decode

hktais.biz.build.building.dao.mao.Building.xml
     decode(B.PBL_VISIBLE,'1','Yes','No') as IS_PUBLIC

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).



Applies To:

Oracle 9i, Oracle 10g, Oracle 11g


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

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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)


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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...


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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

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;





decode()函數使用技巧
·软件环境：
1、Windows NT4.0+ORACLE 8.0.4
2、ORACLE安装路径为：C:ORANT
·含义解释：
decode(条件,值1,翻译值1,值2,翻译值2,...值n,翻译值n,缺省值)

该函数的含义如下：
IF 条件=值1 THEN
　　　　RETURN(翻译值1)
ELSIF 条件=值2 THEN
　　　　RETURN(翻译值2)
　　　　......
ELSIF 条件=值n THEN
　　　　RETURN(翻译值n)

ELSE
　　　　RETURN(缺省值)
END IF
·        使用方法：
1、比较大小
select decode(sign(变量1-变量2),-1,变量1,变量2) from dual; --取较小值
sign()函数根据某个值是0、正数还是负数，分别返回0、1、-1

例如：
变量1=10，变量2=20
则sign(变量1-变量2)返回-1，decode解码结果为“变量1”，达到了取较小值的目的。


2、表、视图结构转化
现有一个商品销售表sale，表结构为：
month　　　 char(6)　　　　　 --月份
sell　　　　number(10,2)　　　--月销售金额

现有数据为：
200001　　1000
200002　　1100
200003　　1200
200004　　1300
200005　　1400
200006　　1500
200007　　1600
200101　　1100
200202　　1200
200301　　1300

想要转化为以下结构的数据：
year　　　char(4)　　　　　 --年份
month1　　number(10,2)　　　--1月销售金额
month2　　number(10,2)　　　--2月销售金额
month3　　number(10,2)　　　--3月销售金额
month4　　number(10,2)　　　--4月销售金额
month5　　number(10,2)　　　--5月销售金额
month6　　number(10,2)　　　--6月销售金额
month7　　number(10,2)　　　--7月销售金额
month8　　number(10,2)　　　--8月销售金额
month9　　number(10,2)　　　--9月销售金额
month10　　number(10,2)　　　--10月销售金额
month11　　number(10,2)　　　--11月销售金额
month12　　number(10,2)　　　--12月销售金额

结构转化的SQL语句为：
create or replace view
v_sale(year,month1,month2,month3,month4,month5,month6,month7,month8,month9,month10,month11,month12)
as
　　　　select
　　　　substrb(month,1,4),
　　　　sum(decode(substrb(month,5,2),'01',sell,0)),
　　　　sum(decode(substrb(month,5,2),'02',sell,0)),
　　　　sum(decode(substrb(month,5,2),'03',sell,0)),
　　　　sum(decode(substrb(month,5,2),'04',sell,0)),
　　　　sum(decode(substrb(month,5,2),'05',sell,0)),
　　　　sum(decode(substrb(month,5,2),'06',sell,0)),
　　　　sum(decode(substrb(month,5,2),'07',sell,0)),
　　　　sum(decode(substrb(month,5,2),'08',sell,0)),
　　　　sum(decode(substrb(month,5,2),'09',sell,0)),
　　　　sum(decode(substrb(month,5,2),'10',sell,0)),
　　　　sum(decode(substrb(month,5,2),'11',sell,0)),
　　　　sum(decode(substrb(month,5,2),'12',sell,0))
　　　　from sale
　　　　group by substrb(month,1,4);