# Lookup The **Lookup** function finds matching data inside a workbook data element, either in the same table, or in an external table. All elements must be on the same data connection. ### Syntax ``` Lookup(formula, local key 1, external key 1, [local key 2], [external key 2], ...) ``` This function has the following arguments:
formulaRequired
The formula to compute (or the target column to reference) for the row in the target element.
local key 1Required
The column to use as a join key in the local data element.
external key 1Required
The column to use as a join key in the target data element.
local key 2Optional
The additional column to use as a join key in the local data element.
external key 2Optional
The additional column to use as a join key in the target data element.
### Examples ``` Lookup([Customers/Cust Name], [Cust Key], [Customers/Cust Key]) ``` Data is inserted into the *Sales* table’s **\[Calc]** column from the *Customer* table’s **\[Cust Name]** column. These two tables are joined using a single column (join key) from each table. In this case, both join keys are named **\[Cust Key]**. The function’s *formula* parameter directly references a column in the joined table. > ### 📘In formulas, reference columns from other tables with the **\[table name/]** prefix (e.g. **\[Customers/Cust Name]**).
``` Lookup([Customers/Zip Code], [Cust Name], [Customers/Name], [Cust Key], [Customers/Cust Key]) ``` Data is inserted into the *Ordered Items* table’s **\[Calc]** column from *Customer* table’s **\[Zip Code]** column. The function’s *formula* parameter directly references a column in the joined *Customers* table. These two tables are joined using two sets of join keys: * *Order Items’* **\[Cust Name]** column is joined with *Customer*’s **\[Name]** column; * *Order Items’* **\[Cust Key]** column is joined with *Customer*’s **\[Cust Key]** column
``` Lookup(Sum([Sales Amounts/Sales Amount]), [Order Number], [Sales Amounts/Order Number]) ``` Data is inserted into the *Orders* table’s **\[Calc]** column from *Sales Amount* table’s **\[Sales Amount]** column. The function’s *formula* parameter uses the Sum function to aggregate values from the *Sales Amount* table’s **\[Sales Amount]** column. These two tables are joined using a single set of join keys: *Orders’* **\[Order Number]** column is joined with *Sales Amounts’* **\[Order Name]** column.