Differences between row in google big query - sql

Question

I'm currently attempting to calculate differences between rows in google big query. I actually have a working query.
SELECT
id, record_time, level, lag,
(level - lag) as diff
FROM (
SELECT
id, record_time, level,
LAG(level) OVER (ORDER BY id, record_time) as lag
FROM (
SELECT
*
FROM
TABLE_QUERY(MY_TABLES))
ORDER BY
1, 2 ASC
)
GROUP BY 1, 2, 3, 4
ORDER BY 1, 2 ASC
But I'm working with big data and sometimes I have memory limit warning that does not let me execute the query. So, I would like to understand why I cant do an optimized query like bellow. I think it will allow work with more records without memory limit warning.
SELECT
id, record_time, level,
level - LAG(level, 1) OVER (ORDER BY id, record_time) as diff
FROM (
SELECT
*
FROM
TABLE_QUERY(MY_TABLES))
ORDER BY
1, 2 ASC
This kind of function level - LAG(level, 1) OVER (ORDER BY id, record_time) as diff, when the query is executed returns the error
Missing function in Analytic Expression
on Big Query.
I also tried to put ( ) into this function but it does not work as well.
Thanks for helping me!

Answer 1

It works fine for me. Maybe you forgot to enable standard SQL? Here is an example:
WITH Input AS (
SELECT 1 AS id, TIMESTAMP '2017-10-17 00:00:00' AS record_time, 2 AS level UNION ALL
SELECT 2, TIMESTAMP '2017-10-16 00:00:00', 3 UNION ALL
SELECT 1, TIMESTAMP '2017-10-16 00:00:00', 4
)
SELECT
id, record_time, level, lag,
(level - lag) as diff
FROM (
SELECT
id, record_time, level,
LAG(level) OVER (ORDER BY id, record_time) as lag
FROM Input
)
GROUP BY 1, 2, 3, 4
ORDER BY 1, 2 ASC;