References to SQL parameters and SQL variables

SQL parameters and SQL variables can be referenced anywhere in an SQL procedure statement where an expression or variable can be specified. Host variables cannot be specified in SQL functions, SQL procedures, or SQL triggers. SQL parameters can be referenced anywhere in the routine and can be qualified with the routine name. SQL variables can be referenced anywhere in the compound statement in which they are declared and can be qualified with the label name specified at the beginning of the compound statement.

All SQL parameters and SQL variables are considered nullable except SQL variables that are explicitly declared as NOT NULL. The name of an SQL parameter or SQL variable in an SQL routine can be the same as the name of a column in a table or view referenced in the routine. In this case, the name should be explicitly qualified to indicate whether it is a column, SQL variable, or SQL parameter.

If the name is not qualified, the following rules describe whether the name refers to the column or to the SQL variable or SQL parameter:

• If the tables and views specified in an SQL routine body exist at the time the routine is created, the name will first be checked as a column name. If not found as a column, it will then be checked as an SQL variable name in the compound statement, and then checked as an SQL parameter name.
• If the referenced tables or views do not exist at the time the routine is created, the name will first be checked as an SQL variable name in the compound statement and then as an SQL parameter name. If not found, it will be assumed to be a column.

The name of an SQL parameter or SQL variable in an SQL routine can be the same as the name of an identifier used in certain SQL statements. If the name is not qualified, the following rules describe whether the name refers to the identifier or to the SQL parameter or SQL variable:

• In the SET PATH and SET SCHEMA statements, the name is checked as an SQL parameter name or SQL variable name. If not found as an SQL variable or SQL parameter name, it will then be used as an identifier.
• In the CONNECT, DISCONNECT, RELEASE, and SET CONNECTION statements, the name is used as an identifier.