# Cross Table Sum Links columns in two tables. This column value is the sum of the values in a column in another table. This generator does not provide a preview. The sums are not computed until the other table is generated. For example, a **Customers** table contains a **Total\_Sales** column. The **Transactions** table uses a foreign key **Customer\_ID** column to identify the customer who made the transaction, and an **Amount** column that contains the amount of the sale. The **Customer\_ID** value in the **Transactions** table is a value from the **ID** primary key column in the **Customers** table. You assign the Cross Table Sum generator to the **Total\_Sales** column. In the generator configuration, you indicate that the value is the sum of the **Amount** values for the **Customer\_ID** value that matches the primary key **ID** value for the current row. For the **Customers** row for ID `123`, the **Total\_Sales** column contains the sum of the **Amount** column for **Transactions** rows where **Customer\_ID** is `123`. ## Characteristics


Consistency	No, cannot be made consistent.
Linking	No, cannot be linked.
Differential privacy	No
Data-free	No
Allowed for primary keys	No
Allowed for unique columns	No
Uses format-preserving encryption (FPE)	No
Privacy ranking	3
Generator ID (for the API)	`CrossTableAggregateGenerator`

## How to configure To configure the generator: 1. From the **Foreign Table** dropdown list, select the table that contains the column for which to sum the values. 2. From the **Foreign Key** dropdown list, select the foreign key.\ \ The foreign key identifies the row from the current table that is referred to in the foreign table. 3. From the **Sum Over** dropdown list, select the column for which to sum the values. 4. From the **Primary Key** dropdown list, select the primary key for the current table. 5. If [Structural data encryption](https://docs.tonic.ai/app/generation/generators-assign-config/generators-data-encryption-config) is enabled, then to use it for this column, in the advanced options section, toggle **Use data encryption process** to the on position.