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行列转换实例
                  表ttt有三个字段
                  seq  
--序列
                  jcxm --检查项目
                  zhi  --

                  数据分别如下:
                  seq   jcxm       zhi
                  
-------      --------          --------
                  11     1    0.50
                  
11     2    0.21
                  
11     3    0.25
                  
12     1    0.24
                  
12     2    0.30
                  
12     3    0.22                             

                  实现功能
                  创建视图时移动行值为列值


                  
create view v_view1
                  
as
                  
select seq,
                         
sum(decode(jcxm,1, zhi)) 检测项目1,
                         
sum(decode(jcxm,2, zhi)) 检测项目2, 
                         
sum(decode(jcxm,3, zhi)) 检测项目3 
                  
from ttt
                  
group by seq;

                  序号 检测项目1  检测项目2  检测项目3
                  
11     0.50    0.21     0.25
                  
12     0.24    0.30     0.22

 

                  技巧:
                  用THEN中的0和1来进行统计(
SUM

                  jcxm   zhi
                  
----   ----
                  a           1
                  b           
1
                  a           
3
                  d           
2
                  e           
4
                  f           
5
                  a           
5
                  d           
3
                  d           
6
                  b           
5
                  c           
4
                  b           
3
                  求他的zhi既是1,也是3,也是5的jcxm
                  方法一
                  
select jcxm
                  
from ttt
                  
group by jcxm
                  
having sum(decode(zhi,1,-1,3,-1,5,-1,0)) = -3
                  方法二
                  
select jcxm from ttt 
                  
group by jcxm having (sign(sum(decode(zhi,1,-1,0)))+
                  
sign(sum(decode(zhi,3,-1,0)))+sign(sum(decode(zhi,5,-1,0)))<=-3);

                  
----------
                  a
                  b
                  说明:
                  
sign()函数根据某个值是0、正数还是负数,分别返回0、1-1
                  所以可以用sign和decode来完成比较字段大小来区某个字段
                  
select decode(sign(字段1-字段2),-1,字段3,字段4) from dual;

                  sign是一个对于写分析SQL有很强大的功能
                  下面我对sign进行一些总结:
                  但属性student取0和1以外的值,或者student取两个以上的标法值,问题就不会这么简单了
                  解决办法就是特征函数(
abs(),sign())

                  常用的特征算法
                  [A=B]=
1abssign(A-B))
                  [A!=B]=
abssign(A-B)) 
                  [A
<B]=1sign1sign(A-B)) 
                  不能用
-sign(A-B):因为如果不满足A<b则返回-1,而不是0,这样就不能用在字段选择上了
                  [A
<=B]=sign(1sign(A-B))
                  [A
>B]=1sign1sign(A-B))
                  [A
>=B]=sign(1sign(A-B)))
                  [NOTα]=
1-d [α]
                  [αANDb ]=d [α]
*d [b ] (6)
                  [αOR b ]=
sign(d [α]+d []

                  例如:
                  A
<B                         Decode( Sign(A-B), -110 )      
                     
                  A
<=B                         Decode( Sign(A-B), 101 )      
                     
                  A
>B                         Decode( Sign(A-B), 110 )       
                    
                  A
>=B                         Decode( Sign(A-B), -101 )     
                      
                  A
=B                         Decode( A, B, 10 )         
                  A 
between B and C      Decode( Sign(A-B), -10
                  Decode(
Sign(A-C), 101 ))         
                  A 
is null                       Decode(A,null,1,0)         
                  A 
is not null                 Decode(A,null,0,1)         A in 
                  (B1,B2,,Bn)  Decode(A,B1,
1,B2,1,,Bn,1,0)         
                  nor LogA                    Decode( LogA, 
010 )            
                    (
1-Sign(LogA)) 
                  LogA 
and LogB            LogA * LogB 
                  LogA 
or LogB              LogA + LogB 
                  LogA xor LogB            Decode(
Sign(LogA),Sign(LogB),0,1)    
                  Mod(
Sign(LogA),Sign(LogB),2


                  
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

                  
[NextPage]
                  另外一个关于成绩的分析例子

                  
SELECT
                  
SUM(CASE WHEN cj <60 THEN 1 ELSE 0 ENDas "not passed",
                  
SUM(CASE WHEN cj BETWEEN 60 AND 79 THEN 1 ELSE 0 ENDas 
                  "passed",
                  
SUM(CASE WHEN cj BETWEEN 80 AND 89 THEN 1 ELSE 0 ENDas 
                  "good",
                  
SUM(CASE WHEN cj >=90 THEN 1 ELSE 0 ENDas "Excellent"
                  
FROM cjtable;

                  decode用法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);

                  体会:要用decode 
/group by/ order by/sign/sum来实现不同报表的生成 
                  
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
                  CASE应用

                  
1        1        部门a        800        男
                  
2        2        部门b        900        女
                  
3        3        部门a        400        男
                  
4        4        部门d        1400        女
                  
5        5        部门e        1200        男
                  
6        6        部门f        500        男
                  
7        7        部门a        300        女
                  
8        8        部门d        1000        男
                  
9        9        部门d        1230        女
                  
10        10        部门b        2000        女
                  
11        11        部门c        2000        男
                  
12        12        部门b        1200        男

                    
SELECT jcxm as 部门,COUNT(seq) as 人数,
                      
SUM(CASE SEX WHEN 1 THEN 1 ELSE 0 ENDas 男,
                            
SUM(CASE SEX WHEN 2 THEN 1 ELSE 0 ENDas 女,
                      
SUM(CASE SIGN(zhi-800WHEN -1 THEN 1 ELSE 0 ENDas 
                  小于800元,
                      
SUM((CASE SIGN(zhi-800)*SIGN(zhi-1000)                    
                  
/*用*来实现<和>功能*/
                           
WHEN -1 THEN 1 ELSE 0 END)+(CASE zhi
                           
WHEN 800  THEN 1 ELSE 0 END)) as 从800至999,         
                  
/*注意别名不能以数字开头*/
                      
SUM((CASE SIGN(zhi-1000)*SIGN(zhi-1200)
                           
WHEN -1 THEN 1 ELSE 0 END)+(CASE zhi
                           
WHEN 1000 THEN 1 ELSE 0 END)) as 从1000元至1199元,
                      
SUM((CASE SIGN(zhi-1200WHEN 1 THEN 1 ELSE 0 END)
                      
+(CASE zhi WHEN 1200 THEN 1 ELSE 0 END)) as 大于1200元
                  
FroM ttt 
                  
GROUP BY jcxm

                  部门名 人数    男       女   小于800元 从800至999 从1000元至1199元   大于1200元
                  部门a        
3        2        1        2        1           0   
                                             
0
                  部门b        
3        1        2        0        1           0   
                                             
2
                  部门c        
1        1        0        0        0           0   
                                            
1
                  部门d        
3        1        2        0        0           1   
                                            
2
                  部门e        
1        1        0        0        0             0 
                                              
1
                  部门f        
1        1        0        1        0           0   
                                            
0

posted on 2006-02-10 20:22  LDAR泄漏检测与修复  阅读(4474)  评论(0编辑  收藏  举报