<if test="recommend != null and recommend == true">
and g.recommend = 1
</if>
<if test="recommend != null and recommend == false">
and g.recommend = 0
</if>
recommend类型是bit类型，判断时只能用0（代表false）或者1 (true)
原文：https://www.cnblogs.com/hjy2018/p/9734936.html