Oracle 9i tips n tricks documents for Performance Tuning

[user71408]

Hi All,

Can any one please send me the documents for Oracle9i and Performance tuning.

Thank you.

[atulart2]

Oracle Date Functions
Version 11.1

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If so the "Database Essentials" class will begin November 19, 2007 at SQL University ... Try the free Sample Courses and then check out the list of classes and topics. The first class covers materials in the library, including this page, with live demos in SQL*Plus.

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Date
Current Date CURRENT_DATE
SYSDATE
SELECT TO_CHAR(CURRENT_DATE, 'DD-MON-YYYY HH:MI:SS') FROM dual;

SELECT TO_CHAR(SYSDATE, 'DD-MON-YYYY HH:MI:SS') FROM dual;
Formats Day Month Year Fill Mode Julian Date
D MM YY FM J
DD MON YYYY
DDTH RR
DAY RRRR


+ AND -
+ <date> + <integer>
SELECT SYSDATE + 1 FROM dual;
- <date> - <integer>
SELECT SYSDATE - 1 FROM dual;

ADD_MONTHS

Add A Month To A Date ADD_MONTHS(<date>, <number of months_integer>
SELECT add_months(SYSDATE, 2) FROM dual;

-- but be aware of what it is doing
SELECT add_months(TO_DATE('27-JAN-2007'), 1) FROM dual;

SELECT add_months(TO_DATE('28-JAN-2007'), 1) FROM dual;

SELECT add_months(TO_DATE('29-JAN-2007'), 1) FROM dual;

SELECT add_months(TO_DATE('30-JAN-2007'), 1) FROM dual;

SELECT add_months(TO_DATE('31-JAN-2007'), 1) FROM dual;

SELECT add_months(TO_DATE('01-FEB-2007'), 1) FROM dual;

CURRENT_DATE

Returns the current date of the server as a value in the Gregorian calendar of datatype DATE
col sessiontimezone format a30

SELECT sessiontimezone, current_date
FROM dual;

ALTER SESSION SET TIME_ZONE = '-5:0';

SELECT sessiontimezone, current_date
FROM dual;

ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';

SELECT sessiontimezone, current_date
FROM dual;

ALTER SESSION SET TIME_ZONE = '-7:0';

SELECT sessiontimezone, current_date
FROM dual;

ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY';

DUMP
Returns The Number Of Bytes And Datatype Of A Value DUMP(<value>)
SELECT DUMP(SYSDATE) FROM dual;

GREATEST

Return the Latest Date LEAST(<date>, <date>, <date>, ...)
CREATE TABLE t (
datecol1 DATE,
datecol2 DATE,
datecol3 DATE)
PCTFREE 0;

INSERT INTO t VALUES (SYSDATE+23, SYSDATE-10, SYSDATE-24);
INSERT INTO t VALUES (SYSDATE-15, SYSDATE, SYSDATE+15);
INSERT INTO t VALUES (SYSDATE-7, SYSDATE-18, SYSDATE-9);
COMMIT;

SELECT * FROM t;

SELECT GREATEST(datecol1, datecol2, datecol3)
FROM t;

INTERVAL

Interval to adjust date-time INTERVAL '<integer>' <unit>
SELECT TO_CHAR(SYSDATE, 'HH:MI:SS')
FROM dual;

SELECT TO_CHAR(SYSDATE + INTERVAL '10' MINUTE, 'HH:MI:SS')
FROM dual;

SELECT TO_CHAR(SYSDATE - INTERVAL '10' MINUTE, 'HH:MI:SS')
FROM dual;

LAST_DAY
Returns The Last Date Of A Month LAST_DAY(<date>)
SELECT * FROM t;

SELECT LAST_DAY(datecol1) FROM t;

LEAST
Return the Earliest Date LEAST(<date>, <date>, <date>, ...)
SELECT * FROM t;

SELECT LEAST(datecol1, datecol2, datecol3) FROM t;

LENGTH
Returns length in characters LENGTH(<date>)
SELECT LENGTH(last_ddl_time) FROM user_objects;

LENGTHB
Returns length in bytes LENGTHB(<date>)
SELECT LENGTHB(last_ddl_time) FROM user_objects;
Note: Additional forms of LENGTH (LENGTHC, LENGTH2, and LENGTH4) are also available.

