Select Distinct between two tables inner join - mysql

Question

I have table 1 which contains unique values and table 2 which contains multiple values for the same email. What I want to do is select the first value of 'id' - table 2 contains a number of ids and matching emails
SELECT DISTINCT
table1.email,
table2.id FROM
table1
INNER JOIN users ON table1.email = table2.Email
the problem is the output needs to be unique - i.e. one ID - the first one from table2 that is associated with a given email - currently we're getting multiple results - no unique or distinct values.

Answer 1

Probably
any id - add ORDER BY RAND()
1 row of result - add LIMIT 1.
So, the query might be something like this:
SELECT DISTINCT
table1.email,
table2.id
FROM table1
INNER JOIN table2 ON table1.email = table2.email
ORDER BY RAND()
LIMIT 1
Based on new information, it seems like you're looking for something like this instead:
Note: Works on MySQL v8+ and MariaDB 10.2+ that have window function:
SELECT email, id
FROM
(SELECT table1.email,
table2.id,
ROW_NUMBER()
OVER
(PARTITION BY table1.email ORDER BY table2.id) AS 'RowNumber'
FROM table1
INNER JOIN table2 ON table1.email = table2.email) t
WHERE RowNumber=1;
Assign ROW_NUMBER() with table1.email as partition and sort by table2.id ascending (note that the default sorting of ORDER BY is ascending so there's no need to define it as ORDER BY xxx ASC).
Turn the base query into a subquery then do a SELECT .. with condition of WHERE RowNumber=1. Hence, it will return only a single row for each email.
Alternatively, depending on your data, you could just simply do something like this:
SELECT table1.email,
MIN(table2.id) AS minID
FROM table1
INNER JOIN table2 ON table1.email = table2.email
GROUP BY table1.email;
Demo fiddle