Union and Joins

Question

What is difference between Union and Joins? And where w use this in sql srver?

Raja T · Answer

Union: The UNION operator is used to combine the result-set of two or more SELECT statements. more details check out below links http://www.w3schools.com/sql/sql_union.asp http://www.codeproject.com/Articles/716224/SQL-Server-What-exactly-are-UNION-and-UNION-All https://www.mssqltips.com/sqlservertip/1387/union-vs-union-all-in-sql-server/ Join : In SQL joins are used to get data from two or more tables based on relationship between some of the columns in tables more details check below links http://www.aspdotnet-suresh.com/2011/12/different-types-of-joins-in-sql-server.html https://www.mssqltips.com/sqlservertip/1667/sql-server-join-example/ http://www.techonthenet.com/sql_server/joins.php Differences between JOIN and UNION 1. UNION combines the result set of two or more select queries into a single result set which includes all the rows from all the queries in the UNION where as JOIN retrieves data from two or more tables based on logical relationships between the tables. 2. In short UNION combines rows from 2 or more tables where JOIN combines columns from 2 or more tables.

Rajeesh Menoth · Answer

Hi joins combine data into new columns . If two tables are joined together then the data from the first table is shown in one set of column alongside the second table’s column in the same row. Unions combine data into new rows . If two tables are “unioned” together then the data from the first table is in one set of rows and the data from the second table in another set. The rows are in the same result. Reference : http://www.essentialsql.com/what-is-the-difference-between-a-join-and-a-union/ http://www.allinterview.com/showanswers/13863/what-is-the-difference-between-join-and-union.html

Rajeev Punhani · Answer

Hi Sandeep UNION combines the results of two or more queries into a single result set that includes all the rows that belong to all queries in the union. By using JOINs  you can retrieve data from two or more tables based on logical relationships between the tables. Joins indicate how SQL should use data from one table to select the rows in another table. If the above solution is helpful then accept the answer.

Nigel Fernandes · Answer

In simple terms: UNION combines rows from two or more tables JOIN Combines columns from two or more tables