Where is the syntax error in this WITH clause? - mysql

Question

I'm trying out this problem on LeetCode. The interface is throwing a syntax error, but for the life of me I can't figure it out. Here's the question:
Table: Stadium
+---------------+---------+
| Column Name | Type |
+---------------+---------+
| id | int |
| visit_date | date |
| people | int |
+---------------+---------+
visit_date is the primary key for this table. Each row of this table
contains the visit date and visit id to the stadium with the number of
people during the visit. No two rows will have the same visit_date,
and as the id increases, the dates increase as well.
Write an SQL query to display the records with three or more rows with
consecutive id's, and the number of people is greater than or equal to
100 for each.
Return the result table ordered by visit_date in ascending order.
The query result format is in the following example.
Stadium table:
+------+------------+-----------+
| id | visit_date | people |
+------+------------+-----------+
| 1 | 2017-01-01 | 10 |
| 2 | 2017-01-02 | 109 |
| 3 | 2017-01-03 | 150 |
| 4 | 2017-01-04 | 99 |
| 5 | 2017-01-05 | 145 |
| 6 | 2017-01-06 | 1455 |
| 7 | 2017-01-07 | 199 |
| 8 | 2017-01-09 | 188 |
+------+------------+-----------+
Result table:
+------+------------+-----------+
| id | visit_date | people |
+------+------------+-----------+
| 5 | 2017-01-05 | 145 |
| 6 | 2017-01-06 | 1455 |
| 7 | 2017-01-07 | 199 |
| 8 | 2017-01-09 | 188 |
+------+------------+-----------+
The four rows with ids 5, 6, 7, and 8 have consecutive ids and each of
them has >= 100 people attended. Note that row 8 was included even
though the visit_date was not the next day after row 7. The rows with
ids 2 and 3 are not included because we need at least three
consecutive ids.
Here's a fiddle with the data (NOTE: I'm still trying to figure out how to insert dates, so I saved the dates as strings instead).
Can anyone spot the syntax error in the query below?
# Write your MySQL query statement below
SET #rowIndex := 0;
WITH s1 as (
SELECT #rowIndex := #rowIndex + 1 as rowIndex, s.*
FROM Stadium as s
WHERE s.people >= 100
GROUP BY s.id
)
SELECT s2.id, s2.visit_date, s2.people
FROM s1 as s2
GROUP BY s2.rowIndex - s2.id, s2.id, s2.visit_date, s2.people
ORDER BY s2.visit_date
Error message:
You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use
near 'WITH s1 (rowIndex, id, visit_date, people) as (
SELECT #rowIndex := #rowInde' at line 4
Also, the LeetCode interface uses MySQL v8.0, so I don't think that's the problem.
I was using the query below as a reference. (Original.)
SET #rowIndex := -1;
SELECT ROUND(AVG(t.LAT_N), 4) FROM
(
SELECT #rowIndex := #rowIndex+1 AS rowIndex, s.LAT_N FROM STATION AS s ORDER BY s.LAT_N
) AS t
WHERE t.rowIndex IN (FLOOR(#rowIndex / 2), CEIL(#rowIndex / 2));
Thanks.
Edit:
For future reference, here's the final query I came up with:
# Write your MySQL query statement below
WITH s1 as (
SELECT ROW_NUMBER() OVER (ORDER BY s.id) as rowIndex, s.*
FROM Stadium as s
WHERE s.people >= 100
GROUP BY s.id, s.visit_date, s.people
), s2 as (
SELECT COUNT(s.id) OVER (PARTITION BY s.id-s.rowIndex) as groupSize, s.*
FROM s1 as s
)
SELECT s3.id, s3.visit_date, s3.people
FROM s2 as s3
GROUP BY s3.groupSize, s3.id, s3.visit_date, s3.people
HAVING s3.groupSize >= 3
ORDER BY s3.visit_date

Answer 1

You confirmed that you are using MySQL 8.0.21 server so the only other suggestion I have is that you're trying to run two SQL statements in one call:
SET #rowIndex := 0;
WITH s1 as (
SELECT...
Most MySQL connectors do not support multi-query by default. In other words, you can only do one statement per call. As soon as MySQL sees any syntax following your first ; it treats this as a syntax error.
There's no reason you need to use multi-query. Just run the two statements separately. As long as you use the same session, your value of #rowIndex will be available to subsequent statements.
The former Director of Engineering for MySQL once told me, "there's no reason multi-query should exist."

Answer 2

Not sure what problem you might be facing, yet this would pass on LeetCode:
Not sure if that's a right way to do it:
SELECT DISTINCT S1.id,
S1.visit_date,
S1.people
FROM stadium AS S1,
stadium AS S2,
stadium AS S3
WHERE S1.people > 99
AND S2.people > 99
AND S3.people > 99
AND ( (S2.id = S1.id + 1
AND S3.id = S1.id + 2)
OR (S2.id = S1.id - 1
AND S3.id = S1.id + 1)
OR (S2.id = S1.id - 1
AND S3.id = S1.id - 2) )
ORDER BY id ASC;