Can you join a table to itself in SQL?

A self join allows you to join a table to itself. It helps query hierarchical data or compare rows within the same table. A self join uses the inner join or left join clause.

How do I join two tables in Db2?

  1. Inner join. You can use an inner join in a SELECT statement to retrieve only the rows that satisfy the join conditions on every specified table.
  2. Left outer join. The LEFT OUTER JOIN clause lists rows from the left table even if there are no matching rows on right table.
  3. Right outer join.
  4. Full outer join.

Is self join Inner join or outer join?

A self join can be an inner join (most joins are inner joins and most self joins are inner joins).

Can I join a table to itself?

You can join different tables by their common columns using the JOIN keyword. It is also possible to join a table to itself, which is known as a self join.

What is SQL Self join?

The SQL SELF JOIN is used to join a table to itself as if the table were two tables; temporarily renaming at least one table in the SQL statement.

Can you join on an alias SQL?

SQL aliases are custom names that you can give to the columns and tables you include in your queries. Aliases are very useful, as they can greatly improve the readability and maintainability of your query.

How use self join in DB2?

A self-join is a join of a table to itself. This table appears twice in the FROM clause and is followed by table aliases that qualify column names in the join condition. To perform a self-join, Db2 Database combines and returns rows of the table that satisfy the join condition.

What is an alias in DB2?

An alias is a substitute for the three-part name of a table or view. An alias can be defined at a local server and can refer to a table or view that is at the current server or a remote server. The alias name can be used wherever the table name or view name can be used to refer to the table or view in an SQL statement.

Where do we use self join?

You use a self join when a table references data in itself. E.g., an Employee table may have a SupervisorID column that points to the employee that is the boss of the current employee.

How does self join work in SQL?

A SQL self join joins data from the same table. In other words, it joins a table with itself. Records taken from the table are matched to other records from the same table.