An expression that selects a result and returns it into a variable.

Shows the results of all possible combinations of two conditions.

A block of code that performs actions based on conditional tests.

Write a PL/SQL block:

A. To find the number of airports from the countries table for a supplied country_name. Based on this number, display a customized message as follows:

# Airports	Message
0100	There are 100 or fewer airports.
1011,000	There are between 101 and 1,000 airports.
10011,0000	There are between 1,001 and 10,000 airports.
> 10,000	There are more than 10,000 airports.
No value in database	The number of airports is not available for this country.

Use a CASE statement to process your comparisons.

You can use the following code to get started:

DECLARE

v_country_name countries.country_name%TYPE := ''; v_airports countries.airports%TYPE;

BEGIN

SELECT airports INTO v_airports

FROM wf_countries

WHERE country_name = v_country_name;

CASE

WHEN ...

END CASE;

END;

Write a PL/SQL block:

A. To find the number of airports from the countries table for a supplied country_name. Based on this number, display a customized message as follows:

# Airports	Message
0100	There are 100 or fewer airports.
1011,000	There are between 101 and 1,000 airports.
10011,0000	There are between 1,001 and 10,000 airports.
> 10,000	There are more than 10,000 airports.
No value in database	The number of airports is not available for this country.

Use a CASE statement to process your comparisons.

You can use the following code to get started:

DECLARE

v_country_name countries.country_name%TYPE := ''; v_airports countries.airports%TYPE;

BEGIN

SELECT airports INTO v_airports

FROM wf_countries

WHERE country_name = v_country_name;

CASE

WHEN ...

END CASE;

END;

Test your code for the following countries and confirm the results.

	No coastline	Small coastline	Mid-range coastline	Large coastline
Canada				X
Grenada		X
Jamaica			X
Japan				X
Mongolia	X
Ukraine			X

3.Use a CASE statement:

Write a PL/SQL block to select the number of countries using a supplied currency name. If the number of countries is greater than 20, display More than 20 countries. If the number of countries is between 10 and 20, display Between 10 and 20 countries. If the number of countries is less than 10, display Fewer than 10 countries. Use a CASE statement.

Test your code using the following data:

	Fewer than 10 countries	Between 10 and 20 countries	More than 20 countries
US Dollar		X
Swiss franc	X
Euro			X

4.Examine the following code.

What do you think the output will be? Test your prediction by running the code.

DECLARE x BOOLEAN := FALSE; y BOOLEAN;

v_color VARCHAR(20) := 'Red';

BEGIN

IF (x OR y)

THEN v_color := 'White'; ELSE

v_color := 'Black';

END IF;

DBMS_OUTPUT.PUT_LINE(v_color);

END;

Change the declarations to x and y as follows. What do you think the output will be? Test your prediction by running the code again.

xBOOLEAN ; y BOOLEAN ;

Change the declarations to x and y as follows. What do you think the output will be? Test your prediction by running the code again.

xBOOLEAN := TRUE; y BOOLEAN := TRUE;

Experiment with changing the OR condition to AND.