What does COUNT(*) do in MySQL [duplicate]

Question

SELECT exam_board, COUNT(*)
FROM subjects
GROUP BY exam_board;

This is a block of code where 'exam_board' is a field in a table called 'subjects'.

What does each line of code in this block do?

Waldson Patricio · Accepted Answer · 2016-10-20 18:49:58Z

2

Gives you how much records have the same exam_board value for each different exam_board value.

For example, if your table has this data:

|exam_board|
 A
 A
 A
 B
 B

this query will return:

|exam_board |COUNT(*)
 A            3
 B            2

answered Oct 20, 2016 at 18:49

Waldson Patricio

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Comments

gschambial · Accepted Answer · 2016-10-20 18:45:34Z

0

Gives you the count of total number of records fetched in query.

In your specific case, it will give you count of each exam_board group.

exam_board  count
A           10
B           29

Something like this.

answered Oct 20, 2016 at 18:45

gschambial

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