Fixing the ORA-00998 Error in a SQL View Creation

Introduction

The ORA-00998 error is encountered in SQL when attempting to create a view without specifying proper column aliases for expressions. This error occurs when the view definition contains expressions that are not assigned unique column names. To resolve this issue, you must explicitly provide column aliases for all expressions in the view definition.

00998 Error Explained

The ORA-00998 error message reads "must name this expression with a column alias". This error indicates that the SQL statement lacks column aliases for one or more expressions in the SELECT list or WHERE clause. Without proper column aliases, the database cannot identify each expression uniquely within the view.

Specifying Column Aliases

To fix the ORA-00998 error, you must modify the view definition to include column aliases for all expressions. A column alias is a temporary name assigned to an expression in a SQL statement. It allows you to refer to the expression using a specific name within the view.

Column aliases are specified using the AS keyword. For example, the following statement creates a view named "B" that includes two columns:

``` CREATE VIEW B AS SELECT Cprd_no AS Product_Number, Emp_no AS Employee_Number FROM Employee; ```

Resolving the Error

Once you have added column aliases to all expressions in the view definition, you should be able to create the view without encountering the ORA-00998 error. In the example provided in the original paragraph, the following statement would fix the issue:

``` CREATE VIEW B (Product_Number, Employee_Number) AS SELECT Cprd_no, Emp_no FROM Employee; ```