Select an SQL value from column where separate column is MIN()

Question

I am developing an assignment function for orders and I am trying to assign the order to a user who has the least pending requests. I want to get the user id where the value for pending is the least of all of the users.

Example:

userID    pending
------    -------
0         3
1         0 <----This user has the least pending of all
2         4

How do I set up an SQL Query to return the user ID with the least amount of pending request of the table?

$sql="SELECT user_id FROM writerdata_tb WHERE pending = '//Minimum pending here//' LIMIT 1";
$assign = $conn->query($sql);
$row = $assign->fetch_assoc();

Answer 1

A comparison of various possible answers proposed:

EXPLAIN SELECT aa.userId, aa.pending
FROM writerdata_tb AS aa
INNER JOIN writerdata_tb AS bb 
ON aa.userId = bb.userId
WHERE aa.pending >= bb.pending
ORDER BY aa.pending ASC
LIMIT 1;

id  select_type     table   type    possible_keys   key     key_len     ref     rows    Extra   
1   SIMPLE  aa  ALL     PRIMARY     NULL    NULL    NULL    4   Using temporary; Using filesort
1   SIMPLE  bb  ALL     PRIMARY     NULL    NULL    NULL    4   Using where; Using join buffer (Block Nested Loop)

---

EXPLAIN SELECT userId, pending
FROM writerdata_tb
WHERE pending = (
    SELECT MIN(pending)
    FROM writerdata_tb 
);

id  select_type     table   type    possible_keys   key     key_len     ref     rows    Extra   
1   PRIMARY     writerdata_tb   ALL     NULL    NULL    NULL    NULL    4   Using where
2   SUBQUERY    writerdata_tb   ALL     NULL    NULL    NULL    NULL    4   NULL

---

EXPLAIN SELECT userId, pending
FROM writerdata_tb
ORDER BY pending ASC
LIMIT 1;

id  select_type     table   type    possible_keys   key     key_len     ref     rows    Extra   
1   SIMPLE  writerdata_tb   ALL     NULL    NULL    NULL    NULL    4   Using filesort

---

EXPLAIN SELECT t.userId
FROM writerdata_tb AS t
GROUP BY (
    t.userId
)
ORDER BY SUM(pending) ASC
LIMIT 1;

id  select_type     table   type    possible_keys   key     key_len     ref     rows    Extra   
1   SIMPLE  t   index   PRIMARY     PRIMARY     4   NULL    4   Using temporary; Using filesort

Answer 2

You can order results by column pending (see comment by Simone Nigro for the query). Using the limit word, in the result you will get only the first row, in this case you will get the result with minium pending value.

I see now the case of Aleksandar Miladinovic, if in the table there are many rows with same value of pending : you can execute:

1. A query to get the mininium value of pending column

2. Use the value obtained in the previous step to receive the rows with that value

   SELECT user_id FROM writerdata_tb WHERE pending=(SELECT min(pending) FROM writerdata_tb)

Answer 3

尝试这种方式：从writerdata_tb中选择userID，其中未决=（从writerdata_tb中选择min（pending））；

Answer 4

If UserID's are repeated

SELECT
    t.userID
from 
    tasks as t
group by (t.userID)
order by sum(pending) asc 
limit 1

else

SELECT
    t.userID
from 
    tasks as t
order by pending asc 
limit 1