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似水��年 — Wed, 05 Apr 2006 05:38:00 GMT

In Oracle/PLSQL, the NVL function lets you substitute a value when a null value is encountered.

The syntax for the NVL function is:

NVL( string1, replace_with )

string1 is the string to test for a null value.

replace_with is the value returned if string1 is null.

Example #1:

select NVL(supplier_city, 'n/a')
from suppliers;

The SQL statement above would return 'n/a' if the supplier_city field contained a null value. Otherwise, it would return the supplier_city value.

Example #2:

select supplier_id,
NVL(supplier_desc, supplier_name)
from suppliers;

This SQL statement would return the supplier_name field if the supplier_desc contained a null value. Otherwise, it would return the supplier_desc.

Example #3:

select NVL(commission, 0)
from sales;

This SQL statement would return 0 if the commission field contained a null value. Otherwise, it would return the commission field.

Frequently Asked Questions

Question: I tried to use the NVL function through VB to access Oracle DB.

To be precise,

select NVL(DIstinct (emp_name),'AAA'),................ from.................

I got an oracle error when I use distinct clause with NVL, but when I remove distinct it works fine.

Answer: It is possible to the use the DISTINCT clause with the NVL function. However, the DISTINCT must come before the use of the NVL function. For example:

select distinct NVL(emp_name, 'AAA')
from employees;

Hope this helps!

Question: Is it possible to use the NVL function with more than one column with the same function call? To be clear, if i need to apply this NVL function to more than one column like this:

NVL(column1;column2 ...... , here is the default value for all )

Answer: You will need to make separate NVL function calls for each column. For example:

select NVL(table_name, 'not found'), NVL(owner, 'not found')
from all_tables;

似水��年 2006-04-05 13:38 发表评论

似水��年 — Tue, 04 Apr 2006 04:51:00 GMT

In Oracle/PLSQL, the decode function has the functionality of an IF-THEN-ELSE statement.

The syntax for the decode function is:

decode( expression , search , result [, search , result]... [, default] )

expression is the value to compare.

search is the value that is compared against expression.

result is the value returned, if expression is equal to search.

default is optional. If no matches are found, the decode will return default. If default is omitted, then the decode statement will return null (if no matches are found).

For Example:

You could use the decode function in an SQL statement as follows:

SELECT supplier_name,

decode(supplier_id, 10000, 'IBM',

10001, 'Microsoft',

10002, 'Hewlett Packard',

'Gateway') result

FROM suppliers;

The above decode statement is equivalent to the following IF-THEN-ELSE statement:

IF supplier_id = 10000 THEN
     result := 'IBM';

ELSIF supplier_id = 10001 THEN
    result := 'Microsoft';

ELSIF supplier_id = 10002 THEN
    result := 'Hewlett Packard';

ELSE
    result := 'Gateway';

END IF;

The decode function will compare each supplier_id value, one by one.

Frequently Asked Questions

Question: One of our viewers wanted to know how to use the decode function to compare two dates (ie: date1 and date2), where if date1 > date2, the decode function should return date2. Otherwise, the decode function should return date1.

Answer: To accomplish this, use the decode function as follows:

decode((date1 - date2) - abs(date1 - date2), 0, date2, date1)

The formula below would equal 0, if date1 is greater than date2:

(date1 - date2) - abs(date1 - date2)

Question: I would like to know if it's possible to use decode for ranges of numbers, ie 1-10 = 'category 1', 11-20 = 'category 2', rather than having to individually decode each number.

Answer: Unfortunately, you can not use the decode for ranges of numbers. However, you can try to create a formula that will evaluate to one number for a given range, and another number for the next range, and so on.

For example:

SELECT supplier_id,

decode(trunc ((supplier_id - 1) / 10), 0, 'category 1',

1, 'category 2',

2, 'category 3',

'unknown') result

FROM suppliers;

In this example, based on the formula:

trunc ((supplier_id - 1) / 10

The formula will evaluate to 0, if the supplier_id is between 1 and 10.
The formula will evaluate to 1, if the supplier_id is between 11 and 20.
The formula will evaluate to 2, if the supplier_id is between 21 and 30.

and so on...

Question: I need to write a decode statement that will return the following:

If yrs_of_service < 1 then return 0.04
If yrs_of_service >= 1 and < 5 then return 0.04
If yrs_of_service > 5 then return 0.06

How can I do this?

Answer: You will need to create a formula that will evaluate to a single number for each one of your ranges.

