oracle 唯一索引允许为空实验_阿杜

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oracle 唯一索引允许为空实验

(2011-11-04 12:04:55)

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分类： oracle

SQL> create table t1 as select * from dba_objects;

Table created.

SQL> select count(object_id) from dba_objects;

COUNT(OBJECT_ID)
----------------
50103

SQL> select count(distinct object_id) from dba_objects;

COUNT(DISTINCTOBJECT_ID)
------------------------
50103

SQL> update t1 set object_id='' where object_id >100 and object_id <105;

4 rows updated.

SQL> commit;

Commit complete.

SQL> create unique index idx_object_id on t1(object_id);

Index created.

SQL>

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