mybatis 动态 sql
mybatis 动态 sql <update id="updateAuthorIfNecessary"> update Author <set> <if test="username != null">username=#{username},</if> <if test="password != null">password=#{password},</if> <if test="email != null">email=#{email},</if> <if test="bio != null">bio=#{bio}</if> </set> where id=#{id} </update> http://mybatis.github.io/mybatis-3/zh/dynamic-sql.html