Multiple Database Implementation

Go Up to Using Strings or host-language Variables

To use a database specified by the user as a host-language variable in a CONNECT statement in multi-database programs, follow these steps:

1. Declare a database handle using the following SET DATABASE syntax:

   EXEC SQL
   SET DATABASE handle = COMPILETIME 'dbname';
   

   Here, <handle> is a hard-coded database handle supplied by the programmer, <dbname> is a quoted, hard-coded database name used by gpre during preprocessing.
2. Prompt the user for a database to open.
3. Store the database name entered by the user in a host-language variable.
4. Use the handle to open the database, associating the host-language variable with the handle using the following CONNECT syntax:

   EXEC SQL
   CONNECT :variable AS handle;
   

   The following C code illustrates these steps:

   . . .
   char fname[125];
   . . .
   EXEC SQL
   SET DATABASE DB1 = 'employee.ib';
   printf("Enter the desired database name, including node
   and path):\n");
   gets(fname);
   EXEC SQL
   CONNECT :fname AS DB1;
   . . .
   

In this example, SET DATABASE provides a hard-coded database file name for preprocessing with gpre. When a user runs the program, the database specified in the variable, fname, is used instead.