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

Assignment Help:

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);


Related Discussions:- Expression in assignment statement - pl sql

Some varray examples-manipulating collections, Some Varray Examples In S...

Some Varray Examples In SQL Plus, assume that you define an object type Project, as described below: SQL> CREATE TYPE Project AS OBJECT ( 2 project_no NUMBER(2), 3 title VARCHA

Example of except operator - sql, Example of EXCEPT Operator - SQL Ex...

Example of EXCEPT Operator - SQL Example, like its counterpart in the theory book, illustrates the convenience of allowing any table expression to be the source for an INSERT

Initializing objects in pl sql, Initializing Objects: Till you initiali...

Initializing Objects: Till you initialize an object by calling the constructor for its object type, the object is automatically null. That is, the object itself is null, not me

Use external routines - improve performance of application, Use External Ro...

Use External Routines The PL/SQL is particular for the SQL transaction processing. Therefore, several tasks are more quickly completed in a lower-level language like C that is

Declaring a cursor, Declaring a Cursor The Forward references are not ...

Declaring a Cursor The Forward references are not allowed in the PL/SQL. Therefore, you must declare a cursor before referencing it in other statements. Whenever you declare a

Select into statement - syntax, SELECT INTO Statement   The SELECT INT...

SELECT INTO Statement   The SELECT INTO statement retrieve data from one or more database tables, and then assigns the selected values to the variables or fields. Syntax:

Deriving predicates from predicates in sql, Deriving Predicates from Predic...

Deriving Predicates from Predicates in SQL The corresponding section in the theory book describes how predicates can be derived from predicates using (a) the logical connectiv

Full time system administrator, Need Windows and Linux system Administrator...

Need Windows and Linux system Administrator We are seeking a part time system administrator to take care of our servers. Your things to do would add, but not limited to: -

Close statement in pl sql, CLOSE Statement The CLOSE statement allows ...

CLOSE Statement The CLOSE statement allows the resources held by a cursor variable or open cursor to be reused. No more rows can be fetched from the cursor variable or closed

Using count, Using COUNT The COUNT returns the number of elements that...

Using COUNT The COUNT returns the number of elements that a collection presently contains. For instance, when a varray projects contains 15 elements, then the following IF con

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd