I'm writing a query to select employee names from a database where the employees are married but have no children.

I have two different tables: Employee and Dependents

Employee has the following fields

```
fname, lname, ssn

```

And Dependents have the following fields

```
essn, dependents_name, relationship

```

Dependents.essn is a FK that references Employee.ssn

Some Employee.ssn have multiple tuples in Department, each with a different `relationship` status (spouse, son, daughter), describing the type of dependent that employee has. 

I'm looking to write a query that selects those employees, based on the ssn -> essn relationship, that have the relationship `spouse` but not the relationships `son` or `daughter`. 

So far, this is what I've tried:

```
select e.fname, d.relationship
from (employee e left outer join dependents d
on e.ssn = d.essn)
where d.relationship = 'spouse'

```

It returns the tuples of employees with the `spouse` value, but also with the `son` and `daughter` value.

How can I filter my tables to include only those employees with the `spouse` value?