Update all SQL NULL values in multiple columns using Column level WHERE clause?

Question

We have a database with a bunch of wide tables (40-80 columns each) and just found a bug that introduced NULL values into about 500 of the records. The NULL values can appea

Answer 1

There isn't any convention to this -- if you want to only process records where respective columns are NULL, you need to use:

WHERE Answer_1 IS NULL 
   OR Answer_2 IS NULL 
   OR ...

But you could use this in the UPDATE statement:

UPDATE YOUR_TABLE
   SET col1 = COALESCE(col1, 99),
       col2 = COALESCE(col2, 99),
       col3 = ...

The logic is that the value will be updated to 99 only if the column value is NULL, because of how COALESCE works--returning the first non-NULL value (processing the list provided from left to right).