I am trying to implement a unique constraint for a combination of two columns. I am running oracle 11g.
我正在尝试为两列的组合实现唯一约束。我正在运行oracle 11g。
Specifically I have two columns A and B.
具体来说,我有两列A和B.
I have a row like below
我有一排如下
A B
1 2
Then I want the following combinations to fail when inserted
然后我希望以下组合在插入时失败
A B
1 2
2 1
Is this possible to achieve with a unique index in Oracle?
这可能是通过Oracle中的唯一索引实现的吗?
2 个解决方案
#1
6
Yes, it is possible(for example using generated columns):
是的,它是可能的(例如使用生成的列):
CREATE TABLE tab(A INT NOT NULL, B INT NOT NULL);
ALTER TABLE tab ADD c1 AS (LEAST(A,B));
ALTER TABLE tab ADD c2 AS (GREATEST(A,B));
CREATE UNIQUE INDEX UQ_tab ON tab(c1,c2);
You could hide these columns if needed(Oracle 12c):
如果需要,您可以隐藏这些列(Oracle 12c):
ALTER TABLE tab MODIFY c1 INVISIBLE;
ALTER TABLE tab MODIFY c2 INVISIBLE;
EDIT:
Even simpler approach:
更简单的方法:
CREATE UNIQUE INDEX UQ_tab ON tab(least(A,B), greatest(A,B));
#2
2
You can use a UNIQUE INDEX
with LEAST
, GREATEST
and COALESCE
functions:
您可以使用具有LEAST,GREATEST和COALESCE功能的UNIQUE INDEX:
CREATE TABLE table_name (
a INT,
b INT
);
CREATE UNIQUE INDEX table_name__a__b__u ON TABLE_NAME(
COALESCE( LEAST( a, b ), a, b ),
GREATEST( a, b )
);
You need to include COALESCE
in case one of the values is NULL
.
如果其中一个值为NULL,则需要包含COALESCE。
INSERT INTO table_name ( a, b ) VALUES ( 1, 2 );
1 rows affected
INSERT INTO table_name ( a, b ) VALUES ( 3, NULL );
1 rows affected
INSERT INTO table_name ( a, b ) VALUES ( 2, 1 );
ORA-00001: unique constraint (SCHEMA_NAME.TABLE_NAME__A__B__U) violated
INSERT INTO table_name ( a, b ) VALUES ( NULL, 3 );
ORA-00001: unique constraint (SCHEMA_NAME.TABLE_NAME__A__B__U) violated
#1
6
Yes, it is possible(for example using generated columns):
是的,它是可能的(例如使用生成的列):
CREATE TABLE tab(A INT NOT NULL, B INT NOT NULL);
ALTER TABLE tab ADD c1 AS (LEAST(A,B));
ALTER TABLE tab ADD c2 AS (GREATEST(A,B));
CREATE UNIQUE INDEX UQ_tab ON tab(c1,c2);
You could hide these columns if needed(Oracle 12c):
如果需要,您可以隐藏这些列(Oracle 12c):
ALTER TABLE tab MODIFY c1 INVISIBLE;
ALTER TABLE tab MODIFY c2 INVISIBLE;
EDIT:
Even simpler approach:
更简单的方法:
CREATE UNIQUE INDEX UQ_tab ON tab(least(A,B), greatest(A,B));
#2
2
You can use a UNIQUE INDEX
with LEAST
, GREATEST
and COALESCE
functions:
您可以使用具有LEAST,GREATEST和COALESCE功能的UNIQUE INDEX:
CREATE TABLE table_name (
a INT,
b INT
);
CREATE UNIQUE INDEX table_name__a__b__u ON TABLE_NAME(
COALESCE( LEAST( a, b ), a, b ),
GREATEST( a, b )
);
You need to include COALESCE
in case one of the values is NULL
.
如果其中一个值为NULL,则需要包含COALESCE。
INSERT INTO table_name ( a, b ) VALUES ( 1, 2 );
1 rows affected
INSERT INTO table_name ( a, b ) VALUES ( 3, NULL );
1 rows affected
INSERT INTO table_name ( a, b ) VALUES ( 2, 1 );
ORA-00001: unique constraint (SCHEMA_NAME.TABLE_NAME__A__B__U) violated
INSERT INTO table_name ( a, b ) VALUES ( NULL, 3 );
ORA-00001: unique constraint (SCHEMA_NAME.TABLE_NAME__A__B__U) violated