Help with create a trigger

Question

hello all
i have a 4 tables and i would like to create a trigger in a tables
CREATE TABLE CLIENT_INFO
( CLIENT_NO     VARCHAR2(10) CONSTRAINT CLIENT_INFO_CNO_PK PRIMARY KEY,
  CLIENT_NAME   VARCHAR2(50) NOT NULL,
  ORDERS_AMOUNT NUMBER(7)
CREATE TABLE STOCK_INFO
( ITEM_NO              VARCHAR2(10) ,
  ITEM_DESCRIPTION     VARCHAR2(100),
  SELLING_PRICE        NUMBER(6),
  QTY_IN_HAND          NUMBER(6)    NOT NULL,
  CONSTRAINT ITEM_NUM_SPRICE_PK PRIMARY KEY (ITEM_NO , SELLING_PRICE)
CREATE TABLE ORDER_INFO
( ORDER_NO     VARCHAR2(10) CONSTRAINT ORDER_INFO_ONO_PK PRIMARY KEY,
  CLIENT_NO    VARCHAR2(10),
  ORDER_DATE   DATE,
  ORDER_AMOUNT NUMBER(6),
  CONSTRAINT ORDER_INFO_CNO_FK  FOREIGN KEY (CLIENT_NO) REFERENCES CLIENT_INFO (CLIENT_NO)
CREATE TABLE ORDER_LINES
( ORDER_NO       VARCHAR2(10),
  ITEM_NO        VARCHAR2(10),
  LINE_QTY       NUMBER(6),
  SELLING_PRICE  NUMBER(6),
  TOTAL_PRICE    NUMBER(6)
ALTER TABLE ORDER_LINES
ADD  CONSTRAINT ORDER_LINES_ONO_FK FOREIGN KEY (ORDER_NO) REFERENCES ORDER_INFO (ORDER_NO);
ALTER TABLE ORDER_LINES
ADD  CONSTRAINT ORDER_LINES_INO_FK FOREIGN KEY (ITEM_NO) REFERENCES STOCK_INFO (ITEM_NO);i would like to create this trigger
1-order_amount in table 3 due to any (insert,update or delete ) in total_price in table 4
2-orders_amount in table 1 due to any (insert,update or delete ) in order_amount in table 3
i would like to ask another quotations r this relations in good for tables
thank's all

Answer 1

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plz i need a help to create a trigger
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Using a trigger won't solve your problem. You are trying to use child table triggers to maintain parent table information.
There is no transaction control to ensure that the parent table will be updated with the correct information.
One process could update child record 1 while another process is updating child record two. Each process will see a different total if they try to compute the sum of all child records since the first process will see the 'old' value for the child record that the second process is updating and the second process will the 'old' value for the child record that the first process is updating.
So the last process to commit could store the wrong total in the parent record withoug an exception ever being raised.
See Conflicting Writes in Read Committed Transactions in the Database Concepts doc
http://docs.oracle.com/cd/E14072_01/server.112/e10713/consist.htm
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some one ask me this quotation in interview
and im told him i can't understand this structure for database he said just do it
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And I would tell them that using a trigger is not the right way to accomplish that since it could invalidate the data concurrency and data consistency of the tables.
Sometimes you just have to tell people NO.