Question

The semantic of our data is case insensitive, so we configure the oracle sessions to be case insensitive:

alter session set NLS_COMP=LINGUISTIC;
alter session set NLS_SORT=BINARY_AI;

Then, to take advantage of indexes we would also want the primary key to be case insensitive as well:

create table SCHEMA_PROPERTY (
  NAME  nvarchar2(64)   not null,
  VALUE nvarchar2(1024),
  constraint SP_PK primary key (nlssort(NAME))
)

However, this runs into “ORA-00904: : invalid identifier”, so I assume it is not possible to use the nlssort() function in the PK definition.

Next attempt was to associate a case-insensitive unique index to the primary key:

create table SCHEMA_PROPERTY (
  NAME  nvarchar2(64) primary key using index (
      create unique index SP_UQ on SCHEMA_PROPERTY(nlssort(NAME))),
  VALUE nvarchar2(1024)
);

but this failed too:

Error: ORA-14196: Specified index cannot be used to enforce the constraint.
14196. 00000 -  "Specified index cannot be used to enforce the constraint."
*Cause:    The index specified to enforce the constraint is unsuitable
           for the purpose.
*Action:   Specify a suitable index or allow one to be built automatically.

Should I just conclude that Oracle does not support case-insensitive semantics for a PK constraint? This works fine in MSSQL which has a simpler approach in dealing with collations.

We could, of course, create a unique index instead of the primary key, but I wanted to make sure first that the normal way to do this is not supported.

Our oracle version is 11.2.0.1.

Answer 1

As you are on 11.2 you can use a virtual column to achieve this:

CREATE TABLE SCHEMA_PROPERTY (
   REAL_NAME  nvarchar2(64) not null,
   NAME       generated always as (lower(real_name)) primary key,
   VALUE nvarchar2(1024)
);