How to overwrite column values in bigquery existing table

Question

I need to overwrite/update column values in bigquery. The problem with solution bellow is it loads lots of data every time need to upload few records. Need a more optimal solution which will only upload the id's that matches.

Extra: it would be even better if it could check if the value is the same, if not it doesn't update the record. I would think it would reduce even more with load

table 1:

name   id    value
jose   1     10
jack   5     15
lex    4   12

table 2:

id   value
1    200
2    200
3    700
4    800
5    200

Query:

select
t1.name,
t1.id,
t2.value

from table 1 as t1
left join table2 as t2
on t1.id=t2.id

The example in the link bellow creates a new table, so doesn't work. It need to update values in the existing table.

changing column values in bigquery

Answer 1

You got this wrong.

In BigQuery you pay what you read and not what you write. So if you need to read a lot of rows to compare, for every read you pay, and the write is free. So you should reduce with a WHERE logic the number of items you "read" to reduce your costs.