For example:

SELECT emp_name,

decode(trunc (( yrs_of_service + 3) / 4), 0, 0.04,

1, 0.04,

0.06) as perc_value

FROM employees;

Helpful Tip: One of our viewers suggested combining the SIGN function with the DECODE function as follows:

The date example above could be modified as follows:

DECODE(SIGN(date1-date2), 1, date2, date1)

The SIGN/DECODE combination is also helpful for numeric comparisons e.g. Sales Bonuses

DECODE(SIGN(actual-target), -1, 'NO Bonus for you', 0,'Just made it', 1, 'Congrats, you are a winner')

似水��年 2006-04-04 12:51 发表评论

似水��年 — Tue, 04 Apr 2006 02:33:00 GMT

In Oracle/PLSQL, the to_char function converts a number or date to a string.

The syntax for the to_char function is:

to_char( value, [ format_mask ], [ nls_language ] )

value can either be a number or date that will be converted to a string.

format_mask is optional. This is the format that will be used to convert value to a string.

nls_language is optional. This is the nls language used to convert value to a string.

Examples - Numbers

The following are number examples for the to_char function.

to_char(1210.73, '9999.9') would return '1210.7'

to_char(1210.73, '9,999.99') would return '1,210.73'

to_char(1210.73, '$9,999.00') would return '$1,210.73'

to_char(21, '000099') would return '000021'

Examples - Dates

The following is a list of valid parameters when the to_char function is used to convert a date to a string. These parameters can be used in many combinations.

Parameter Explanation

YEAR Year, spelled out

YYYY 4-digit year

YYY
YY
Y Last 3, 2, or 1 digit(s) of year.

IYY
IY
I Last 3, 2, or 1 digit(s) of ISO year.

IYYY 4-digit year based on the ISO standard

Q Quarter of year (1, 2, 3, 4; JAN-MAR = 1).

MM Month (01-12; JAN = 01).

MON Abbreviated name of month.

MONTH Name of month, padded with blanks to length of 9 characters.

RM Roman numeral month (I-XII; JAN = I).

WW Week of year (1-53) where week 1 starts on the first day of the year and continues to the seventh day of the year.

W Week of month (1-5) where week 1 starts on the first day of the month and ends on the seventh.

IW Week of year (1-52 or 1-53) based on the ISO standard.

D Day of week (1-7).

DAY Name of day.

DD Day of month (1-31).

DDD Day of year (1-366).

DY Abbreviated name of day.

J Julian day; the number of days since January 1, 4712 BC.

HH Hour of day (1-12).

HH12 Hour of day (1-12).

HH24 Hour of day (0-23).

MI Minute (0-59).

SS Second (0-59).

SSSSS Seconds past midnight (0-86399).

FF Fractional seconds.

Parameter	Explanation
YEAR	Year, spelled out
YYYY	4-digit year
YYY YY Y	Last 3, 2, or 1 digit(s) of year.
IYY IY I	Last 3, 2, or 1 digit(s) of ISO year.
IYYY	4-digit year based on the ISO standard
Q	Quarter of year (1, 2, 3, 4; JAN-MAR = 1).
MM	Month (01-12; JAN = 01).
MON	Abbreviated name of month.
MONTH	Name of month, padded with blanks to length of 9 characters.
RM	Roman numeral month (I-XII; JAN = I).
WW	Week of year (1-53) where week 1 starts on the first day of the year and continues to the seventh day of the year.
W	Week of month (1-5) where week 1 starts on the first day of the month and ends on the seventh.
IW	Week of year (1-52 or 1-53) based on the ISO standard.
D	Day of week (1-7).
DAY	Name of day.
DD	Day of month (1-31).
DDD	Day of year (1-366).
DY	Abbreviated name of day.
J	Julian day; the number of days since January 1, 4712 BC.
HH	Hour of day (1-12).
HH12	Hour of day (1-12).
HH24	Hour of day (0-23).
MI	Minute (0-59).
SS	Second (0-59).
SSSSS	Seconds past midnight (0-86399).
FF	Fractional seconds.

