SQL COUNT function
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. Which query tells you how many records are in the Students table?
2. How many rows of output does SELECT COUNT(*) FROM Students; produce?
3. What does COUNT(*) do?
4. A table has 25 records. What does SELECT COUNT(*) FROM Students; output?
5. Which function would you use to find out HOW MANY students there are in a table?
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 1SELECT COUNT(*) FROM Students; | ASELECT COUNT(*) FROM Books; | |
| 2SELECT COUNT(StudentID) FROM Students WHERE Year = 10; | BThe FROM keyword is missing, so the SQL does not say which table to count the records in. | |
| 3To find how many records are in a table called Books, use COUNT rather than listing every record. | CSUM was used to count records. SUM adds up the values of a numeric field and cannot be used with *. COUNT(*) should be used. | |
| 4To add up the values in a numeric Price field instead of counting records, use SUM, not COUNT. | DOutputs one row containing the number of records in the Students table. | |
| 5SELECT COUNT(*) Students; | ECounts only the records where Year is 10 and outputs that total. | |
| 6SELECT SUM(*) FROM Students; | FSELECT SUM(Price) FROM Books; |
C
Definitions
COUNT(*)
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
SELECT _____(*) FROM Students;
2.
SELECT COUNT(_) FROM Students;
3.
SELECT COUNT(*) ____ Students;
4.
SELECT COUNT(*)
FROM Students
_____ Year = 9;
5.
SELECT ___(Points) FROM Students;
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
SELECT COUNT(*)
B
FROM Students
C
SELECT COUNT(*
Question 2
A
SELECT COUNT(StudentID)
B
FROM Students
C
WHERE Year == 9;
Question 3
A
SELECT SUM(*)
B
FROM Books
C
WHERE Price > 10;
Question 4
A
SELECT COUNT(*)
B
FROM Students
C
WHERE Year = 10
D
AND House = Blue;
Question 5
A
SELECT COUNT(*)
B
FORM Students
C
WHERE Points >= 100;
Answer Key
SQL COUNT function
Section A: Quick Questions
Q1
A — SELECT COUNT(*) FROM Students;
Q2
A — One row containing a single number
Q3
B — Counts the number of records
Q4
A — 25
Q5
B — COUNT
Section B: Match the Pairs
Q1
SELECT COUNT(*) FROM Students; → Outputs one row containing the number of records in the Students table.
Q2
SELECT COUNT(StudentID) FROM Students WHERE Year = 10; → Counts only the records where Year is 10 and outputs that total.
Q3
To find how many records are in a table called Books, use COUNT rather than listing every record. → SELECT COUNT(*) FROM Books;
Q4
To add up the values in a numeric Price field instead of counting records, use SUM, not COUNT. → SELECT SUM(Price) FROM Books;
Q5
SELECT COUNT(*) Students; → The FROM keyword is missing, so the SQL does not say which table to count the records in.
Q6
SELECT SUM(*) FROM Students; → SUM was used to count records. SUM adds up the values of a numeric field and cannot be used with *. COUNT(*) should be used.
Section C: Definitions
Q1
COUNT(*) — SQL function that counts records. SELECT COUNT(*) FROM Students; outputs one row with the number of records in the table. It counts rows, whereas SUM adds up values.Section D: Fill in the Blanks
Q1
SELECT COUNT(*) FROM Students;Q2
SELECT COUNT(*) FROM Students;Q3
SELECT COUNT(*) FROM Students;Q4
SELECT COUNT(*)
FROM Students
WHERE Year = 9;Q5
SELECT SUM(Points) FROM Students;Section E: Spot the Error
Q1
C — The closing bracket is missing from the COUNT function. It should be SELECT COUNT(*).
Q2
C — SQL uses a single = to compare values in a WHERE condition, not ==. It should be WHERE Year = 9;
Q3
A — SUM adds up the values in a numeric field, so it cannot be used with *. To count how many records match, use SELECT COUNT(*).
Q4
D — Text values in a WHERE condition must be inside quotes. It should be AND House = 'Blue';
Q5
B — The keyword is misspelt. It should be FROM, which names the table being counted.