sql - Does the number of columns updated affect the performance of update query in Oracle -


i have oracle update query below

query1 : update table1 set col1=value1 tablekey=123

query2 : update table1 set col1=value1,col2=value2 tablekey=123

will there performance difference between these two?

nothing much, except number of bytes.

you check explain plan:

sql> explain plan update emp set ename='a' empno=7369;  explained.  sql> sql> select * table(dbms_xplan.display);  plan_table_output -------------------------------------------------------------------------------- plan hash value: 1494045816  --------------------------------------------------------------------------- | id  | operation          | name | rows  | bytes | cost (%cpu)| time     | --------------------------------------------------------------------------- |   0 | update statement   |      |     1 |    10 |     3   (0)| 00:00:01 | |   1 |  update            | emp  |       |       |            |          | |*  2 |   table access full| emp  |     1 |    10 |     3   (0)| 00:00:01 | ---------------------------------------------------------------------------  predicate information (identified operation id):  plan_table_output -------------------------------------------------------------------------------- ---------------------------------------------------     2 - filter("empno"=7369)  14 rows selected.  sql> sql> explain plan update emp set ename='a', deptno=30 empno=7369;  explained.  sql> sql> select * table(dbms_xplan.display);  plan_table_output -------------------------------------------------------------------------------- plan hash value: 1494045816  --------------------------------------------------------------------------- | id  | operation          | name | rows  | bytes | cost (%cpu)| time     | --------------------------------------------------------------------------- |   0 | update statement   |      |     1 |    13 |     3   (0)| 00:00:01 | |   1 |  update            | emp  |       |       |            |          | |*  2 |   table access full| emp  |     1 |    13 |     3   (0)| 00:00:01 | ---------------------------------------------------------------------------  predicate information (identified operation id):  plan_table_output -------------------------------------------------------------------------------- ---------------------------------------------------     2 - filter("empno"=7369)  14 rows selected.

for more detailed information, set autotrace on:

sql> set autotrace on sql> update emp set ename='a' empno=7369;  1 row updated.   execution plan ---------------------------------------------------------- plan hash value: 1494045816  --------------------------------------------------------------------------- | id  | operation          | name | rows  | bytes | cost (%cpu)| time     | --------------------------------------------------------------------------- |   0 | update statement   |      |     1 |    10 |     3   (0)| 00:00:01 | |   1 |  update            | emp  |       |       |            |          | |*  2 |   table access full| emp  |     1 |    10 |     3   (0)| 00:00:01 | ---------------------------------------------------------------------------  predicate information (identified operation id): ---------------------------------------------------     2 - filter("empno"=7369)   statistics ----------------------------------------------------------           4  recursive calls           1  db block gets           3  consistent gets           0  physical reads         352  redo size         857  bytes sent via sql*net client         842  bytes received via sql*net client           3  sql*net roundtrips to/from client           2  sorts (memory)           0  sorts (disk)           1  rows processed  sql> update emp set ename='a', deptno=30 empno=7369;  1 row updated.   execution plan ---------------------------------------------------------- plan hash value: 1494045816  --------------------------------------------------------------------------- | id  | operation          | name | rows  | bytes | cost (%cpu)| time     | --------------------------------------------------------------------------- |   0 | update statement   |      |     1 |    13 |     3   (0)| 00:00:01 | |   1 |  update            | emp  |       |       |            |          | |*  2 |   table access full| emp  |     1 |    13 |     3   (0)| 00:00:01 | ---------------------------------------------------------------------------  predicate information (identified operation id): ---------------------------------------------------     2 - filter("empno"=7369)   statistics ----------------------------------------------------------           4  recursive calls           1  db block gets           3  consistent gets           0  physical reads         316  redo size         858  bytes sent via sql*net client         853  bytes received via sql*net client           3  sql*net roundtrips to/from client           2  sorts (memory)           0  sorts (disk)           1  rows processed  sql>

so, see slight difference bytes sent via sql*net client , bytes received via sql*net client. more columns, difference increase more.


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