The following are date examples for the to_char function.

to_char(sysdate, 'yyyy/mm/dd'); would return '2003/07/09'

to_char(sysdate, 'Month DD, YYYY'); would return 'July 09, 2003'

to_char(sysdate, 'FMMonth DD, YYYY'); would return 'July 9, 2003'

to_char(sysdate, 'MON DDth, YYYY'); would return 'JUL 09TH, 2003'

to_char(sysdate, 'FMMON DDth, YYYY'); would return 'JUL 9TH, 2003'

to_char(sysdate, 'FMMon ddth, YYYY'); would return 'Jul 9th, 2003'

You will notice that in some examples, the format_mask parameter begins with "FM". This means that zeros and blanks are suppressed. This can be seen in the examples below.

to_char(sysdate, 'FMMonth DD, YYYY'); would return 'July 9, 2003'

to_char(sysdate, 'FMMON DDth, YYYY'); would return 'JUL 9TH, 2003'

to_char(sysdate, 'FMMon ddth, YYYY'); would return 'Jul 9th, 2003'

The zeros have been suppressed so that the day component shows as "9" as opposed to "09".

Frequently Asked Questions

Question: Why doesn't this sort the day's of the week in order?

select ename, hiredate, to_char((hiredate),'fmDay') "Day"
from emp
order by "Day";

Answer:

The fmDay parameter will return the name of the Day and not the numeric value of the day.
Try the following:

select ename, hiredate, to_char((hiredate),'fmDD') "Day"
from emp
order by "Day";

似水��年 2006-04-04 10:33 发表评论

似水��年 — Tue, 04 Apr 2006 02:15:00 GMT

In Oracle/PLSQL, the coalesce function returns the first non-null expression in the list. If all expressions evaluate to null, then the coalesce function will return null.

The syntax for the coalesce function is:

coalesce( expr1, expr2, ... expr_n )

For Example:

You could use the coalesce function in an SQL statement as follows:

SELECT coalesce( address1, address2, address3 ) result
FROM suppliers;

The above coalesce statement is equivalent to the following IF-THEN-ELSE statement:

IF address1 is not null THEN
     result := address1;

ELSIF address2 is not null THEN
    result := address2;

ELSIF address3 is not null THEN
    result := address3;

ELSE
    result := null;

END IF;

The coalesce function will compare each value, one by one.

似水��年 2006-04-04 10:15 发表评论

String Functions【Oracle�?转蝲)

似水��年 — Tue, 04 Apr 2006 01:25:00 GMT

ASCII
Get The ASCII Value Of A Character	ASCII()
	SELECT ASCII('A') FROM dual; SELECT ASCII('Z') FROM dual; SELECT ASCII('a') FROM dual; SELECT ASCII('z') FROM dual; SELECT ASCII(' ') FROM dual;

CASE Related Functions
Upper Case	UPPER()
	SELECT UPPER('Dan Morgan') FROM dual;
Lower Case	LOWER()
	SELECT LOWER('Dan Morgan') FROM dual;
Initial Letter Upper Case	INITCAP()
	SELECT INITCAP('DAN MORGAN') FROM dual;
NLS Upper Case	NLS_UPPER()
	SELECT NLS_UPPER('Dan Morgan', 'NLS_SORT = XDanish') FROM dual;
NLS Lower Case	NLS_LOWER()
	SELECT NLS_LOWER('Dan Morgan', 'NLS_SORT = XFrench') FROM dual;
NLS Initial Letter Upper Case	NLS_INITCAP()
	SELECT NLS_INITCAP('DAN MORGAN', 'NLS_SORT = XGerman') FROM dual;

CHR
Character	CHR(>)
	SELECT(CHR(68) \|\| CHR(65) \|\| CHR(78)) FROM dual; SELECT(CHR(68) \|\| CHR(97) \|\| CHR(110)) FROM dual;

COALESCE
Returns the first non-null occurrence	COALESCE(, , , ...)
	CREATE TABLE test ( col1 VARCHAR2(1), col2 VARCHAR2(1), col3 VARCHAR2(1)); INSERT INTO test VALUES (NULL, 'B', 'C'); INSERT INTO test VALUES ('A', NULL, 'C'); INSERT INTO test VALUES (NULL, NULL, 'C'); INSERT INTO test VALUES ('A', 'B', 'C'); SELECT COALESCE(col1, col2, col3) FROM test;

CONCAT
Concatenate	CONCAT(>, >)
	SELECT CONCAT('Dan ', 'Morgan') FROM dual;

CONVERT
Converts From One Character Set To Another	CONVERT(,, )
	SELECT CONVERT('?????A B C D E','US7ASCII','WE8ISO8859P1') FROM dual;

INSTR
See links at page bottom

LENGTH
String Length	LENGTH()
	SELECT LENGTH('Dan Morgan') FROM dual;

LPAD
Left Pad	LPAD(, , )
	SELECT LPAD('Dan Morgan', 25, 'x') FROM dual;

