如何将函数的结果存储到变量中？

Question

Please take a look at it:

SELECT calculate_both_score_and_reputation(u.id) AS sr FROM users u

It returns something like this:

+----------+
|    sr    |
+----------+
| 0,1322   |
| 3, 232   |
| -2, 9978 |
| 31, 5745 |
+----------+

---

Now I want to split the result of that function into two different columns:

SELECT SUBSTRING_INDEX(calculate_both_score_and_reputation(u.id),',', 1) AS s,
       SUBSTRING_INDEX(calculate_both_score_and_reputation(u.id),',', -1) AS r,
FROM users u

Here is the result:

+----+------+
| s  |   r  |
+----+------+
| 0  | 1322 |
| 3  | 232  |
| -2 | 9978 |
| 31 | 5745 |
+----+------+

---

The result is as expected. But as you see, that function will be called twice. Now I want to know, how can I call that function once and store the result in a variable, then parse that variable?

Answer 1

You can simply place your query in a subquery and consume the value returned by the function in the outer query:

SELECT SUBSTRING_INDEX(sr,',', 1) AS s,
       SUBSTRING_INDEX(sr,',', -1) AS r
FROM (
 SELECT calculate_both_score_and_reputation(u.id) AS sr 
 FROM users u) AS t