Quiz 13
Question # 1
Which MySQL statement will delete a table from database and free space in memory while keeping the structure of the table intact?
A)
DELETE FROM TABLE table_name;
B)
DROP TABLE table_name;
C)
TRUNCATE TABLE table_name;
Question # 2
Consider the following queries which give the same result. Pick the most efficient.
A)
SELECT * FROM table_name WHERE col1 = x OR col2 = y;
B)
SELECT * FROM table_name WHERE col1 = x
UNION ALL
SELECT * FROM table_name WHERE col2 = y AND col1 != x;
C)
SELECT * FROM table_name WHERE col1 = x
UNION DISTINCT
SELECT * FROM table_name WHERE col2 = y;
Question # 3
Which MySQL function assigns a sequential number to each row of a table that starts with one?
A)
ROW_ID()
B)
ROW_NUM()
C)
ROW_NUMBER()
Question # 4
Suppose you perform an UPSERT i.e. a conditional update or insertion into a table. If a row exists, an UPDATE is done and if a row does not exist, an INSERT is performed. Which statement will you use?
A)
MERGE
B)
UPSERT
C)
INSERT with ON DUPLICATE KEY UPDATE
Question # 5
Which option is true for the following statement: The output of a sub-query is dependent on the column values of the parent query table.
A)
Nested sub-query
B)
Correlated sub-query