LTRIM
Left Trim	LTRIM()
	SELECT LTRIM(' Dan Morgan ') FROM dual;

NLSSORT
Returns the string of bytes used to sort a string. The string returned is of RAW data type	NLSSORT(, 'NLS_SORT = );
	CREATE TABLE test (name VARCHAR2(15)); INSERT INTO test VALUES ('Gaardiner'); INSERT INTO test VALUES ('Gaberd'); INSERT INTO test VALUES ('G鈈erd'); COMMIT; SELECT * FROM test ORDER BY name; SELECT * FROM test ORDER BY NLSSORT(name, 'NLS_SORT = XDanish');

REPLACE
See links at page bottom

REVERSE
Reverse	REVERSE()
	SELECT REVERSE('Dan Morgan') FROM dual; SELECT DUMP('Dan Morgan') FROM dual; SELECT DUMP(REVERSE('Dan Morgan')) FROM dual;

RPAD
Right Pad	RPAD(, , )
	SELECT RPAD('Dan Morgan', 25, 'x') FROM dual;

RTRIM
Right Trim	RTRIM()
	SELECT RTRIM(' Dan Morgan ') FROM dual;

SOUNDEX
Returns Character String Constaining The Phonetic Representation Of Another String	Rules: Retain the first letter of the string and remove all other occurrences of the following letters: a, e, h, i, o, u, w, y Assign numbers to the remaining letters (after the first) as follows: b, f, p, v = 1 c, g, j, k, q, s, x, z = 2 d, t = 3 l = 4 m, n = 5 r = 6 If two or more letters with the same number were adjacent in the original name (before step 1), or adjacent except for any intervening h and w, then omit all but the first. Return the first four bytes padded with 0. SOUNDEX()
	CREATE TABLE test ( name VARCHAR2(15)); INSERT INTO test VALUES ('Smith'); INSERT INTO test VALUES ('Smyth'); INSERT INTO test VALUES ('Smythe'); INSERT INTO test VALUES ('Smither'); INSERT INTO test VALUES ('Smidt'); INSERT INTO test VALUES ('Smick'); INSERT INTO test VALUES ('Smiff'); COMMIT; SELECT * FROM test; SELECT * FROM test WHERE SOUNDEX(name) = SOUNDEX('SMITH');

SUBSTR
See links at page bottom

TRANSLATE
See links at page bottom

TREAT
Changes The Declared Type Of An Expression	TREAT ( AS REF schema.type))
	SELECT name, TREAT(VALUE(p) AS employee_t).salary SALARY FROM persons p;

TRIM (variations are LTRIM and RTRIM)
Trim Spaces	TRIM()
	SELECT ' Dan Morgan ' FROM dual; SELECT TRIM(' Dan Morgan ') FROM dual;
Trim Other Characters	TRIM( FROM )
	SELECT TRIM('D' FROM 'Dan Morgan') FROM dual;
Trim By CHR value	TRIM()
	SELECT ASCII(SUBSTR('Dan Morgan',1,1)) FROM dual; SELECT TRIM(CHR(68) FROM 'Dan Morgan') FROM dual;

Vertical Bars
Also known as Pipes	\|\|
	SELECT 'Dan' \|\| ' ' \|\| 'Morgan' FROM dual; with alias SELECT 'Dan' \|\| ' ' \|\| 'Morgan' NAME FROM dual; or SELECT 'Dan' \|\| ' ' \|\| 'Morgan' AS NAME FROM dual;

VSIZE
Byte Size	VSIZE()
	SELECT VSIZE('Dan Morgan') FROM dual;

Related Topics

Miscellaneous Functions

似水��年 2006-04-04 09:25 发表评论

似水��年 — Tue, 04 Apr 2006 01:24:00 GMT

In Oracle/PLSQL, the trim function removes all specified characters either from the beginning or the ending of a string.

The syntax for the trim function is:

trim( [ leading | trailing | both [ trim_character ] ] string1 )

leading - remove trim_string from the front of string1.

trailing - remove trim_string from the end of string1.

both - remove trim_string from the front and end of string1.

If none of these are chosen (ie: leading, trailing, both), the trim function will remove trim_string from both the front and end of string1.

trim_character is the character that will be removed from string1. If this parameter is omitted, the trim function will remove all leading and trailing spaces from string1.

string1 is the string to trim.

