Question

Question 1

Can anyone tell me if there is any difference between following 2 update statements:

UPDATE TABA SET COL1 = '123', COL2 = '456' WHERE TABA.PK = 1
UPDATE TABA SET COL1 = '123' WHERE TABA.PK = 1

where the original value of COL2 = ‘456’

how does this affect the UNDO?

Question 2
What about if I update a record in table TABA using ROWTYPE like the following snippet.
how’s the performance, and how does it affect the UNDO?

SampleRT TABA%rowtype

SELECT * INTO SampleRT FROM TABA WHERE PK = 1;
SampleRT.COL2 = '111';
UPDATE TABA SET ROW = SampleRT WHERE PK = SampleRT.PK;

thanks

Answer 1

Is your question 1 asking whether UNDO (and REDO) is generated when you’re running an UPDATE against a row but not actually changing the value?

Something like?

update taba set col2='456' where col2='456';

If this is the question, then the answer is that even if you’re updating a column to the same value then UNDO (and REDO) is generated.

(An exception is when you’re updating a NULL column to NULL – this doesn’t generate any REDO).