更新时间:2022-09-01 11:19:31
alter table t add (x1 number default NULL);
alter table t add (x2 number default NULL );
SQL> select * from v$version ;
BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bi
PL/SQL Release 10.2.0.4.0 - Production
CORE 10.2.0.4.0 Production
TNS for Linux: Version 10.2.0.4.0 - Production
NLSRTL Version 10.2.0.4.0 - Production
drop table t purge ;
create table t as select rownum id, 'test' name from dual connect by level
--alter table t add (x number default 1); =>忽略测试
set timing on
alter table t add (x1 number );
alter table t add (x2 number default NULL);
alter table t add (x3 number default NULL );
alter table t add ( x4 number default NULL);
alter table t add ( x5 number default NULL );
SQL> alter table t add (x1 number );
Table altered.
Elapsed: 00:00:00.11
SQL> alter table t add (x2 number default NULL);
Table altered.
Elapsed: 00:00:00.04
SQL> alter table t add (x3 number default NULL );
Table altered.
Elapsed: 00:02:26.98
SQL> alter table t add ( x4 number default NULL);
Table altered.
Elapsed: 00:00:00.03
SQL> alter table t add ( x5 number default NULL );
Table altered.
Elapsed: 00:01:30.75
drop table t purge ;
create table t as select rownum id, 'test' name from dual connect by level
alter session set events '10046 trace name context forever, level 12';
alter table t add (x3 number default NULL );
alter session set events '10046 trace name context off';
update "T" set "X3"=NULL
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.01 0 1 0 0
Execute 1 11.45 11.53 35 470 244646 100000
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 2 11.45 11.54 35 471 244646 100000
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 5 (recursive depth: 1)
Rows Row Source Operation
------- ---------------------------------------------------
0 UPDATE T (cr=508 pr=28 pw=0 time=9057310 us)
214094 TABLE ACCESS FULL T (cr=451 pr=35 pw=0 time=214178 us)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
db file scattered read 9 0.00 0.00
db file sequential read 3 0.00 0.00
log file switch completion 3 0.16 0.32
********************************************************************************