11.18. Virtuoso/PL Scrollable Cursors
Virtuoso/PL supports scrollable cursors, providing functionality similar to the ODBC scrollable cursor support. Scrollable Cursor support extends the basic (forward-only) syntax of DECLARE CURSOR and FETCH to support the various fetch directions & cursor modes. The Virtuoso/PL scrollable cursors always operate with a rowset size equal to 1. The keyset size (where applicable) is as per the default.
![[Note]](images/note.png)
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If a Virtuoso/PL cursor is declared forward only it supports only FETCH .. NEXT scroll direction. The FETCH defaults its direction to NEXT (if omitted) so this is how the syntax extensions to DECLARE CURSOR & FETCH interoperate with the forward-only cursors syntax. |
11.18.1. Declaring a Scrollable Cursor
Virtuoso/PL cursor types are specified at declaration time. Unlike the forward-only cursor declaration the scrollable cursor DECLARE CURSOR causes some actions (cursor statement preparation & cursor variable assignment). The cursor variable's value can not be copied, it should be passed only by reference in procedure calls. Scrollable cursors have an appropriate destructor, which will close the cursor when the cursor variable goes out of scope. Variables in the surrounding context are referenced similarly to the forward-only cursor.
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Some types of statements do not allow other cursor types than static. For example SELECT DISTINCT will always result in a static cursor, ignoring the cursor declared type. |