<?xml version="1.0" encoding="utf-8"?>

<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->

<!-- This component and the accompanying materials are made available under the terms of the License 

"Eclipse Public License v1.0" which accompanies this distribution, 

and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->

<!-- Initial Contributors:

    Nokia Corporation - initial contribution.

Contributors: 

-->

<!DOCTYPE concept

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

<concept xml:lang="en" id="GUID-47419CFB-163D-5A4E-8A00-C73773353BDF"><title>Column type characteristics</title><prolog><metadata><keywords/></metadata></prolog><conbody><p>DBMS has a rich set of column types. </p> <p>The Store database implementation supports all column types, and any column type can be nullable or marked as not-null.</p> <section><title>Fixed width columns</title> <p>All numeric and date/time columns are fixed width, though <codeph>Null</codeph> values will take no extra storage space in the database. See <xref href="GUID-4D96BFA5-3C4F-320F-BA9F-3511925A8137.dita"><apiname>TDbColType</apiname></xref> for the characteristics of fixed width column types.</p> </section> <section><title>Variable width columns</title> <p>Text and Binary columns are all variable length.</p> <p>The short column types <codeph>Text8</codeph>, <codeph>Text16</codeph> and <codeph>Binary</codeph> support the maximum length attribute, and can only store up to 255 units (characters or bytes) of data. If <codeph>KDbUndefinedLength</codeph> is specified as the maximum length attribute for these column types when a table is created, they are given a maximum length of 255.</p> <p>Long column types <codeph>LongText8</codeph>, <codeph>LongText16</codeph> and <codeph>LongBinary</codeph> can theoretically store up to 2GB of data depending on resources available in the store, at the cost of a little more storage overhead than short columns.</p> <p>A <codeph>Null</codeph> variable length column is one with no data in it, in particular DBMS does not distinguish between a zero-length Text column and a <codeph>Null</codeph> value Text column. See <xref href="GUID-4D96BFA5-3C4F-320F-BA9F-3511925A8137.dita"><apiname>TDbColType</apiname></xref> for the characteristics of the variable width column types.</p> <p>See also:</p> <ul><li id="GUID-4D82433D-E17F-5572-8054-6AE364616C54"><p><xref href="GUID-785B2F0B-E7E6-5DAE-98F1-6C32BED25964.dita">Database storage overhead</xref> </p> </li> </ul> </section> </conbody></concept>