Ниже для BigQuery Standard SQL
#standardSQL
WITH `project.dataset.table` AS (
SELECT '100/1802/5' Qualification_No, 10 col_2019_2, 20 col_2019_1, 30 col_2018_4 UNION ALL
SELECT '100/1811/6', 15, 23, 10
)
SELECT Qualification_No, No_of_certification
FROM `project.dataset.table`,
UNNEST([col_2019_2, col_2019_1, col_2018_4]) No_of_certification
с результатом
Row Qualification_No No_of_certification
1 100/1802/5 10
2 100/1802/5 20
3 100/1802/5 30
4 100/1811/6 15
5 100/1811/6 23
6 100/1811/6 10