请问这条奇怪的语句是什么意思？？？？

Question

语句如下：INSERT INTO TM_B_REALBILLSELECT B.SUBSCRBID,
sum(decode(BillITypeID,FEE01,FEE,0)),
sum(decode(BillITypeID,FEE02,FEE,0)), 
sum(decode(BillITypeID,FEE03,FEE,0)),
sum(decode(BillITypeID,FEE04,FEE,0))FROM cas_hlj.tab_billdetail B ,TM_D_ACCT CWHERE c.ACCTITMTYPEID = b.ACCTITMTYPEID;解释越详细越好。。
可以给分多多  ：）

Answer 1

简单的插入语句
就是插入表TM_B_REALBILL
记录来源为select语句,具体就是SELECT B.SUBSCRBID,
sum(decode(BillITypeID,FEE01,FEE,0)),
sum(decode(BillITypeID,FEE02,FEE,0)), 
sum(decode(BillITypeID,FEE03,FEE,0)),
sum(decode(BillITypeID,FEE04,FEE,0))FROM cas_hlj.tab_billdetail B ,TM_D_ACCT CWHERE c.ACCTITMTYPEID = b.ACCTITMTYPEID

Answer 2

INSERT INTO TM_B_REALBILL 
SELECT  
把查询结果插入表TM_B_REALBILL sum 求和函数decode(BillITypeID,FEE01,FEE,0) BillITypeID=FEE01时 取FEE,否则取0
下面几句与此类似FROM cas_hlj.tab_billdetail B ,TM_D_ACCT C
WHERE c.ACCTITMTYPEID = b.ACCTITMTYPEID;
b,c两个表连接，连接字段是ACCTITMTYPEID 

Answer 3

INSERT INTO TM_B_REALBILLSELECT B.SUBSCRBID,
       sum(decode(BillITypeID,FEE01,FEE,0)),
       sum(decode(BillITypeID,FEE02,FEE,0)), 
       sum(decode(BillITypeID,FEE03,FEE,0)),
       sum(decode(BillITypeID,FEE04,FEE,0))FROM cas_hlj.tab_billdetail B ,TM_D_ACCT CWHERE c.ACCTITMTYPEID = b.ACCTITMTYPEID;若没有特别的说明是不是在select语句中的列数要与表TM_B_REALBILL中的列数相同啊。