SQL Tuning - How to avoid TOCHAR function against a date

From: <Cherie_Machler_at_gelco.com>
Date: Mon, 08 Apr 2002 09:56:38 -0800
Message-ID: <F001.0043E9D3.20020408095638@fatcity.com>

I've got the following SQL statement that is running very long on a nightly data load. The problem is the TO_CHAR function which is preventing me from using the index on this small (20,000-row table).

This is an 8.0.4 database so it is not possible for me to use make this a function-based index.

The problem is that the date field has minutes, etc. included and those need to be eliminated before the comparison can be made. That's why I can't just eliminate the TO_CHAR from both sides of the equation.

Isn't there a way that I can pull this function out of the select statement and do it in a preceeding statement? Then I could just pass in both variables to this statement without the TO_CHAR and use my index.

Is this realistic? How, exactly could it be done?

SELECT DATE_KEY
FROM DATE_DIM
WHERE TO_CHAR(ORACLE_DATE,'DD-MON-YYYY') = TO_CHAR(:b1,'DD-MON-YYYY')

SQL> desc date_dim;

 Name                            Null?    Type
 ------------------------------- -------- ----
 DATE_KEY                        NOT NULL NUMBER(5)
 ORACLE_DATE                     NOT NULL DATE
 DATACOM_DATE                             NUMBER(6)
 DATACOM_REVERSE_DATE                     NUMBER(6)
 DAY_OF_WEEK                     NOT NULL VARCHAR2(30)
 DAY_NUMBER_IN_MONTH             NOT NULL NUMBER(3)
 DAY_NUMBER_OVERALL              NOT NULL NUMBER(9)
 WEEK_NUMBER_IN_YEAR             NOT NULL NUMBER(3)
 WEEK_NUMBER_OVERALL             NOT NULL NUMBER(7)
 MONTH                           NOT NULL VARCHAR2(30)
 MONTH_NUMBER_OVERALL            NOT NULL NUMBER(7)
 YEAR                            NOT NULL NUMBER(5)
 WEEKDAY_IND                     NOT NULL CHAR(1)
 LAST_DAY_IN_MONTH_IND           NOT NULL CHAR(1)
 DATA_WAREHOUSE_MOD_DATETIME     NOT NULL DATE
 DATA_MART_MOD_DATETIME          NOT NULL DATE

SQL> select oracle_date from date_dim where rownum=1;

ORACLE_DA

---

01-JAN-70 Thanks in advance for any help.

Cherie Machler
Oracle DBA
Gelco Information Network

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Author:
  INET: Cherie_Machler_at_gelco.com

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