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Suppose a table like this:
CREATE TABLE TABLE_A
(COL_1 INT NOT NULL PRIMARY KEY,
COL_2 CHAR(1) NOT NULL);
and a SQL statement like this:
UPDATE TABLE_A SET COL_1 = ? AND COL_2 =? WHERE COL_1 = ?;
The SQL is prepared using Type 4 Java driver and executed.
If the value of COL_1 is always the same as the existing value, but COL_2 is
always different than the existing value, does DB2 actually update/log the
update of COL_1 and the update the index on column COL_1 even though the
value has not changed?
In other words, the SQL should look like this:
UPDATE TABLE_A SET COL_2 =? WHERE COL_1 = ?;
This is a very high volume SQL statement in an application and I am trying
to assess how much extra work is being done by DB2 that should not be done
if the SQL was coded properly (because the COL_1 value never actually
changes).
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