| layout | element | title | language |
|---|---|---|---|
page |
notes |
Databases Week 2 - Joins, Nested Queries, and Database Structure |
Access |
Slides on Joins
###Basic Example
- Join main table to species table
- Show species and scientific name side by side
- Show distinct
- Filter by weight > 100 g
###What joins actually do
- Join species and plots tables
###Joins are part of the Query, not the database
- Save query
- Close query
- Open new query - shows no joins
###In Access they can be permanent - Relationships
- Save relationships
- Open new query - show joins
- Show that you can remove joins
Database Structure slides
Demonstrate by doing a query to get the number of trapping periods in each year.
- First GROUP BY yr and COUNT period
- Then GROUP BY yr and period
- Save that query
- Nest it to count the unique periods