What is a join?Explain the different types of joins?
Answer Posted / sandeep verma
Join match/combine two or more tables from a database. It means, combining rows or fields of two or more tables matching the common values. There are various types of joins which are as follows:
a) Self Join: joining table with it's own record to extract unique record (one employee is manager of other two employee)
b) Inner Join
i) Equi Join:No difference with inner join (just write join instead of inner join)
ii) Cross Join: will get you result each row of first table with each row of the other table(i.e. select * from employee cross join salary)
c) Outer Join
i) Left Outer Join:joins the matching records from two tables and all the records from left side of the table and those unmatched records have null value in right side of the table.
ii) Right Outer Join:joins the matching records from two tables and all the records from right side of the table and those unmatched records have null value in left side of the table.
iii) Full Outer Join: Regardless of matching record of both side of the tables, it produce all the records of both the table and produce NULL values for every column of the table that lacks of matching row.
Is This Answer Correct ? | 4 Yes | 0 No |
Post New Answer View All Answers
What operators deal with null?
Explian rowid, rownum? What are the psoducolumns we have?
how can we find the number of rows in a table using mysql? : Sql dba
How does rowid help in running a query faster?
GLOBAL TEMPORARY TABLE over Views in advantages insolving mutating error?
What is rank function in sql?
What is a join query?
How do I kill a query in postgresql?
Can we rollback delete command?
How to move files from one directory to another in pl sql?
Why do we use view in sql?
What will you get by the cursor attribute sql%found?
What are the differences between in and exists clause?
Can we delete column in sql?
What is full form of rtm?