MAX
Return the Latest Date MAX(<date>)
SELECT * FROM t;

SELECT MAX(datecol1) FROM t;

MIN
Return the Earliest Date MIN(<date>)
SELECT * FROM t;

SELECT MIN(datecol1) FROM t;

MONTHS_BETWEEN
Returns The Months Separating Two Dates MONTHS_BETWEEN(<latest_date>, <earliest_date>)
SELECT MONTHS_BETWEEN(SYSDATE+365, SYSDATE-365) FROM dual;

SELECT MONTHS_BETWEEN(SYSDATE-365, SYSDATE+365) FROM dual;

NEW_TIME

Returns the date and time in time zone zone2 when date and time in time zone zone1 are date Before using this function, you must set the NLS_DATE_FORMAT parameter to display 24-hour time.
SELECT NEW_TIME(TO_DATE('11-10-99 01:23:45',
'MM-DD-YY HH24:MI:SS'), 'AST', 'PST') "New Date and Time"
FROM dual;

ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';

SELECT NEW_TIME(TO_DATE('11-10-99 01:23:45',
'MM-DD-YY HH24:MI:SS'), 'AST', 'PST') "New Date and Time"
FROM dual;

ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY';

NEXT_DAY
Date of next specified date following a date NEXT_DAY(<date>, <day of the week>)

Options are SUN, MON, TUE, WED, THU, FRI, and SAT
SELECT NEXT_DAY(SYSDATE, 'FRI') FROM dual;

ROUND
Returns date rounded to the unit specified by the format model. If you omit the format, the date is rounded to the nearest day ROUND(<date_value>, <format>)
SELECT ROUND(TO_DATE('27-OCT-00'),'YEAR') NEW_YEAR
FROM dual;

Spelled Out Using TO_CHAR

Spelled Demo DDSP HH24SP MISP MMSP SSSP

SELECT TO_CHAR(TO_DATE('10:30:18', 'HH24:MI:SS'), 'HH24SP:MISP:SSSP')
FROM dual;

SELECT TO_CHAR(TO_DATE('01-JAN-2008', 'DD-MON-YYYY'), 'DDSP-MONTH-YYYYSP')
FROM dual;

SELECT TO_CHAR(TO_DATE('01-JAN-2008', 'DD-MM-YYYY'), 'DDSP-MMSP-YYYYSP')
FROM dual;

SYSDATE
Returns the current session DateTime SYSDATE
SELECT SYSDATE FROM dual;

TRUNC

Convert a date to the date at midnight TRUNC(<date_time>)
CREATE TABLE t (
datecol DATE);

INSERT INTO t (datecol) VALUES (SYSDATE);

INSERT INTO t (datecol) VALUES (TRUNC(SYSDATE));

INSERT INTO t (datecol) VALUES (TRUNC(SYSDATE, 'HH'));

INSERT INTO t (datecol) VALUES (TRUNC(SYSDATE, 'MI'));

COMMIT;

SELECT TO_CHAR(datecol, 'DD-MON-YYYY HH:MI:SS')
FROM t;

Selectively remove part of the date information

Special thanks to Dave Hayes for reminding me of this. TRUNC(<date_time>, '<format>')
SELECT TO_CHAR(SYSDATE, 'DD-MON-YYYY HH:MI:SS')
FROM dual;

-- first day of the month
SELECT TO_CHAR(TRUNC(SYSDATE, 'MM'), 'DD-MON-YYYY HH:MI:SS')
FROM dual;

SELECT TO_CHAR(TRUNC(SYSDATE, 'MON'), 'DD-MON-YYYY HH:MI:SS')
FROM dual;

SELECT TO_CHAR(TRUNC(SYSDATE, 'MONTH'), 'DD-MON-YYYY HH:MI:SS')
FROM dual;

-- first day of the year
SELECT TO_CHAR(TRUNC(SYSDATE, 'YYYY'), 'DD-MON-YYYY HH:MI:SS')
FROM dual;

SELECT TO_CHAR(TRUNC(SYSDATE, 'YEAR'), 'DD-MON-YYYY HH:MI:SS')
FROM dual;

Dates in WHERE Clause Joins SELECT SYSDATE FROM dual;

ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';

SELECT SYSDATE FROM dual;

/

/

ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY';

CREATE TABLE t (
datecol DATE);

INSERT INTO t
(datecol)
VALUES
(SYSDATE);

SELECT * FROM t;

ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';

SELECT * FROM t;

ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY';

SELECT * FROM t;

SELECT SYSDATE FROM dual;

SELECT * FROM t
WHERE datecol = SYSDATE;

ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY HH24:MI:SS';

SELECT * FROM t;

