SQL - Create view using sql command “UNION” from multiple tables

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i have 3 tables for example tb1,tb2,tb3 and each table include same data for different different company, so i want to get all 3 table data in a view when i do "union" its sowing duplicate data also. the reason is, not having same data in each column for duplicate rows. like below, can any one please help me. i want only one row from below
Note: emp_no is primary key
ex:-

emp_no   emp_name   emp_addr     emp_ph
101      abcd       xloc         000000 -- from tbl1
101      abcd       null         000000 -- from tbl2

Posted 27-Nov-15 22:10pm

Merajuddin Ansari

Updated 27-Nov-15 22:31pm

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Mehdi Gholam 28-Nov-15 4:20am

You probably need another column for the "company name" of the tb1-3 tables otherwise stands to reason you will get duplicate data.

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OriginalGriff · Accepted Answer · 2015-11-27T22:45:00

Basically, you shouldn't have different tables for different companies - you have have one table which contains a foreign key link to a separate table which just identifies the companies:
Companies

Id      Description
1       Joes Wheels
2       Mikes Tyres
3       Simons Hubs

DataTable:

Id      CompanyId  EmpNo   EmpName   ...
1       1          101     abcd
2       3          101     abcd
3       1          102     qwer
...

That way, you can identify "genuine" duplicates, and extract only the info you need for each company using JOIN and WHERE instead of UNION

This also makes it a lot more flexible to add a fourth company next week if you need to.