Welcome to Stackoverflow. Can you provide the query you tried and the error message you get.

I assume your are trying to update the values from NULL to 0 in one or more columns in one or more tables.

First of all does the datatype of the column allow 0 as valid input?

• INT64, FLOAT64, and NUMERIC are examples of datatypes which allows 0.

• Where STRING doesn’t allow 0, but do allow ‘0’.

You can update all columns at once. But I would recomend to only update one column at a time and repeat the proces untill all desired columns are updated. In that way you will also figure out if your whole approach is wrong or there only is a problem with a few columns and faster find the rootcause of the issues.

UPDATE your_table
SET your_column = 0
WHERE your_column IS NULL

To avoid doing the above from time to time, you can consider changing the default value to be 0 instead for each relevant column, then you would never have to deal with NULL in those again:

ALTER TABLE your_table
ALTER COLUMN your_column SET DEFAULT 0;