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<concept id="GUID-47419CFB-163D-5A4E-8A00-C73773353BDF" xml:lang="en"><title>Column
type characteristics</title><shortdesc>Describes fixed width and variable width columns.</shortdesc><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 id="GUID-5B7CB3CA-B531-4731-ACDF-80CE29A6EBE1"><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 id="GUID-4D860092-D42D-4301-8E06-D6D8D734AC91"><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>