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SQL> create table t( a int primary key);
Table created
SQL> create unique index on t(a);
create unique index on t(a)
ORA-00953: 索引名缺失或无效
SQL> create unique index b on t(a);
create unique index b on t(a)
ORA-01408: 此列列表已索引
SQL> create table emp1
2 as
3 select * from emp;
Table created
SQL> create unique index idx_emp1_1 on emp1(empno);
Index created
SQL> create unique index idx_emp1_2 on emp1(empno);
create unique index idx_emp1_2 on emp1(empno)
ORA-01408: such column list already indexed
SQL>
SQL> create table t(
2 x number(2),
3 y varchar2(5))
4 /
Table created
SQL> alter table t add constraint pk_t primary key(x);
Table altered
SQL> select constraint_name,table_name,index_name
2 from user_constraints where table_name='T';
CONSTRAINT_NAME TABLE_NAME INDEX_NAME
------------------------------ ------------------------------ ------------------------------
PK_T T PK_T
SQL> select index_name,index_type,table_name,uniqueness
2 from user_indexes where table_name='T';
INDEX_NAME INDEX_TYPE TABLE_NAME UNIQUENESS
------------------------------ --------------------------- ------------------------------ ----------
PK_T NORMAL T UNIQUE
---
SQL> desc user_indexes;
Name Type Nullable Default Comments
----------------------- -------------- -------- ------- --------------------------------------------------------------------------------------
INDEX_NAME VARCHAR2(30) Name of the index
INDEX_TYPE VARCHAR2(27) Y
TABLE_OWNER VARCHAR2(30) Owner of the indexed object
TABLE_NAME VARCHAR2(30) Name of the indexed object
TABLE_TYPE VARCHAR2(11) Y Type of the indexed object
UNIQUENESS VARCHAR2(9) Y Uniqueness status of the index: "UNIQUE", "NONUNIQUE", or "BITMAP"
...