Creating Table Aliases

Aliases can make it easier to work with table names. Using aliases is helpful when:

• You want to make the statement in the SQL pane shorter and easier to read.
  
  
• You refer to the table name often in your query — such as in qualifying column names — and want to be sure you stay within a specific character-length limit for your query. (Some databases impose a maximum length for queries.)
  
  
• You are working with multiple instances of the same table (such as in a self-join) and need a way to refer to one instance or the other.

For example, you can create an alias "e" for a table name employee_information, and then refer to the table as "e" throughout the rest of the query.

You create table aliases in the SQL pane; you cannot create them in the Grid pane.

To create a table alias

1. Add the input sources to your query.
   
   
2. In the FROM clause in the SQL pane, add the alias name to each table you are creating an alias for. For example, to assign the alias "e" to the employee_information table and "p" to the positions table, you can create a FROM clause such as the following:

   FROM employee_information e, positions p
   

   Note   For most databases, you can add the option keyword AS between the table name and alias (for example, FROM employee_information AS e). However, some databases do not allow this keyword. For details, see Query Designer Considerations for Oracle Databases.

When you create a table alias, the Query Designer substitutes the alias for the corresponding table name in the Table column of the Grid pane.

Note   The SQL standard specifies that when you create an alias for a table name, you must use the alias to refer to the table in the rest of the SQL statement (that is, you cannot use the original table name). However, some databases do allow you to refer to the table by its original name. For details, refer to the documentation for your database.