Chapter 1. Declaring Variables and Naming Elements
Variables allow you to store and manipulate data—such as column values, counters, or calculations—inside your PL/SQL programs. There are two types of variables: scalar, which are made up of a single value, and composite, which are made up of multiple pieces (a record, for example, is represented with a composite variable). Whether composite or scalar, every variable has a name (also called an identifier), a datatype (such as NUMBER or VARCHAR2), and a value. This chapter tests your ability to work with these most basic PL/SQL elements.
1-1. | Which of the following identifiers are valid, which are invalid, and why? my_variable2
my-variable2
my^variable
MyVariable
my_variable_for_many_many_of_usages
123myvariable
“123myvariable”
|
1-2. | Which of the following blocks will compile, and which will fail to compile? Why? DECLARE
lastdate DATE;
lastDate NUMBER;
BEGIN
NULL;
END; DECLARE
lastdate DATE := sysdate;
lastDate NUMBER := 50;
BEGIN
dbms_output.put_line(lastdate);
dbms_output.put_line(lastDate);
END;
|
1-3. | Declare a date variable with an initial value of SYSDATE (show both valid formats). |
1-4. | Declare a local variable to have the same datatype as the last_name column in the employee table. |
1-5. | Explain what is wrong with each of the following declarations: DECLARE
INTEGER year_count;
VARCHAR2(100) company_name, employee_name;
delimiters VARCHAR2;
curr_year CONSTANT INTEGER;
invalid_date EXCEPTION := VALUE_ERROR; |
1-6. | What datatype is most appropriate to store the following data items? 'This is a test'
Values from 1 to 10
5.987
'This is a test '
A string that is always nine characters long
January 10, 2000
A binary file
TRUE or FALSE
The internal identifier of a row in a table |
