Windows Service Project Description: !! You require access to a commercial version of the 3CX PBX system in order to be able to program the API !! !! You requ

Cursor Attributes   The Cursors and cursor variables have 4 attributes which give you helpful information about the execution of a data manipulation statement. Syntax:

Package STANDARD package named STANDARD defines the PL/SQL atmosphere. The package specification globally declares the exceptions, types, and subprograms that are available a

Varrays versus Nested Tables The Nested tables are differing from varrays in the following ways: 1)  Varrays have a maximum size, while nested tables do not. 2)  Varrays are

What are 3 good practices of modeling and/or implementing data warehouses?

%TYPE Attribute The %TYPE attribute gives the datatype of a record, field, nested table, database column, or the variable. You can use the %TYPE attribute as the datatype speci

Keyword & Parameter Description: PRAGMA: These keywords signify that the statement is a pragma (i.e. compiler directive). The Pragmas are processed at the compile time, n

Procedural Constraint Enforcement (Triggers) SQL has an alternative method of addressing database integrity, involving event-driven procedural code. The special procedures th

Example of WRAP Operator - SQL The effect of Example can be obtained in SQL but note that one needs to write down not only the names of the columns being wrapped but also the

ROWNUM The ROWNUM returns a number representing the order in which a row was selected from the table. The first row selected has a ROWNUM of 1; the second row has a ROWNUM of