Getting Distinct Value Counts Across Multiple Fields/Tables in One MySQL Query - mysql

Question

I have a table called visits which contains the following
link_id, id, browser, country, referer
Now, this basically records visits of a certain link and inserts the browser, country and referer of whomever visted that link in a database
Now I need to show statistics for each link
I used the following query to get me all the browsers
SELECT browser, COUNT(browser) FROM visits GROUP BY browser
Which produced something like
Browser Count(Browser)
Internet Explorer | 5
Chrome | 3
Now this worked as expected for browsers only but I'm looking for a way to count all occurrences of referers, browsers and countries in one single query.
Is there a way to do this?

Answer 1

To count multiple, different occurence counts of values in the DB can very easily be done in just one query.
Keep in mind, the column header in SELECT COUNT(tablename) returns only one column, with only one numeric value. For every distinct value (from the GROUP BY clause), you have two columns: Value, Count. To count for different fields, you'll need three: Field, Value, Count, and if you want to count different fields in different tables, you'll need four: Table, Field, Value, Count.
Observe how I am using UNION below for two different tables:
SELECT
"Table1" AS TableName,
"Field1" AS Field,
Field1 AS Value,
COUNT(Field1) AS COUNT
FROM Table1
GROUP BY Value
UNION
SELECT
"Table2" as TableName,
"Field2" as Field,
Field2 as Value,
COUNT(Field2) AS COUNT
FROM Table2
GROUP BY Value
You'll notice I need to use aliases: "Table2" as TableName, this is because the UNION'd columns ought to have matching column headers.
So you can visualize what this returns, take a look:
+-------------------+----------------+----------+--------+
| TableName | Field | Value | COUNT |
+-------------------+----------------+----------+--------+
| ItemFee | PaymentType | | 228 |
| ItemFee | PaymentType | All | 1 |
| ItemFee | PaymentType | PaidOnly | 1 |
| Person | Presenter | | 692258 |
| Person | Presenter | N | 590 |
| Person | Presenter | Y | 8103 |
+-------------------+----------------+----------+--------+