Joins

Introduction

Starcounter supports inner joins, cross joins, left outer joins and right outer joins.

The default join type is inner join, so if you use the reserved word JOIN, the parser will interpret it as an inner join.

A cross join is an inner join without join condition, and thus can be regarded as a special case rather than a separate type of join.

This query is interpreted as a cross join:

SELECT e, d FROM Employee e JOIN Department d

It can also be written as an explicit cross join:

SELECT e, d FROM Employee e CROSS JOIN Department d

This query is interpreted as an inner join:

SELECT e, d FROM Employee e JOIN Department d ON e.Department = d

It can also be written as an explicit inner join:

SELECT e, d FROM Employee e INNER JOIN Department d ON e.Department = d

For left outer join and right outer join you may omit the reserved word OUTER.

This query returns all employees and their managers, including the employees that have no manager:

SELECT e1, e2 FROM Employee e1 LEFT JOIN Employee e2 ON e1.Manager = e2

This left outer join can also be written as a right outer join:

SELECT e1, e2 FROM Employee e2 RIGHT JOIN Employee e1 ON e1.Manager = e2

Last updated 7 years ago