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<!DOCTYPE concept

  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

<concept id="GUID-2052461A-DF29-5DD0-A7D2-B46A50EAD762" xml:lang="en"><title>Cursor

navigation</title><shortdesc>Describes how the functionality of the rowset cursor and cursor

navigation.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>The rowset cursor can navigate to all available rows in the rowset. The

rows available depend on how the rowset is generated, and particularly on

whether the rowset is an SQL view using an evaluation window. </p>

<p>The cursor has two valid locations outside of the actual rowset, known

as the Beginning and the End. Initially and also following a reset, the cursor

is positioned at the beginning.</p>

<p>As regards navigating to next and previous rows, the beginning is considered

to lie immediately prior to the first row, and end is immediately following

the last row. Navigating to the first row is equivalent to navigating to the

next row from the beginning, which in an empty set takes the cursor to the

end of the set (maybe not immediately obvious). A similar process holds for

navigating to the last row of a set.</p>

<p>When updating or inserting a row, the cursor is in a special state which

prevents navigation until the update or insertion is completed.</p>

<p>The cursor may also end up in two other states</p>

<ul>

<li id="GUID-91DD7C42-E668-579D-B58D-2F45FDF61DDF"><p>after deletion of the

current row it is "in limbo" between the two neighbouring rows. Navigating

to next and previous will move to the respective row.</p> </li>

<li id="GUID-17BA2F54-A1FD-5796-AA2B-D59BF66CBBCD"><p>it may become invalid

after an error during navigation: either due to failure in the store or file

system, or due to loss of context when multiple rowsets are concurrently updating

a table. Navigating to any fixed position (i.e. not next or previous) will

restore the cursor.</p> </li>

</ul>

</conbody></concept>