Horton

Re: Covering Indexes

Thomas Munro <munro@ip9.org>

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From: Thomas Munro <munro@ip9.org>
To: Rob Wultsch <wultsch@gmail.com>
Cc: "David E. Wheeler" <david@justatheory.com>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2012-06-30T10:12:09Z
Lists: pgsql-hackers 
On 28 June 2012 14:02, Rob Wultsch <wultsch@gmail.com> wrote:
> On Thu, Jun 28, 2012 at 8:16 AM, David E. Wheeler <david@justatheory.com> wrote:
>> I'm particularly intrigued by "covering indexes". For example:
>>
>>    CREATE INDEX cover1 ON table1(a,b) COVERING(c,d);
>
> IRC MS SQL also allow unindexed columns in the index.

For what it's worth, DB2 also has this feature, written roughly the
same way as MS SQL Server: CREATE INDEX cover1 ON table1(a, b) INCLUDE
(c, d).

http://pic.dhe.ibm.com/infocenter/db2luw/v9r7/index.jsp?topic=/com.ibm.db2.luw.sql.ref.doc/doc/r0000919.html

Oracle doesn't seem to have this feature (and the SQL standard doesn't
mention indexes at all).