SELECT SYSDATE FROM dual;

SELECT TRUNC(SYSDATE) FROM dual;

SELECT * FROM t
WHERE TRUNC(datecol) = TRUNC(SYSDATE);

ALTER SESSION SET NLS_DATE_FORMAT = 'DD-MON-YYYY';

VSIZE
Returns The Number Of Bytes Required By A Value VSIZE(e IN DATE) RETURN NUMBER
SELECT VSIZE(SYSDATE) FROM dual;

Date Calculations

Returns A Day A Specified Number Of Days In The Future Skipping Weekends CREATE OR REPLACE FUNCTION business_date (start_date DATE,
Days2Add NUMBER) RETURN DATE IS
Counter NATURAL := 0;
CurDate DATE := start_date;
DayNum POSITIVE;
SkipCntr NATURAL := 0;
BEGIN
WHILE Counter < Days2Add LOOP
CurDate := CurDate+1;
DayNum := TO_CHAR(CurDate, 'D');

IF DayNum BETWEEN 2 AND 6 THEN
Counter := Counter + 1;
ELSE
SkipCntr := SkipCntr + 1;
END IF;
END LOOP;
RETURN start_date + Counter + SkipCntr;
END business_date;
/

Business Date function, above, enhanced by Larry Benton to handle negative values for the days2add parameter. CREATE OR REPLACE FUNCTION business_date (start_date DATE,
days2add NUMBER) RETURN DATE IS
Counter NATURAL := 0;
CurDate DATE := start_date;
DayNum POSITIVE;
SkipCntr NATURAL := 0;
Direction INTEGER := 1; -- days after start_date
BusinessDays NUMBER := Days2Add;
BEGIN
IF Days2Add < 0 THEN
Direction := - 1; -- days before start_date
BusinessDays := (-1) * BusinessDays;
END IF;

WHILE Counter < BusinessDays LOOP
CurDate := CurDate + Direction;
DayNum := TO_CHAR( CurDate, 'D');

IF DayNum BETWEEN 2 AND 6 THEN
Counter := Counter + 1;
ELSE
SkipCntr := SkipCntr + 1;
END IF;
END LOOP;

RETURN start_date + (Direction * (Counter + SkipCntr));
END business_date;
/

Returns The First Day Of A Month CREATE OR REPLACE FUNCTION fday_ofmonth(value_in DATE)
RETURN DATE IS
vMo VARCHAR2(2);
vYr VARCHAR2(4);
BEGIN
vMo := TO_CHAR(value_in, 'MM');
vYr := TO_CHAR(value_in, 'YYYY');
RETURN TO_DATE(vMo || '-01-' || vYr, 'MM-DD-YYYY');
EXCEPTION
WHEN OTHERS THEN
RETURN TO_DATE('01-01-1900', 'MM-DD-YYYY');
END fday_ofmonth;
/

Time Calculations

Returns The Number Of Seconds Between Two Date-Time Values CREATE OR REPLACE FUNCTION time_diff (
DATE_1 IN DATE, DATE_2 IN DATE) RETURN NUMBER IS

NDATE_1 NUMBER;
NDATE_2 NUMBER;
NSECOND_1 NUMBER(5,0);
NSECOND_2 NUMBER(5,0);

BEGIN
-- Get Julian date number from first date (DATE_1)
NDATE_1 := TO_NUMBER(TO_CHAR(DATE_1, 'J'));

-- Get Julian date number from second date (DATE_2)
NDATE_2 := TO_NUMBER(TO_CHAR(DATE_2, 'J'));

-- Get seconds since midnight from first date (DATE_1)
NSECOND_1 := TO_NUMBER(TO_CHAR(DATE_1, 'SSSSS'));

-- Get seconds since midnight from second date (DATE_2)
NSECOND_2 := TO_NUMBER(TO_CHAR(DATE_2, 'SSSSS'));

RETURN (((NDATE_2 - NDATE_1) * 86400)+(NSECOND_2 - NSECOND_1));
END time_diff;
/
Calculating time from seconds

Posted by John K. Hinsdale
12/30/06 to c.d.o.misc SELECT DECODE(FLOOR(999999/86400), 0, '',
FLOOR(999999/86400) || ' day(s), ') ||
TO_CHAR(TO_DATE(MOD(999999, 86400),'SSSSS'), 'HH24:MI:SS') AS elapsed
FROM dual;


Related Topics
Cast
Conversion Functions
Miscellaneous Functions
Numeric Functions
String Functions
Timestamp