define minimum length column in xsd

i am trying to generate an xsd based on a database created in vs.net 2008. How can i specify the minimum length for a column in my xsd? i want to be able t开发者_开发问答o do this in vs.net

<xsd:restriction base='xsd:string'>
   <xsd:minLength value='0'/>
   <xsd:maxLength value='50'/>
  </xsd:restriction>

Use restrictions:

<xs:restriction base="xs:integer">
      <xs:minInclusive value="0"/>
      <xs:maxInclusive value="100"/>
</xs:restriction>