Unit Eight: Joining Tables In this unit… ► Review ► Intro to Joining Tables ► Relational Records  In Joins  In Relates ► Joining Tables

Unit Eight – Joining Tables 2 Review Besides being a powerful part of Feature Data that allows us to create dynamic maps, the relationship between map features and attribute data is also the key to making our own data usable in a GIS.

Unit Eight – Joining Tables 3 Introduction to Joining ► We all use data, even if it is just a mailing list. ► Many data seem to have no geospatial component. ► But: Think of what is contained in a spreadsheet data file of fresh water sampling stations:  water quality information  a station number or station name  no discernable geo-spatial information What if we want to map these data?

Unit Eight – Joining Tables 4 Introduction to Joining An Excel table; a collection of data taken at sampling stations over time. An attribute table; points taken with a GPS at each of the ten sample stations. ► These two tables contain all the information needed to map the sampling profiles  across the sample area and  across time (note the sample date field) The information in this example is linkable by the station number: called “Station_No” in one file, and “ID” in the other.

Unit Eight – Joining Tables 5 Join Relationships Join matches up values in a single column of one table with the same values in a single column of a second. All other columns of the Join Table are “virtually” added to the Target Table.  You have the option to keep all records…  Or keep only matching records Keep all Keep only matching

Unit Eight – Joining Tables Join and Relate Relationships But it gets more complicated.. Relationships between data can be such that there is one instance of a value that matches to only one other instance of a value… or many to one - which is fine… But if there are one to many or even many to many, then join does not really do the job. For those cases, we use a “Relate”. ??

Unit Eight – Joining Tables ?? Relate Relationships In a Relate: 1. No “virtual join” occurs which would make records appear to be part of another record 2. Related records remain in their respective tables 3. What it does: Selection of a record in the parent table also selects any number of related records in related tables. (Relates are not covered in this workshop) You can Relate tables when you have either One-to-ManyOne-to-Manyor Many-to-ManyMany-to-Manyor Many-to-OneMany-to-One

Unit Eight – Joining Tables 8 Joining Tables ► Know the data! ► Identify fields in two tables that have a meaningful relationship ► Confirm with documentation or other metadata Our task: The names of Conservation parcels ???? ??

Unit Eight – Joining Tables 9 Joining Tables Then, the Join: 1. Layer context menu 2. J OINS & R ELATES >> J OIN… The layer selected from the TOC is the ‘Target’ The table selected in ‘2.’ is the ‘Source Table’ Only the fields of compatible data type are offered Our task: The names of Conservation parcels

Unit Eight – Joining Tables 10 Joining Tables 1. Prefix added from respective tables 2. Both match fields included 3. Name field (our goal) available for labeling, “Unique Value” Legend, further processing 4. Tons of other data as well, including new fields to Join more tables to…! Join shows all fields from both tables - with prefix Results: Tons of data this way

Unit Eight – Joining Tables 11 Your Turn… Chapter 8: Step 1 through END