# Example: List of City Trees

We have two Excel spreadsheets of city-planted trees.  We will attempt to find days when the same species of tree was planted in both of our lists. 

Our **strategy** for doing this will be to set *date* as a key column and then remove all of the other columns using the rules button.

We are going to choose a key column and also, choose some columns to ignore or delete.    

* First, make the view wider: `view->overAndUnderLayout`
* You can choose one or more key columns from`rulesButton->columns`Choose date in this example.
* Still at `rulesButton->columns->edit`do a delete of many unimportant columns.  Don't worry, the original file will be unharmed.  Keep deleting until all that remains is your Address\[key] column and a few other columns of interest.

![How the file looks when it first opens.  It has 17 columns.  We want to only look at two. Rightclick the column top you want to be your unique key.  Then in RulesButton->Columns start doing 'remove' on the unwanted columns.](https://1446155253-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LXUX-uoaZJ8T4qyEc-x%2F-LYTSCfdQRlNL1oRvKk9%2F-LYTWazGyNm33fxCR710%2Feverytree.png?alt=media\&token=5bbc696a-13d8-4fcf-a067-167adb14edc3)

![How NOT to choose a key: Springfield is an example of a bad key.  It is far from unique](https://1446155253-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LXUX-uoaZJ8T4qyEc-x%2F-LYTSCfdQRlNL1oRvKk9%2F-LYTVwlnXF3ZmwcG4S-0%2FbadKey.png?alt=media\&token=6dcf4a9d-d1c3-4d06-91b7-099da475c029)

![This is from: Session->SessionSettings->Columns    Keep rightclicking and removing until only your interesting columns remain. Note that each row here is a 'column' in your spreadsheet.](https://1446155253-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LXUX-uoaZJ8T4qyEc-x%2F-LYTcyLskILLjgcVaD_S%2F-LYTd320-RbAX7L1YLWW%2FREMovedSome.png?alt=media\&token=f1975a05-4db4-4155-8c4a-d0407fbd6866)

![Result: Using date as the key, we found a day when both lists planted the same species, a Magnolia, one August 21st.](https://1446155253-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LXUX-uoaZJ8T4qyEc-x%2F-LYTk0BMMS9fcfbX6Wtd%2F-LYTk3R3CzeCK5Keg4K-%2Fmagnolia.png?alt=media\&token=b4b467d7-10f9-4da2-b25a-71c950be1e4d)

Note that Beyond Compare is in Read-Only mode for Microsoft files (Excel & word) and PDF files.  We cannot alter the file nor save our work.  We can export the report though!  Use `Session->TableCompareReport`.