Which two statements are true regarding the COUNT function? (Choose two.)
A.
The COUNT function can be used only for CHAR, VARCHAR2, and NUMBER data types.
B.
COUNT(*) returns the number of rows including duplicate rows and rows containing NULL value in
any of the columns.
C.
COUNT(cust_id) returns the number of rows including rows with duplicate customer IDs and NULL
value in the CUST_ID column.
D.
COUNT(DISTINCT inv_amt)returns the number of rows excluding rows containing duplicates and
NULL values in the INV_AMT column.
E.
A SELECT statement using the COUNT function with a DISTINCT keyword cannot have a WHERE clause.
Explanation:
Using the COUNT Function
The COUNT function has three formats:
COUNT(*)
COUNT(expr)
COUNT(DISTINCT expr)
COUNT(*) returns the number of rows in a table that satisfy the criteria of the SELECT statement,
including duplicate rows and rows containing null values in any of the columns. If a WHERE clause
is included in the SELECT statement, COUNT(*) returns the number of rows that satisfy the
condition in the WHERE clause.
In contrast,
COUNT(expr) returns the number of non-null values that are in the column identified by expr.
COUNT(DISTINCT expr) returns the number of unique, non-null values that are in the column
identified by expr.