Joining virtual objects in Watson Query

To create a virtual view from existing virtualized tables, complete the following steps.

1. On the navigation menu, click Data > Data virtualization.
   The service menu opens to the Data sources page by default.
2. On the service menu, click Virtualization > Virtualized data.
   Your existing virtualized tables are listed.
3. Select two tables that you want to join and click Join to display the Join virtual objects window.
   Tip: If you prefer, you can click Open in SQL editor to skip the following steps and use the IBM common SQL engine instead. See the SQL Reference for more details on SQL syntax and function compatibility.
4. Use the graphical join wizard to select at least one join key, which consists of a pair of columns, of the same data type, from both of the virtualized tables. Then, from each table, select the columns to include in the join results. This step does not copy or move any data. It creates a table definition that is a combination of the two tables.
   
   To create a join key by using only the keyboard, follow these steps:

   1. Press Enter to select a column name in a row in Table 1.
   2. Press the Tab key to navigate to a column name in a row in Table 2.
   3. Press Enter on the row in Table 2. The rows are joined.

   Restrictions:

   • If you are joining tables with many rows, the preview of the join might time out after approximately 10 minutes if the data sources are unable to complete the processing of the join.
   • If the columns of the tables that you are joining do not share any common data, the preview of your join view might be empty. You can continue to join your virtual objects; however, the join view might not contain valuable data. Any data that you add to the virtual objects is automatically reflected in the join view.
   • You can join only two tables at one time. To join more than two tables, join two tables and get a view. Then, join the view and the third table to get another view.

   • Privileges and authorities that are granted to user groups are not considered when you create views. This limitation is a result of a Db2® limitation on groups.

     For more information, see Privileges and authorities that are granted to user groups are not considered when you create views.

5. Click Next. You can use the new table to query the data from both of the base tables.
6. On the Edit column names page, enter a View name, select a Schema, and edit column names as needed.
7. Select where to assign the view with one of the following options:

   Assign to	When to use this option
   Data request	Select Data request if you created the virtual table in response to a data request. Then, choose the appropriate request. The table also appears in Virtualized data.
   Project	Select Project if you created the virtual table to use in a specific project. Then, choose the appropriate project. The table also appears in Virtualized data.
   Virtualized data	Select Virtualized data if the table was not created in response to a data request or to use in a specific project. This setting is the default if no data requests or projects exist.

8. Click Create view to complete the process.