union with update

Question

Dear concern,

I have two tables table 1 = id, name, city
table 2 = id, name, city

I already combined all data of table 1 and table 2 and put them in table 3 (id,name,city) using UNION ALL

insert into table3
select *
from
( select * from dbo.table1
union all
select * from dbo.table2)t

now on regular base my table 1 and table 2 data update
so how I can put only the updated data from table 1 and table 2 to table 3

your help is really appreciable

thanks

Answer 1

Hi @Mohd. Omar Daraz ,

According to your requirement, you could consider to create triggers which could insert new data from table1, table2 to table3 antomatically.

Please refer below examples:

--create triggers on both tables  
CREATE TRIGGER Table1Insert ON table1  
FOR INSERT  
AS  
 INSERT INTO table3  
 select * FROM inserted  
  
 CREATE TRIGGER Table2Insert ON table2  
FOR INSERT  
AS  
 INSERT INTO table3  
 select * FROM inserted  

--insert some new data in table1 and table2  
insert into Table1 values  
  (555,'qqq','japan'),  
  (666,'www','china')  
      
  insert into Table2 values  
 (888,'ppp','london'),  
 (999,'ooo','france')  

--query table3  
 select * from table3  

Output:

id	name	city  
1	a	newyork  
2	b	washington  
3	c	dallas  
10	x	sydney  
20	y	melbourne  
30	z	queensland  
666	www	china  
555	qqq	japan  
999	ooo	france  
888	ppp	london  

Best regards
Melissa

---

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Answer 2

Hi @Mohd. Omar Daraz ,

Welcome to Microsoft Q&A!

For this type of problem we recommend that you post CREATE TABLE statements for your tables together with INSERT statements with sample data, enough to illustrate all angles of the problem. We also need to see the expected result of the sample.

I suppose that id will never updated in table1 and table2, you could refer below query and check whether it is working:

update a  
set a.city=b.city,a.name=b.name  
from table3 a    
inner join   
(select * from table1  
union  
select * from table2  
except  
select * from table3) b on a.id=b.id  

Best regards
Melissa

---

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Answer 3

Dear Melissa,

Thanks for your reply for better understanding

I have table 1 with column name- ID, name, City
value (1,'a','newyork')
value (2,'b','washington')
value (3,'c','dallas')
I have table 2 with column name- ID, name, City
value (10,'x','sydney')
value (20,'y','melbourne')
value (30,'z','queensland')

I did UNION ALL to both of these two table and put data to
table 3 with column name- ID, name, City
and value came
value (1,'a','newyork')
value (2,'b','washington')
value (3,'c','dallas')
value (10,'x','sydney')
value (20,'y','melbourne')
value (30,'z','queensland')

Now I update data to table 1 with column name- ID, name, City
value (555,'qqq','japan')
value (666,'www','china')

also I update data to table 2 with column name- ID, name, City
value (888,'ppp','london')
value (999,'ooo','france')

Now i want to see in table 3

           value (1,'a','newyork')
           value (2,'b','washington')
           value (3,'c','dallas')
           value (10,'x','sydney')
           value (20,'y','melbourne')
           value (30,'z','queensland')
           value (555,'qqq','japan')
           value (666,'www','china')
           value (888,'ppp','london')
           value (999,'ooo','france')

I hope this is not much more understandable and cleared

regards,

Answer 4

Hi @Mohd. Omar Daraz ,

Please refer below:

insert into  table3  
select * from table1  
union  
select * from table2  
except  
select * from table3  

Best regards
Melissa

---

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Answer 5

Hi @Mohd. Omar Daraz ,

EXCEPT returns distinct rows from the left input query that aren't output by the right input query.

select * from table1
union
select * from table2
except
select * from table3

So above whole part is combine all data from table 1 and table 2 and minus all the data from table3 in order to find out all updated part only.

For example, suppose (select * from table1 union select * from table2) as A and (select * from table3) as B. Then above query is A minus B which are the only updated data.

It is not load full data from table 1 and table 2 to table3 as you mentioned.

Please also refer my complete statement from below:

drop table if exists Table1,Table2,Table3  
  
create table Table1  
(  
id int,  
name varchar(20),  
city varchar(20)  
)  
  
insert into Table1 values  
(1,'a','newyork'),  
 (2,'b','washington'),  
(3,'c','dallas')  
  
create table Table2  
(  
id int,  
name varchar(20),  
city varchar(20)  
)  
  
insert into Table2 values  
(10,'x','sydney'),  
(20,'y','melbourne'),  
(30,'z','queensland')  
  
create table Table3  
(  
id int,  
name varchar(20),  
city varchar(20)  
)  
  
insert into table3  
select *  
from  
( select * from dbo.table1  
union all  
select * from dbo.table2)t  
  
insert into Table1 values  
 (555,'qqq','japan'),  
 (666,'www','china')  
  
 insert into Table2 values  
(888,'ppp','london'),  
(999,'ooo','france')  
  
--Method 1  
insert into table3  
select * from (  
(select * from table1  
union  
select * from table2)  
except  
select * from table3)a  
  
--Method 2  
 insert into  table3  
 select * from (  
 (select * from table1  
 except  
 select * from table3)   
 union  
 (select * from table2  
 except  
 select * from table3 ))a  
  
 --Method 3  
  insert into  table3  
 select * from table1  
 union  
 select * from table2  
 except  
 select * from table3  
  
select * from table3  

Output:

id name city  
1 a newyork  
2 b washington  
3 c dallas  
10 x sydney  
20 y melbourne  
30 z queensland  
555 qqq japan  
666 www china  
888 ppp london  
999 ooo france  

Best regards
Melissa

---

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