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SQL Anywhere 17 » UltraLite - C++ Programming » Application development » UltraLite C++ application development using Embedded SQL

Host variables

Embedded SQL applications use host variables to communicate values to and from the database. Host variables are C variables that are identified to the SQL preprocessor in a declaration section.


In this section:
    Host variable declaration
    Define host variables by placing them within a declaration section. Host variables are declared by surrounding the normal C variable declarations with BEGIN DECLARE SECTION and END DECLARE SECTION statements.
    Data types
    To transfer information between a program and the database server, every data item must have a data type. You can create a host variable with any one of the supported types.
    Host variable usage in UltraLite C++
    Host variables can be used in the several specific circumstances.
    Host variable scope
    A host-variable declaration section can appear anywhere that C variables can normally be declared, including the parameter declaration section of a C function.
    Expressions as host variables
    Host variables must be simple names because the SQL preprocessor does not recognize pointer or reference expressions.
    Host variables in C++
    It is convenient to frequently declare your class in a separate header file.
    Indicator variables
    Indicator variables are C variables that hold supplementary information about a particular host variable. You can use a host variable when fetching or putting data. Use indicator variables to handle NULL values.