java存儲過程和觸發(fā)器(24)-資料下載頁
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【正文】 d_id = 100 ? select * from s_ord where id = 100 169。 Dr. Philip Cannata Data Management 20 Java Triggers Think about what it would take to have triggers for update and delete of items. 169。 Dr. Philip Cannata Data Management 21 Java Triggers Why can’t we just do this? create or replace and pile java source named sgTriggerMethods as import .*。 import .*。 public class sgTriggerMethods{ public static void changeTotalForItemInsert(String ord_id, int price, int quan) throws SQLException { Connection conn = (jdbc:oracle:kprb:@)。 String query = update s_ord set total = (select sum(price * quantity) from s_item where ord_id = ?) where id = ? 。 PreparedStatement pstatement = (query)。 (1, ord_id)。 (2, ord_id)。 ()。 } } / 169。 Dr. Philip Cannata Data Management 22 Java Triggers To try out the trigger do the following: ? drop sg tables ? create sg tables ? recreate the trigger ? insert into s_item values(100,8,50536,125,1,null) 169。 Dr. Philip Cannata Data Management 23 Java Triggers The Dreaded Mutating Table Problem insert into s_item values(100,8,50536,125,1,null) * ERROR at line 1: ORA29532: Java call terminated by uncaught Java exception: : ORA04091: table is mutating, trigger/function may not see it ORA04088: error during execution of trigger 39?！?The problem is a trigger can’t make reference to the table being changed. String query = update s_ord set total = (select sum(price * quantity) from s_item where ord_id = ?) where id = ? 。 Problem! 169。 Dr. Philip Cannata Data Management 24 Java Stored Procedures Write some code
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