2

I have a query that looks like below:

UPDATE some_table
SET column_x = CASE WHEN x_specific_condition THEN new_value_for_x ELSE column_x END,
    column_y = CASE WHEN y_specific_condition THEN new_value_for_y ELSE column_y END, 
WHERE some_more_conditions

Problem with above is, each column (x, y) still gets updated with their own value if some_more_conditions return true irrespective of their specific conditions returning true. I tried removing ELSE from above, but no luck

I am combining as some_more_conditions are same for both cases, I think its better to perform all in 1 update (suggestions welcome)

Do you know if there is a way that can I can perform the above update in 1 query by skipping the individual columns where the specific conditions do not match (basically avoid overwriting of same values)

  • 2
    If you specify a column should be updated then it will always be updated(Either with new value according to the condition or with original value). – JSapkota Mar 18 '16 at 4:39
3

Both columns specified in the SET clause of your UPDATE are going to be touched (written to) for all the rows matching the some_more_conditions, no matter what x_specific_condition or y_specific_condition may evaluate to. There is no syntax to work around that while sticking to a single statement.

So, either live with that or go for two statements:

UPDATE some_table
SET column_x = new_value_for_x
WHERE some_more_conditions
  AND x_specific_condition;

UPDATE some_table
SET column_y = new_value_for_y
WHERE some_more_conditions
  AND y_specific_condition;

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