Background
I want to rename my case statement in sql select statement dynamically.
Eg:
SELECT (case when id= x.id then x.sums
Below is for BigQuery!
Please note: your expectations about output column names are not correct!
Column name cannot start with digit - so in below example - i will be using id_1, id_2 and id_3 instead of 1, 2 and 3
SELECT
SUM(CASE WHEN id = 1 THEN 1 END) AS id_1,
SUM(CASE WHEN id = 2 THEN 1 END) AS id_2,
SUM(CASE WHEN id = 3 THEN 1 END) AS id_3
FROM YourTable
Above example assumes you know in advance your IDs and there are very few of them so it is not a big deal to write manually few numbers of lines with SUM(...) for each id
If this is not a case - you can first generate above query programmatically by running below query
SELECT 'SELECT ' +
GROUP_CONCAT_UNQUOTED(
'SUM(CASE WHEN id = ' + STRING(id) + ' THEN 1 END) AS id_' + STRING(id)
)
+ ' FROM YourTable'
FROM (
SELECT id FROM (
SELECT * FROM YourTable GROUP BY id ORDER BY id
)
as a result - you will get string like below
SELECT SUM(CASE WHEN id = 1 THEN 1 END) AS id_1,SUM(CASE WHEN id = 2 THEN 1 END) AS id_2,SUM(CASE WHEN id = 3 THEN 1 END) AS id_3 FROM YourTable
So, now just copy it and paste into Query Editor and run it
you can see similar example here - https://stackoverflow.com/a/36623258/5221944