Plsql P/L SQL中案例中的IF语句

我试图在案例中编写IF语句，但这给了我编译错误。这是我的代码

(CASE 
    IF (acc_type_id_ = 'ENDU') THEN
      WHEN PRODUCT_ID !=  product_id_ AND AVAIL_TO_SELL = 'YES' AND Enable_Add_To_Cart(PRODUCT_ID)='YES' AND PROD_ITEM_PKG.Get_Allow_Endu_Purch(PRODUCT_ID)='YES' THEN '&ACTION_ADD_TO_CART'                               
      WHEN PRODUCT_ID =  product_id_ AND AVAIL_TO_SELL = 'YES' AND Enable_Add_To_Cart(PRODUCT_ID)='YES' AND SELL_ONLY_LINKED != 'YES' AND PROD_ITEM_PKG.Get_Allow_Endu_Purch(PRODUCT_ID)='YES' THEN '&ACTION_ADD_TO_CART' 
    ELSE
       WHEN PRODUCT_ID !=  product_id_ AND AVAIL_TO_SELL = 'YES' AND Enable_Add_To_Cart(PRODUCT_ID)='YES' THEN '&ACTION_ADD_TO_CART'                               
       WHEN PRODUCT_ID =  product_id_ AND AVAIL_TO_SELL = 'YES' AND Enable_Add_To_Cart(PRODUCT_ID)='YES' AND SELL_ONLY_LINKED != 'YES' THEN '&ACTION_ADD_TO_CART' 
    END IF;   
ELSE '&ACTION_NO_ACTION'
END) ACTION2,

SQLPLUS中的错误

( begin case declare exit for goto if loop mod null pragma
raise return select update while with <an identifier>
<a double-quoted delimited-identifier> <a bind variable> <<
continue close current delete fetch lock insert open rollback
savepoint set sql execute commit forall merge pipe purge

（begin case declare exit for goto if loop mod null pragma
使用时升高返回选择更新
这是怎么回事？您可以使用
acc\u type\u id.='ENDU'
作为
条件的一部分来实现相同的结果

(CASE 
      WHEN acc_type_id_ = 'ENDU' AND PRODUCT_ID !=  product_id_ AND AVAIL_TO_SELL = 'YES' AND Enable_Add_To_Cart(PRODUCT_ID)='YES' AND PROD_ITEM_PKG.Get_Allow_Endu_Purch(PRODUCT_ID)='YES' THEN '&ACTION_ADD_TO_CART'                               
      WHEN acc_type_id_ = 'ENDU' AND PRODUCT_ID =  product_id_ AND AVAIL_TO_SELL = 'YES' AND Enable_Add_To_Cart(PRODUCT_ID)='YES' AND SELL_ONLY_LINKED != 'YES' AND PROD_ITEM_PKG.Get_Allow_Endu_Purch(PRODUCT_ID)='YES' THEN '&ACTION_ADD_TO_CART' 
      WHEN acc_type_id_ != 'ENDU' AND PRODUCT_ID !=  product_id_ AND AVAIL_TO_SELL = 'YES' AND Enable_Add_To_Cart(PRODUCT_ID)='YES' THEN '&ACTION_ADD_TO_CART'                               
      WHEN acc_type_id_ != 'ENDU' AND PRODUCT_ID =  product_id_ AND AVAIL_TO_SELL = 'YES' AND Enable_Add_To_Cart(PRODUCT_ID)='YES' AND SELL_ONLY_LINKED != 'YES' THEN '&ACTION_ADD_TO_CART' 
      ELSE '&ACTION_NO_ACTION'
END) ACTION2,

这是程序的一部分吗？