SQL Reference

Null attributes of result columns

Result columns do not allow null values if they are derived from:

• A column that does not allow null values
• A constant
• The COUNT or COUNT_BIG function
• A host variable that does not have an indicator variable
• A scalar function or expression that does not include an operand that allows nulls.

Result columns allow null values if they are derived from:

• Any column function except COUNT or COUNT_BIG
• A column that allows null values
• A scalar function or expression that includes an operand that allows nulls
• A NULLIF function with arguments containing equal values.
• A host variable that has an indicator variable.
• A result of a set operation if at least one of the corresponding items in the select list is nullable.
• An arithmetic expression or view column that is derived from an arithmetic expression and the database is configured with DFT_SQLMATHWARN set to yes
• A dereference operation.

Names of result columns

• If the AS clause is specified, the name of the result column is the name specified on the AS clause.
• If the AS clause is not specified and the result column is derived from a column, then the result column name is the unqualified name of that column.
• If the AS clause is not specified and the result column is derived using a dereference operation, then the result column name is the unqualified name of the target column of the dereference operation.
• All other result column names are unnamed. ⁵²

⁵²

The system assigns temporary numbers (as character strings) to these columns.