高难度SQL语句，高手请进！

lqzwch

多谢各位！这个问题已经困扰我好久了，早知道各位这么热心我早提问就好啦！唉，我真是不学无术啊。

lqzwch

前提是计算值不可能为负数，但有可能遇到分子分母同时为0的情况，我改写的代码如下:
insert into B(B1,B2,B3) select T1/decode(T2,0,-1*(T1+1),T2), T1/decode(T3,0,-1*(T1+1),T3),T1/decode(T4,0,-1*(T1+1),T4) from A;
update B set B1=-1 where B1<0;
update B set B2=-1 where B1<0;
update B set B3=-1 where B1<0;

angel518

Who can explain the usage of funcation---decode?
Thanks in advanced!

doni

b = decode(a,v1,t1,v2,t2,...,t0)
explain in C

1. 
   
2. switch (a) {
   
3.   case v1: b = t1; break;
   
4.   case v2: b = t2; break;
   
5.   ....
   
6.   default: b = t0;
   
7. }
   

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explain in Basic

1. 
   
2. select case a
   
3.   case 1:
   
4.      b = t1
   
5.   case 2:
   
6.      b = t2
   
7.   ....
   
8.   else
   
9.      b = t0
   
10. end select
    

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