Equi Join

In this lesson we are going to study about Equi joins in a database.
Equi Join or Theta Join: 
  • An Equi Join is a type of joins the tables based on the columns in two table with same values.
  • In Equi join ,the join condition must have an Equility operator.
  • Using other comparison operators (such as <) disqualifies a join as an equi-join.
Example: In the below diagram we are having two Table,Table:A and Table:B. In Table:A we are having five records and Table:B is having four
 records which is also in Table:A  if  we do the Equi join on Table:A column X with Table:B column Y,
 this will retrun the record which are common in both the table A column X and Table:B column Y .
NOTE:   The columns X of Table A and columns Y of Table B Datatype must be same and the resulting table is having all the columns of Table:A ,and Table:B.

Syntex:


Explicit Equi join:

SELECT *
FROM Table1
JOIN Table2 ON  Table1.columnX=  Table2. columnY ;

Implicit Equi join:

SELECT * FROM  Table1 ,  Table2  WHERE  Table1.columnX=  Table2. columnY ;

just have a look on below video and try to Cross Join table by your self and you can download the sql scrpit used in this video from here DOWNLOAD LINK


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