Indicator variables are C variables that hold supplementary information when you are fetching or putting data. There are several distinct uses for indicator variables:
NULL values To enable applications to handle NULL values.
String truncation To enable applications to handle cases when fetched values must be truncated to fit into host variables.
Conversion errors To hold error information.
An indicator variable is a host variable of type a_sql_len that is placed immediately following a regular host variable in a SQL statement. For example, in the following INSERT statement, :ind_phone is an indicator variable:
EXEC SQL INSERT INTO Employees VALUES (:employee_number, :employee_name, :employee_initials, :employee_phone:ind_phone );
On a fetch or execute where no rows are received from the database server (such as when an error or end of result set occurs), then indicator values are unchanged.
To allow for the future use of 32 and 64-bit lengths and indicators, the use of short int for embedded SQL indicator variables is deprecated. Use a_sql_len instead.
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