mybatis判断是否为空或null
<if test="catagoryCode != null and catagoryCode != ''">
AND train.CATAGORY_CODE = #{catagoryCode,jdbcType=VARCHAR}
</if>
<if test="catagoryCode != null and catagoryCode != ''">
AND train.CATAGORY_CODE = #{catagoryCode,jdbcType=VARCHAR}
</if>