SQL - Update a table using LAG and based on another column - sql

Question

I have a dashboard with python and dash/plotly that receives inputs from the user and then run a query on Google BigQuery.
One of the queries updates a column (PAY_FT), uses other column (PAY_CLEAN) and a string input from the dashboard.
DECLARE cpi STRING DEFAULT "C";
UPDATE `xx.yy.zz` t
SET
PAY_FT = s.PAY_FT
FROM
(
SELECT
RN,
CASE
WHEN RN = 1 AND cpi = "S" AND PAY_SHALE_COR = "PAY" THEN 1
WHEN RN = 1 AND cpi = "C" AND PAY_CLEAN = "PAY" THEN 1
WHEN RN = 1 THEN 0
WHEN RN > 1 AND cpi = "S" AND PAY_SHALE_COR = "PAY" THEN 0.2 + (LAG(PAY_FT, 1) OVER(ORDER BY RN))
WHEN RN > 1 AND cpi = "C" AND PAY_CLEAN = "PAY" THEN 0.2 + (LAG(PAY_FT, 1) OVER(ORDER BY RN))
ELSE (LAG(PAY_FT, 1) OVER(ORDER BY RN))
END
AS PAY_FT
FROM
`xx.yy.zz`
WHERE
DEPTH_M IS NOT NULL
)
s
WHERE
t.RN = s.RN
But it's not working as intended. This query returns the following:
It works until DEPTH_M = 102.2, but after that it dows not return the 0.4 from the previous row. So, for example, if we had a "PAY" in DEPTH_M = 103.2, until 103.0 should return 0.4 and in 103.2 it should be 0.6.
How can I fix it?
Here's a sample of my data: SAMPLE.csv
My desired outpu should be:
DEPTH_M
PAY_CLEAN
PAY_FT
101.2
PAY
0.2
101.4
PAY
0.4
101.6
-
0.4
101.8
-
0.4
102.0
-
0.4
102.2
-
0.4
102.4
-
0.4
102.6
-
0.4
102.8
-
0.4
103.0
-
0.4
103.2
-
0.4
103.4
-
0.4
Let's say that we got another PAY on another row, the output should be:
DEPTH_M
PAY_CLEAN
PAY_FT
101.2
PAY
0.2
101.4
PAY
0.4
101.6
-
0.4
101.8
-
0.4
102.0
-
0.4
102.2
-
0.4
102.4
-
0.4
102.6
-
0.4
102.8
-
0.4
103.0
PAY
0.6
103.2
-
0.6
103.4
-
0.6
Thanks in advance.

Answer 1

on the second thought you can go with this query which is much simpler and does what you want and you don't need to check for RN :
SELECT RN
,0.2 * COUNT(CASE WHEN (cpi = "S" AND PAY_SHALE_COR = "PAY")
OR (cpi = "C" AND PAY_CLEAN = "PAY") THEN 1 END) OVER (ORDER BY RN)
+ SUM(CASE WHEN RN = 1 AND ((cpi = "S" AND PAY_SHALE_COR = "PAY")
OR (cpi = "C" AND PAY_CLEAN = "PAY")) THEN 0.8 ELSE 0 end) OVER () NEW_Pay_FT
FROM `xx.yy.zz`
WHERE DEPTH_M IS NOT NULL