同事問及關(guān)于rownum表記錄不顯示問題,經(jīng)查閱官方手冊(cè),附上測(cè)試筆記:

SQL> insert into t_rownum select level from dual connect by level<=5;

5 rows inserted

SQL> commit;

Commit complete

SQL> select * from t_rownum;

A

---------------------------------------

1

2

3

4

5

SQL> select * from t_rownum where rownum>0;

A

---------------------------------------

1

2

3

4

5

SQL> select * from t_rownum where rownum>=0;

A

---------------------------------------

1

2

3

4

5

SQL> select * from t_rownum where rownum>=1;

A

---------------------------------------

1

2

3

4

5

SQL> select * from t_rownum where rownum>=2;

A

---------------------------------------

SQL> select * from t_rownum where rownum>2;

A

---------------------------------------

SQL>

官方手冊(cè)源語:

Conditions testing for ROWNUM values greater than a positive integer are always false. For example, this query returns no rows:SELECT *

FROM employees

WHERE ROWNUM > 1;

The first row fetched is assigned a ROWNUM of 1 and makes the condition false. The second row to be fetched is now the first row and is also assigned a ROWNUM of 1 and makes the condition false. All rows subsequently fail to satisfy the condition, so no rows are returned.

You can also use ROWNUM to assign unique values to each row of a table, as in this example:UPDATE my_table

SET column1 = ROWNUM;總而述之:oracle會(huì)對(duì)提取的記錄一一比較是否符合where條件,故不會(huì)顯示記錄

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