Tag: databases

Questions Related to databases

  1. NULL

  2. 0

  3. Results in a compilation error

  4. An exception will be raised


Correct Option: A
Explanation:

The answer to the question is A. NULL.

When a variable is declared in PL/SQL without an initial value, it is initialized to NULL. This means that the variable has no value, and any attempt to use it will result in a NULL value.

Option B is incorrect because the value of a NUMBER variable is not automatically initialized to 0. Option C is incorrect because a compilation error will not occur if a variable is declared without an initial value. Option D is incorrect because an exception will not be raised if a variable is declared without an initial value.

Here is an example of how a NULL value is handled in PL/SQL:

DECLARE
  v_number NUMBER;
BEGIN
  v_number := NULL;
  dbms_output.put_line(v_number); -- This will print 'NULL'
END;

As you can see, the value of v_number is printed as NULL when it is first used in the executable section of the PL/SQL block. This is because the variable was declared without an initial value, and therefore its value is NULL.

  1. SELECT name FROM USER_DEPENDENCIES WHERE referenced_name = 'DBMS_OUTPUT.PUT_LINE'

  2. SELECT name from ALL_SOURCE WHERE owner = USER AND name = 'DBMS_OUTPUT.PUT_LINE'

  3. SELECT DISTINCT name from ALL_SOURCE WHERE INSTR (text, 'DBMS_OUTPUT.PUT_LINE') > 0

  4. SELECT DISTINCT name from USER_SOURCE WHERE INSTR (UPPER (text), 'DBMS_OUTPUT.PUT_LINE') > 0


Correct Option: D
  1. When a SELECT statement returns no rows

  2. When a SELECT statement returns more than one row

  3. When the datatypes of SELECT clause and INTO clause do not match

  4. When INTO statement is missing in the SELECT statement


Correct Option: A,B
  1. Begin null; end;

  2. Declare x varchar2(100); begin dbms_output.put_line(x); end;

  3. Begin .. statement1; exception ... end;

  4. Begin dbms_output.put_line(sysdate); end;;


Correct Option: A

Maximum no of columns in a key.

  1. 1

  2. 31

  3. 16

  4. 255


Correct Option: B