Declare a cursor

You use the DECLARE statement to declare a cursor. This statement gives the cursor a name, specifies its use, and associates it with a statement. The following example is written in Informix® ESQL/C:

EXEC SQL DECLARE the_item CURSOR FOR
   SELECT order_num, item_num, stock_num
      INTO :o_num, :i_num, :s_num
      FROM items
   FOR READ ONLY;

The declaration gives the cursor a name (the_item in this case) and associates it with a SELECT statement. (Modify data through SQL programs discusses how a cursor can also be associated with an INSERT statement.)

The SELECT statement in this example contains an INTO clause. The INTO clause specifies which variables receive data. You can also use the FETCH statement to specify which variables receive data, as Locate the INTO clause discusses.

The DECLARE statement is not an active statement; it merely establishes the features of the cursor and allocates storage for it. You can use the cursor declared in the preceding example to read through the items table once. Cursors can be declared to read backward and forward (see Cursor input modes). This cursor, because it lacks a FOR UPDATE clause and because it is designated FOR READ ONLY, is used only to read data, not to modify it. Modify data through SQL programs covers the use of cursors to modify data.