如何使用 SQL 在表中创建一个新列以仅显示来自另一列的特定数据？

Question

I am trying to figure out how to create a new column in a table that will be labelled as Release_Year and that will only show the year that each movie was released.

Example

I have not attempted to run a query as I do not know where to begin.

Answer 1

You need to add a new column of type int.

ALTER TABLE `projectID.datasetID.movie_table`
ADD COLUMN Release_Year int64;

Then you need to fill the column with values, you can do this using a merge statement. We also use a group by to ensure we have unique mappings.

merge into `projectID.datasetID.movie_table` as target_table
using (
select
movie_title,
extract(year from release_date) as release_year
from
`projectID.datasetID.movie_table`
group by
movie_title,
release_year) as mapping
on
mapping.movie_title = target_table.movie_title
when matched
then
update set target_table.release_year = mapping.release_year

This is untested but the general idea should work.