select name and email and count using subquery in postgresql

Question

I'm trying write a Postgres query to display a distinct number of people but count the actual (non-distinct) number of people.

So if I have

1  Ray ray@gmail.com
2  Ray ray@gmail.com
3  Kate kate@gmail.com

I'd want to show:

Ray 2
Kate 1

==

SELECT name, email, COUNT(*) 
FROM (SELECT DISTINCT name, email 
FROM people
WHERE degree = 'Gradiate') 

I get:

ERROR:  subquery in FROM must have an alias
LINE 3: FROM (SELECT DISTINCT name, email

How to fix this?

Answer 1

You do not need the subquery at all (which would require a table alias as has been pointed out). It wouldn't make sense for what you need.

Use GROUP BY like this:

SELECT name, email, count(*) AS ct
FROM   people
WHERE  degree = 'Graduate'
GROUP  BY 1, 2;

GROUP BY 1, 2 is shorthand for GROUP BY name, email in this case. Example with more details.

Of course, name and email have to match here, unlike your example where you only display name and count (which contradicts your query).

Answer 2

Add an

AS some_alias

Like:

SELECT name, email, COUNT(*) 
FROM (SELECT DISTINCT name, email 
FROM people
WHERE degree = 'Gradiate') as my_alias

Answer 3

SELECT name, count(*) AS count
FROM   people
WHERE  degree = 'Gradiate'
GROUP  BY name;