For example:

trim(' tech ') would return 'tech'

trim(' ' from ' tech ') would return 'tech'

trim(leading '0' from '000123') would return '123'

trim(trailing '1' from 'Tech1') would return 'Tech'

trim(both '1' from '123Tech111') would return '23Tech'

似水��年 2006-04-04 09:24 发表评论

CASE WHEN [Oracle SQL]�Q�链接）

似水��年 — Mon, 03 Apr 2006 09:37:00 GMT

http://www.adp-gmbh.ch/ora/sql/case_when.html

似水��年 2006-04-03 17:37 发表评论

RPAD and LPAD in Oracle�Q�链接）

似水��年 — Mon, 03 Apr 2006 09:10:00 GMT

http://www.adp-gmbh.ch/ora/sql/rpad.html

似水��年 2006-04-03 17:10 发表评论

START WITH and CONNECT BY in Oracle SQL�Q�链接）

似水��年 — Mon, 03 Apr 2006 09:00:00 GMT

http://www.adp-gmbh.ch/ora/sql/connect_by.html

似水��年 2006-04-03 17:00 发表评论

似水��年 — Mon, 03 Apr 2006 08:24:00 GMT

TRUNC()函数分两�U�：

1.TRUNC(for dates)
TRUNC函数为指定元素而截�ȝ��日期倹{�?br /> 其具体的语法格式如下�Q?br /> TRUNC�Q�date[,fmt]�Q?br /> 其中�Q?br /> date 一个日期�?br /> fmt 日期格式�Q�该日期��由指定的元素格式所截去。忽略它则由最�q�的日期截去
下面是该函数的��用情况：
TRUNC�Q�TO_DATE(�?4-Nov-1999 08:00 pm�?’dd-mon-yyyy hh:mi am�?�Q?br /> =�?4-Nov-1999 12:00:00 am�?br /> TRUNC�Q�TO_DATE(�?4-Nov-1999 08:37 pm�?’dd-mon-yyyy hh:mi am�?’hh�?�Q��? =�?4-Nov-1999 08:00:00 am�?br />
2.TRUNC(for number)
TRUNC函数�q�回处理后的数��|��其工作机制与ROUND函数极�ؓ�c�M��Q�只是该函数不对指定��数前或后的部分做相应舍入选择处理�Q�而统�l�截厅R�?br /> 其具体的语法格式如下
TRUNC�Q�number[,decimals]�Q?br /> 其中�Q?br /> number 待做截取处理的数�?br /> decimals 指明需保留��数点后面的位数。可选项�Q�忽略它则截��L��有的��数部分
下面是该函数的��用情况：
TRUNC�Q?9.985�Q?�Q?89.98
TRUNC�Q?9.985�Q?89
TRUNC�Q?9.985�Q?1�Q?80
注意�Q�第二个参数可以��敎ͼ�表示为小数点左边指定位数后面的部分截去，卛_��?记�?

似水��年 2006-04-03 16:24 发表评论

SELECT supplier_name,
decode(supplier_id,	10000,	'IBM',
	10001,	'Microsoft',
	10002,	'Hewlett Packard',
		'Gateway') result
FROM suppliers;

SELECT supplier_id,
decode(trunc ((supplier_id - 1) / 10),	0,	'category 1',
	1,	'category 2',
	2,	'category 3',
		'unknown') result
FROM suppliers;

SELECT emp_name,
decode(trunc (( yrs_of_service + 3) / 4),	0,	0.04,
	1,	0.04,
		0.06) as perc_value
FROM employees;

to_char(1210.73, '9999.9')	would return '1210.7'
to_char(1210.73, '9,999.99')	would return '1,210.73'
to_char(1210.73, '$9,999.00')	would return '$1,210.73'
to_char(21, '000099')	would return '000021'

to_char(sysdate, 'yyyy/mm/dd');	would return '2003/07/09'
to_char(sysdate, 'Month DD, YYYY');	would return 'July 09, 2003'
to_char(sysdate, 'FMMonth DD, YYYY');	would return 'July 9, 2003'
to_char(sysdate, 'MON DDth, YYYY');	would return 'JUL 09TH, 2003'
to_char(sysdate, 'FMMON DDth, YYYY');	would return 'JUL 9TH, 2003'
to_char(sysdate, 'FMMon ddth, YYYY');	would return 'Jul 9th, 2003'

trim(' tech ')	would return 'tech'
trim(' ' from ' tech ')	would return 'tech'
trim(leading '0' from '000123')	would return '123'
trim(trailing '1' from 'Tech1')	would return 'Tech'
trim(both '1' from '123Tech111')	would return '23Tech'