Don't update column if update value is null

Question

I have a query like this (in a function):

UPDATE some_table SET
  column_1 = param_1,
  column_2 = param_2,
  column_3 = param_3,
  column_4 = param_4,
  column_         


        

Answer 1

Additionally, to avoid empty updates:

UPDATE some_table SET
  column_1 = COALESCE(param_1, column_1),
  column_2 = COALESCE(param_2, column_2)
  ...
WHERE id = some_id;
AND  (param_1 IS DISTINCT FROM column_1 OR
      param_2 IS DISTINCT FROM column_2 OR
      ...
     );

This assumes target columns to be defined NOT NULL. Else, see Geir's extended version.

Answer 2

Neat trick, thanks Przemek, Frank & Erwin!

I suggest a minor edit to Erwin's answer to avoid empty updates. If any parameters were null (meaning: "use the old value"), the row was updated each time even though the row values did not change (after the first update).

By adding "param_x IS NOT NULL", we avoid empty updates:

UPDATE some_table SET
    column_1 = COALESCE(param_1, column_1),
    column_2 = COALESCE(param_2, column_2),
    ...
WHERE id = some_id
AND  (param_1 IS NOT NULL AND param_1 IS DISTINCT FROM column_1 OR
      param_2 IS NOT NULL AND param_2 IS DISTINCT FROM column_2 OR
     ...
 );

Answer 3

Drop the SELECT statement, there is no need for, just use the current value:

UPDATE some_table SET
  column_1 = COALESCE(param_1, column_1),
  column_2 = COALESCE(param_2, column_2),
  column_3 = COALESCE(param_3, column_3),
  column_4 = COALESCE(param_4, column_4),
  column_5 = COALESCE(param_5, column_5)
WHERE id = some_id;