Question

I have 2 tables Test1 and Test1Update with following structure

Test1
id  name address

Test1Update 
id name address

here Test1 is old table and Test1Update is just replica of Test1 table
I want to a get records with this condition,

if(Test1.id=Test1Update.id){

select macthing values from Test1Update tables,and remaining unmatched values from Test1 table
}
else if(Test1.id!=Test1Update.id)
{
select * from Test1 only
}

As a example

Test1 has data like

Test1
id  name   address
1   john    Ca
2   mary    La

and Test1Update has data like

id  name  address
1   john  Las Vega

s

Now i want to get only matching records from Test1Update table and all unmatching records from

Test1 table so final output will be

 id  name  address
 1   john  Las Vegas
 2   mary    La

It means that old entry should be replced whenever there is any match
found with Test1Update.

How can I do that using a select query or by procedure?

Show me some way .

Answer 1

Assuming that all the id in Test1Update are present in Test1 that can be done simply with:

SELECT
  TEST1.ID,
  COALESCE(TEST1UPDATE.NAME, TEST1.NAME) as NAME,
  COALESCE(TEST1UPDATE.ADDRESS, TEST1.ADDRESS) as ADDRESS
FROM TEST1
LEFT JOIN TEST1UPDATE ON TEST1.ID = TEST1UPDATE.ID

See it work here: http://sqlfiddle.com/#!3/4a1f2/3/0

With the LEFT JOIN, if there is no matching entry in TEST1UPDATE, TEST1UPDATE.NAME and TEST1UPDATE.ADDRESS are null.
COALESCE gives you the first non null argument, so you’ve got the values from TEST1UPDATE if present, else from TEST1.

Edit for the UNION solution:

If there are a lot of fields, the COALESCE solution might be a bit verbose and you would like to use a UNION:

SELECT *
FROM TEST1UPDATE
INNER JOIN TEST1 ON TEST1.ID = TEST1UPDATE.ID

UNION

SELECT *
FROM TEST1
LEFT JOIN TEST1UPDATE ON TEST1.ID = TEST1UPDATE.ID
WHERE TEST1UPDATE.ID IS NULL;