Writes information about a prepared statement to the SQL
    Descriptor Area (SQLDA).

    The DESCRIBE statement is a dynamic SQL statement. Dynamic SQL
    lets programs accept or generate SQL statements at run time,
    in contrast to SQL statements that are part of the source code
    for precompiled programs or SQL module language procedures.
    Unlike precompiled SQL or SQL module language statements, such
    dynamically executed SQL statements are not part of a program's
    source code but are generated while the program runs. Dynamic SQL
    is useful when you cannot predict the type of SQL statement your
    program needs to process.

    The SQLDA is a collection of host language variables used only
    in dynamic SQL programs. To use the SQLDA, host languages must
    support pointer variables that provide indirect access to storage
    by storing the address of data instead of directly storing data
    in the host language variable. The languages supported by the
    SQL precompiler that also support pointer variables are Ada, C,
    and PL/I. Any other language that supports pointer variables can
    use the SQLDA, but must call SQL module procedures that contain
    SQL statements instead of embedding the SQL statements directly
    in source code. The SQLDA provides information about dynamic SQL
    statements to the program and information about memory allocated
    by the program to SQL.

    The DESCRIBE statement is how SQL writes information that the
    program uses to the SQLDA. Specifically, the DESCRIBE statement
    stores in the SQLDA the number and data types of any select list
    items or parameter markers in a prepared statement.

    The Oracle Rdb SQL Reference Manual describes in more detail
    the specific fields of the SQLDA and how programs use it to
    communicate about select list items and parameter markers in
    prepared statements.