Grouping data items using REDEFINES in COBOL embedded SQL applications

You can use the REDEFINES clause when declaring host variables. If you declare a member of a group data item with the REDEFINES clause, and that group data item is referred to as a whole in an SQL statement, any subordinate items containing the REDEFINES clause are not expanded.
For example: 
    01 foo1.                        
     10 a pic s9(4) comp-5.     
     10 a1 redefines a pic x(2).
     10 b pic x(10).
Referring to foo1 in an SQL statement as follows: 
    ... INTO :foo1 ...
This statement is equivalent to: 
    ... INTO :foo1.a, :foo1.b ...
That is, the subordinate item a1 that is declared with the REDEFINES clause, is not automatically expanded out in such situations. If a1 is unambiguous, you can explicitly refer to a subordinate with a REDEFINES clause in an SQL statement, as follows: 
    ... INTO :foo1.a1 ...
or 
    ... INTO :a1 ...