Oracle 11g Release 2

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create table TEST_FILE_MERGE
(
  customer_num    NUMBER,
  CUST_FIRST_NAME VARCHAR2(180),
  CUST_LAST_NAME  VARCHAR2(180),
  r_id            NVARCHAR2(1000)
  ,
  CONSTRAINT cumstom_unique UNIQUE (customer_num)
);
INSERT INTO TEST_FILE_MERGE VALUES( 123,'perter','foe','1')
1 rows affected

create table REQUEST
(
  req_id              NVARCHAR2(1000),
  cust_no             VARCHAR2(50),
  customer_first_name VARCHAR2(50),
  customer_last_name  VARCHAR2(50),
  error_code          NUMBER,
  "IS_CHECKED"          NUMBER
);
INSERT INTO REQUEST VALUES (1,123,'Peter','Foe',0,0)
1 rows affected

UPDATE (SELECT A.CUST_FIRST_NAME, A.CUST_LAST_NAME
,B.CUSTOMER_FIRST_NAME,B.CUSTOMER_LAST_NAME,B.ERROR_CODE,B.IS_CHECKED  
          FROM TEST_FILE_MERGE A
         INNER JOIN REQUEST B
            ON A.CUSTOMER_NUM = B.CUST_NO)
   SET CUSTOMER_FIRST_NAME  = CUST_FIRST_NAME,
       CUSTOMER_LAST_NAME   = CUST_LAST_NAME,
       ERROR_CODE           = 0,
       IS_CHECKED           = 1;
1 rows affected

SELECT * FROM REQUEST


REQ_ID
CUST_NO
CUSTOMER_FIRST_NAME
CUSTOMER_LAST_NAME
ERROR_CODE
IS_CHECKED


1
123
perter
foe
0
1