存储过程中IF嵌套出错，急。

Question

存储过程中IF嵌套出错，新手上路，还望指点下。set @FBillNo_44=(select SUBSTRING(FBillNo,1,2) from Com_BillInventory where  [FID]  = @FID_1)
if @FNote_13="是"
begin
if @FBillNo_44<>'00'
then
 set @FBillNo_44='00'+@FBillNo_44if @FBillNo_44='00'
then
 set @FBillNo_44=@FBillNo_44
endelse
begin
if @FBillNo_44<>'00'
then 
@FBillNo_44=@FBillNo_44
if @FBillNo_44='00'
then
@FBillNo_44=SUBSTRING(@FBillNo_44,3,8)
end提示关键字"then"附近有语法错误。

Answer 1

set @FBillNo_44=(select SUBSTRING(FBillNo,1,2) from Com_BillInventory where  [FID]     = @FID_1)
if @FNote_13="是"
begin
if @FBillNo_44<>'00'
 set @FBillNo_44='00'+@FBillNo_44if @FBillNo_44='00'
 set @FBillNo_44=@FBillNo_44
endelse
begin
if @FBillNo_44<>'00'
@FBillNo_44=@FBillNo_44
if @FBillNo_44='00'
@FBillNo_44=SUBSTRING(@FBillNo_44,3,8)
end

Answer 2

set @FBillNo_44=(select SUBSTRING(FBillNo,1,2) from Com_BillInventory where  [FID]     = @FID_1)
if @FNote_13="是"
begin
if @FBillNo_44<>'00'
 set @FBillNo_44='00'+@FBillNo_44if @FBillNo_44='00'
 set @FBillNo_44=@FBillNo_44
endelse
begin
if @FBillNo_44<>'00'
set @FBillNo_44=@FBillNo_44
if @FBillNo_44='00'
set @FBillNo_44=SUBSTRING(@FBillNo_44,3,8)
end

Answer 3

if 和else对应，不能使用then

Answer 4

IF 1 = 1 
    BEGIN

    END
ELSE 
    BEGIN

    END