oracle merge

--DROP TABLE PRODUCTS; 
--DROP TABLE NEWPRODUCTS; 
create table test_meger_PRODUCTS 
( 
PRODUCT_ID INTEGER, 
PRODUCT_NAME VARCHAR2(60), 
CATEGORY VARCHAR2(60) 
); 
insert into test_meger_PRODUCTS values (1501, ‘VIVITAR 35MM‘, ‘ELECTRNCS‘); 
insert into test_meger_PRODUCTS values (1502, ‘OLYMPUS IS50‘, ‘ELECTRNCS‘); 
insert into test_meger_PRODUCTS values (1600, ‘PLAY GYM‘, ‘TOYS‘); 
insert into test_meger_PRODUCTS values (1601, ‘LAMAZE‘, ‘TOYS‘); 
insert into test_meger_PRODUCTS values (1666, ‘HARRY POTTER‘, ‘DVD‘); 
commit; 
create table test_meger_NEWPRODUCTS 
( 
PRODUCT_ID INTEGER, 
PRODUCT_NAME VARCHAR2(60), 
CATEGORY VARCHAR2(60) 
); 
insert into test_meger_NEWPRODUCTS values (1502, ‘OLYMPUS CAMERA‘, ‘ELECTRNCS‘); 
insert into test_meger_NEWPRODUCTS values (1601, ‘LAMAZE‘, ‘TOYS‘); 
insert into test_meger_NEWPRODUCTS values (1666, ‘HARRY POTTER‘, ‘TOYS‘); 
insert into test_meger_NEWPRODUCTS values (1700, ‘WAIT INTERFACE‘, ‘BOOKS‘); 
commit; 

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select * from test_meger_products;
select * from test_meger_newproducts;

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merge into test_meger_products a using test_meger_newproducts b on (a.PRODUCT_ID = b.PRODUCT_ID )
when matched then
  update set a.product_name = b.product_name,a.category=b.category;

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merge into test_meger_products a
using test_meger_newproducts b
on (a.PRODUCT_ID = b.PRODUCT_ID)
when not matched then
    INSERT 
    (PRODUCT_ID 
    ,PRODUCT_NAME 
     ,CATEGORY) 
   VALUES 
    (b.PRODUCT_ID 
     ,b.PRODUCT_NAME 
    ,b.CATEGORY); 
select * from test_meger_products;
select * from test_meger_newproducts;

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merge into test_meger_products a
using (select count(*) co
         from test_meger_products b
        where b.PRODUCT_ID = 1501) c
    on (c.co <> 0 )
    when matched then
      update set a.product_name=‘update_1501‘ where a.product_id = ‘1501‘
    when not matched then
    insert  (PRODUCT_ID  ,PRODUCT_NAME  ,CATEGORY)   VALUES  (‘1501‘  ,‘insert-1‘  ,‘insert-2‘); 

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merge into test_meger_products a
using (select ‘1501‘ product_id, count(*) co
         from test_meger_products b
        where b.PRODUCT_ID = 1501) c
    on (a.product_id = c.product_id )
    when matched then
      update set a.product_name=‘update_15045‘
    when not matched then
    insert  (PRODUCT_ID  ,PRODUCT_NAME  ,CATEGORY)   VALUES  (‘1501‘  ,‘insert-1‘  ,‘insert-2‘);

=================================================================