Join vs Union

Question

Please tell me the difference between Join and Union?

Arjun Panwar · Answer

There are some Basic diff given below : Joine is bassically use for the columns but in case of union is does't. Union is bassically uses for the rows but in case of the Join is does't. A join selects columns from Two or more tables. A union selects rows.

Akash Ahlawat · Answer

Thanks

Satyapriya Nayak · Answer

Hi Akash, The JOIN keyword is used in an SQL statement to query data from two or more tables, based on a relationship between certain columns in these tables. The UNION operator is used to combine the result-set of two or more SELECT statements.The UNION operator selects only distinct values by default JOIN is used to retrive data from different tables using a single sql statement.union is used to combine the results of two or more sql querries. JOIN: ----- A Join is used for displaying columns with the same or different names from different tables. The output displayed will have all the columns shown individually. i.e. The columns will be aligned next to each other. UNION: ------ The UNION set operator is used for combining data from two tables which have columns with the same datatype. When a UNION is performed the data from both tables will be collected in a single column having the same datatype. For eg: See the two tables shown below: Table t1 Articleno article price manufacturer_id 1 hammer 3 $ 1 2 screwdriver 5 $ 2 Table t2 manufacturer_id manufacturer 1 ABC Gmbh 2 DEF Co KG Now for performing a JOIN type the query shown below SELECT articleno, article, manufacturer FROM t1 JOIN t2 ON (t1.manufacturer_id = t2.manufacturer_id); articelno article manufacturer 1 hammer ABC GmbH 2 screwdriver DEF Co KG That is a join. UNION means that you have to tables or resultset with the same amount and type of columns and you add this to tables/resultsets together. Look at this example: Table year2006 Articleno article price manufacturer_id 1 hammer 3 $ 1 2 screwdriver 5 $ 2 Table year2007 Articleno article price manufacturer_id 1 hammer 6 $ 3 2 screwdriver 7 $ 4 SELECT articleno, article, price, manufactruer_id FROM year2006 UNION SELECT articleno, article, price, manufacturer_id FROM year2007 articleno article price manufacturer_id 1 hammer 3 $ 1 2 screwdriver 5 $ 2 1 hammer 6 $ 3 2 screwdriver 7 $ 4 Thanks