Why Use a Lookup | SharePoint Tutorial pdf

Why Use a Lookup?

Lookup and Choice column types serve similar purposes. Both provide choices from a list of values. With Choice columns, the values are entered directly in the column settings. With Lookup columns, the values come from another list.
Why go to the trouble of setting up a whole list just for a lookup? Because changes to the lookup list appear automatically in the lookup column.
To see how that works:
1. Select Charles Murphey as an assistant in the first row of the Phone List as shown in Figure, then then change his first name to Charley in the fifth row of the Phone List.
2. Click Actions -> Show in Standard View and “Charley Murphey” now appears in the first row.
3. Finally, click on Charley Murphey in the first and you’ll see his contact details.
Lookups link lists together!
In this case, you’ve got to enter assistants before you enter managers (otherwise, you won’t be able to find their assistant). That’s always true of lookups: the source list must contain the values you want to look up before you can fill out the destination list.
Lookups can be used across any list or library in the current site. For example, you might add a lookup column to a Task List that gets its values from a library containing Contracts. Each task then links to the contract that spells out the exact terms of the task as shown in Figure .
Figure : Using Lookup columns to drill down to a contract from a task list to a document