Change column type in table

问题

I have a datatable called deal in Oracle with four columns:
DealID: (PK)
LegID
OrigID
Description

The problem is that if I want to insert a deal with description = A, the attributes LegID and OrigID must be unique, otherwise, there is not problem. How can i make this check? I had thought a trigger after insert. There are more solutions?

Thanks in advance!!

回答1:

You need a function based unique index :

create table tt (
  DealID number(10) primary key,
  LegID number(10),
  OrigID number(10),
  Description varchar2(200 char)
);
create unique index tt_leg_orig_dscr_uk on tt (
  case when description = 'A' then description end,
  case when description = 'A' then legid end,
  case when description = 'A' then origid end
);

insert into tt values (1, 1, 1, 'A');
1 row(s) inserted.

insert into tt values (2, 1, 1, 'A');
ORA-00001: unique constraint (XXXXX.TT_LEG_ORIG_DSCR_UK) violated

insert into tt values (2, 1, 2, 'A');
1 row(s) inserted.

select * from tt;
DEALID  LEGID   ORIGID  DESCRIPTION
-----------------------------------
    1       1        1           A
    2       1        2           A
2 rows returned in 0.01 seconds

insert into tt values (3, 1, 1, 'B');
1 row(s) inserted.

insert into tt values (4, 1, 1, 'B');
1 row(s) inserted.

select * from tt order by 1;

DEALID  LEGID   ORIGID  DESCRIPTION
-----------------------------------
     1      1        1           A
     2      1        2           A
     3      1        1           B
     4      1        1           B
4 rows returned in 0.01 seconds

As you can see, the unique index work only with records with description = 'A', It allows to have non-unique records for different descriptions.

来源：https://stackoverflow.com/questions/24627283/change-column-type-in-table

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sql

database

Oracle

triggers

oracle10g