SQL Query Change and Optimization

We are a lead generation platform whose primary focus is to deliver quality sales contacts to its customers.
Guides and Brochures is powered by bespoke java software called Lead Engine. Lead Engine is written on the java MVC framework Grails. Essentially the code is written in groovy and java depending on the requirements.

Task Description
There is a function in the Lead Engine admin system whereby administrators can extract a set of data which contains the following fields:

• LEAD_ID
• Title
• First Name
• Last Name
• Email
• Categories
• Country of Residence

The current query is detailed below but does not return 1 row for each lead_id. It does however return a row for each category and lead_id.

Lead Engine uses a PostgreSQL 9.2 database to store and retrieve all its data.

Guides and Brochures will provide the developer with a database file containing a complete schema and some sample data.

1. The query should return records in as shorter time as possible with a maximum return time of around 20 seconds.
2. The query should return rows which are unique by lead_id and the categories field should contain a comma separated list of category abbreviations e.g “II,PROP,INV” for that unique lead_id.

Much more detail can be found in the attached PDF.
Many Thanks
Barry