UNION:the both tables should have same structure and datatype. the column

What are the differences between UNION and JOINS?

Question Posted / nikhila reddy

Answer Posted / nikhila reddy

UNION:the both tables should have same structure and datatype.
the column name will taken as first table ones it wont bother abt other tables.
example:
emp table as
eid ename esal
1 a 10k
2 b 20k

dept table as
deptid deptname deptsal
11 aa 20k
12 bb 50k

select * from emp
union
select * from dept

empid empname empsal
1 a 10k
2 b 20k
11 aa 20k
12 bb 50k

now u can observe col name taking alias of first table.
no need of relation between a tables.
it will remove duplicate records.

joins:it will join only required fields from different tables.
no need of same structure for tables..
it should have relation between a tables.

Is This Answer Correct ?

0 Yes

0 No

Post New Answer View All Answers

Please Help Members By Posting Answers For Below Questions

Do you know what are acid properties?

1018

What types of replication are supported in sql server?

997

We are updating a field in sql and alter the row also.after giving the commit command the system is crashed.what will happen to the commands given,whether it will update and alter the table or not?

1326

How can you transfer data from a text file to a database table? Or how can you export data from a table to a comma delimited (csv) file? Or how can you import data from ms access to a table in a database? Or how can you export data from a table to an excel file?

969

When setting replication, is it possible to have a publisher as 64 bit sql server and distributor or subscribers as a 32 bit sql server?

893

Where is localdb stored?

888

How to generate create table script on an existing table in ms sql server?

1091

What are different replication agents and what's their purpose? : sql server replication

958

What is the main difference between ‘between’ and ‘in’ condition operators?

1103

What is data block and how to define data block size?

977

What are “phantom rows”?

1608

What is the difference between composite index and covering index?

900

how you can move data or databases between servers and databases in sql server? : Sql server administration

915

What is microsoft sql server?

912

what do you understand by change data capture?

935