restristions for DISTINCT usage

From: Matthias Wirtz <Matthias.Wirtz_at_gmx.net>
Date: Tue, 5 Jul 2005 21:26:49 -0400
Message-ID: <mrGye.53061$iU.27291@lakeread05>

Hi,

just read in the SQL 9i manual about restrictions while using the DISTINCT statement. The whole sections reads as follows:

---

SELECT STATEMENT:
[...]
DISTINCT | UNIQUE
Specify DISTINCT or UNIQUE if you want Oracle to return only one copy of each set of duplicate rows selected (these two keywords are synonymous). Duplicate rows are those with matching values for each expression in the select
list.
Restrictions on DISTINCT and UNIQUE Queries:
#) When you specify DISTINCT or UNIQUE, the total number of bytes in all
select list expressions is limited to the size of a data block minus some overhead. This
size is specified by the initialization parameter DB_BLOCK_SIZE.
#) You cannot specify DISTINCT if the select_list contains LOB columns.

---

The first restriction is somewhat unclear to me: "... the total number of bytes in all select list expression ..."

Is the select string limited? Which bytes are they referring to?

I think the select list expressions are somewhat unclear to. Did someone else come across this section? Thx.

--
Matthias Wirtz  -  Norfolk, USA

Received on Tue Jul 05 2005 - 20:26:49 CDT