Which two statements are true regarding the COUNT function?

Which two statements are true regarding the COUNT function? (Choose two.)

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.



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Innez

Innez

WHy option C is wrong ?

Striker

Striker

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.

Justyna

Justyna

count(cust_id) does not return rows with NULL values in the column CUST_ID