CASE Statements and expressions

Question 1

The Oracle/PLSQL CASE statement has the functionality of an ____

Answer 1

IF-THEN-ELSE statement

Question 2

What types of datatypes can a case statement return?

Answer 2

Any type

Question 3

Can different cases in a case statement return different datatypes?

Answer 3

No, all results must be the same datatype

Question 4

What will the case statment return if all of the conditions are false and there is no else clause?

Answer 4

NULL

Question 5

What are the 2 types of case statements?

Answer 5

• Simple CASE statement

- Searched CASE statement

Question 6

What does a simple CASE statement do?

Answer 6

Evaluates a single expression

Compares the result with some values

Question 7

What is the syntax for a simple CASE statement?

Answer 7

CASE selector
WHEN selector_value_1 THEN
    statements_1
WHEN selector_value_1 THEN 
    statement_2
...
ELSE
    else_statements
END CASE;

Question 8

PL/SQL will implicitly use if you do not provide an else clause?

Answer 8

ELSE

RAISE CASE_NOT_FOUND;

Question 9

What does a searched CASE statement do?

Answer 9

Evaluates multiple Boolean expressions

Executes the sequence of statements associated with the first condition that evaluates to TRUE

Question 10

What is the syntax for a searched CASE statement?

Answer 10

CASE
WHEN condition_1 THEN statements_1
WHEN condition_2 THEN statements_2
...
WHEN condition_n THEN statements_n
[ ELSE
  else_statements ]
END CASE;]

Question 11

In a searched CASE statement what order are the conditions in the WHEN clauses evaluated?

Answer 11

Top to bottom

Question 12

In a searched CASE statement which condition fires if there are multiple WHEN clause whose condition evaluates to true?

Answer 12

The first one

Question 13

What is a CASE expression?

Answer 13

A CASE expression evaluates a list of conditions and returns one of multiple possible result expressions