build.xml

<project default="query-to-property">
  
  <path id="hsql" >
    <pathelement location="lib/hsqldb-2.2.6.jar" />
  </path>
  
  <property name="db-driver" value="org.hsqldb.jdbc.JDBCDriver" />
  <property name="db-url" value="jdbc:hsqldb:mem:mydb" />
  
  <target name="fetch-hsqldb">
    <mkdir dir="lib" />
    <get src="http://repo1.maven.org/maven2/org/hsqldb/hsqldb/2.2.6/hsqldb-2.2.6.jar" dest="lib/" skipexisting="true" />
  </target>
  
  <target name="compile-tasks">
    <mkdir dir="build" />
    <javac srcdir="src" destdir="build" includeantruntime="true" />
  </target>
  
  <target name="setup-db" depends="fetch-hsqldb">
    <sql driver="${db-driver}" url="${db-url}" userid="" password="" classpathref="hsql">
      create table my_table (my_column VARCHAR(50));
      insert into my_table (my_column) values ('banana', 'apple');
    </sql>
  </target>
  
  <target name="query-to-property" depends="compile-tasks, setup-db">
    <taskdef name="resource-output-sql" classname="ResourceOutputSQLExec" classpath="build/" />
    
    <resource-output-sql driver="${db-driver}" url="${db-url}" userid="" password="" classpathref="hsql"
      print="true" showheaders="false" showtrailers="false" >
      <output>
        <propertyresource name="column-count" />
      </output>
      select count(my_column) from my_table;
    </resource-output-sql>
  
    <echo>The value of $${column-count} is ${column-count}</echo>
  </target>
  
</project>

ResourceOutputSQLExec.java

import org.apache.tools.ant.taskdefs.SQLExec;
import org.apache.tools.ant.types.Resource;

public class ResourceOutputSQLExec extends SQLExec {
    
    public Output createOutput() {
        return new Output();
    }
    
    public class Output {
        public void add(Resource output) {
            setOutput(output);
        }
    }
}