Host Variables in Embedded SQL

Host variables are C variables that are identified to the SQL preprocessor. Host variables can be used to send values to the database server or receive values from the database server.

Host variables are quite easy to use, but they have some restrictions. Dynamic SQL is a more general way of passing information to and from the database server using a structure known as the SQL Descriptor Area (SQLDA). The SQL preprocessor automatically generates a SQLDA for each statement in which host variables are used.

Host variables cannot be used in batches. Host variables cannot be used within a subquery in a SET statement.

• Host Variable Declaration
  Host variables are defined by putting them into a declaration section. According to the ANSI embedded SQL standard, host variables are defined by surrounding the normal C variable declarations with the following:
• C Host Variable Types
  Only a limited number of C data types are supported as host variables. Also, certain host variable types do not have a corresponding C type.
• Host Variable Usage
  Host variables can be used in the following circumstances:
• Indicator Variables
  Indicator variables are C variables that hold supplementary information when you are fetching or putting data. There are several distinct uses for indicator variables: