Expression in assignment statement - pl sql, PL-SQL Programming

Expression:

This is a randomly complex combination of constants, variables, literals, operators, & function calls. The simplest expression consists of a single variable. If the assignment statement is executed, the expression is computed and the resulting value is stored in the assignment target. The value and target must have well-suited datatypes.

By default, unless the variable is initialized in its declaration, it is initialized to NULL every time a subprogram or block is entered. Therefore, never reference a variable before you assign it a value. You can't assign nulls to a variable defined as NOT NULL. If you attempt, the PL/SQL raises the predefined exception VALUE_ERROR. The values TRUE, FALSE, & NULL can also be assigned to a Boolean variable. If applied to an expression, the relational operators return a Boolean value. And hence, the assignment below is legal:

DECLARE

out_of_range BOOLEAN;

...

BEGIN

...

out_of_range := (salary < minimum) OR (salary > maximum);

As the later illustration shows, you can assign the value of an expression to an  explicit field in a record:

DECLARE

emp_rec emp%ROWTYPE;

BEGIN

...

emp_rec.sal := current_salary + increase;

Furthermore, you can assign values to all the fields in a record at once. The PL/SQL permits an aggregate assignment between the whole records if their declarations refer to similar cursor or table. For illustration, the assignment below is legal:

DECLARE

emp_rec1 emp%ROWTYPE;

emp_rec2 emp%ROWTYPE;

dept_rec dept%ROWTYPE;

BEGIN

...

emp_rec1 := emp_rec2;

The later assignment is illegal as you cannot use the assignment operator to assign the list of values to a record:

dept_rec := (60, 'PUBLICITY', 'LOS ANGELES');

Using the syntax below, you can assign the value of an expression to the specific element in a collection:

collection_name(index) := expression;

In the example below, you assign the uppercase value of the last_name to the third row in nested table ename_tab:

ename_tab(3) := UPPER(last_name);

Posted Date: 10/6/2012 8:45:37 AM | Location : United States







Related Discussions:- Expression in assignment statement - pl sql, Assignment Help, Ask Question on Expression in assignment statement - pl sql, Get Answer, Expert's Help, Expression in assignment statement - pl sql Discussions

Write discussion on Expression in assignment statement - pl sql
Your posts are moderated
Related Questions
Raise_application_error -  procedure of package DBMS_STANDARD , allows to issue an user_defined error messages by stored sub-program or database trigger.

Example of GROUPBY Operator Example: How many students sat each exam, using GROUP BY, NATURAL LEFT JOIN, and COALESCE SELECT CourseId, COALESCE (n, 0) AS n FROM COURS

Consider the schema for FreeChecking Bank, that we designed given below. Translate the given ER schema into SQL CREATE TABLE statements (indicating primary key, unique and foreign

Relational Operators The relational operators permit you to compare randomly complex expressions. The list below provides the meaning of each operator:

Cursor Variables:   To execute the multi-row query, the Oracle opens an unnamed work region that stores the processing information. You can use an explicit cursor that names

Attributes: Just similar to variable, an attribute is declared with a name and datatype. The name should be exclusive within the object type. The datatype can be any Oracle ty

Creating a Table Syantax: CREATE TABLE ENROLMENT (StudentId SID, Name   VARCHAR (30) NOT NULL, CourseId CID, PRIMARY KEY (StudentId, CourseId)) ; Explan

V ariables and Constants in PL/SQL The PL/SQL permits you to declare constants and variables, and then use them in SQL and procedural statements anywhere in the expression. Th

Declaring Subprograms   You can declare subprograms in any PL/SQL subprogram, block, or package. But, you should declare subprograms at the end of the declarative part after a

Restriction in SQL Syntax: SELECT DISTINCT StudentId FROM IS_CALLED WHERE Name = 'Boris' The WHERE clause operates on the result of the FROM clause in analogo