《Truncate table one or million rows》

摘要:《Truncate table one or million rows》

See a problem on itPUB, whim want to verify;

The question is how much time truncate table to millions of pieces of data, the moderator asked how much time you want to truncate table 2 pen data.

My teacher said truncate table is the high water mark from a high return back into place, the data is not deleted;

That time should truncate table, like it! Do a little experiment!

SQL> CREATE TABLE TINGTEST AS SELECT * FROM DBA_OBJECTS;

已建立表格.

SQL> CREATE TABLE TINGTEST2 AS SELECT * FROM DBA_OBJECTS WHERE ROWNUM<2;

已建立表格.

SQL> SELECT COUNT(*)  FROM TINGTEST;

  COUNT(*)
----------
     44264

SQL> INSERT INTO TINGTEST SELECT * FROM TINGTEST;

已建立 44264 个数据列.

SQL> INSERT INTO TINGTEST SELECT * FROM TINGTEST;

已建立 88528 个数据列.

SQL> INSERT INTO TINGTEST SELECT * FROM TINGTEST;

已建立 177056 个数据列.

SQL> INSERT INTO TINGTEST SELECT * FROM TINGTEST;

已建立 354112 个数据列.

SQL> INSERT INTO TINGTEST SELECT * FROM TINGTEST;

已建立 708224 个数据列.

SQL> INSERT INTO TINGTEST SELECT * FROM TINGTEST;

已建立 1416448 个数据列.

SQL> INSERT INTO TINGTEST SELECT * FROM TINGTEST;

已建立 2832896 个数据列.

SQL> COMMIT;

确认完成.

SQL> SELECT COUNT(*) FROM TINGTEST;

  COUNT(*)
----------
   5665792

SQL> SELECT COUNT(*) FROM TINGTEST2;

  COUNT(*)
----------
         1

SQL> SET TIMING ON
SQL> TRUNCATE TABLE TINGTEST;

表格被截断.

目前历时: 00:00:00.02
SQL> TRUNCATE TABLE TINGTEST2;

表格被截断.

目前历时: 00:00:00.00

It seems summarize large data table is quite slow, but very quickly is an indisputable fact!

Original: Big Box  "Truncate table one or million rows"