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数据表数据#xff1a; mybatis类和查询语句#xff1a; 1. 当UserInfoMap中所有字段(包含association)都为NULL的话#xff0c;getUserInfo的返回结果是个null#xff0c;即使查询的记录存在#xff01;运行结果如下#xff1a;
2019-06-26 …先看一个示例
数据表数据 mybatis类和查询语句 1. 当UserInfoMap中所有字段(包含association)都为NULL的话getUserInfo的返回结果是个null即使查询的记录存在运行结果如下
2019-06-26 10:50:00.800 DEBUG 95032 --- [ main] com.zcm.mybatis.dao.UserDao.getUserInfo : Preparing: select name,phone,info_id from d_user where id ?
2019-06-26 10:50:00.854 DEBUG 95032 --- [ main] com.zcm.mybatis.dao.UserDao.getUserInfo : Parameters: 1(Integer)
2019-06-26 10:50:00.954 DEBUG 95032 --- [ main] c.z.m.d.m.InfoMapper.selectByPrimaryKey : Preparing: select id, card_id, birth, weight, height from d_info where id ?
2019-06-26 10:50:00.955 DEBUG 95032 --- [ main] c.z.m.d.m.InfoMapper.selectByPrimaryKey : Parameters: 0(Integer)
2019-06-26 10:50:00.956 DEBUG 95032 --- [ main] c.z.m.d.m.InfoMapper.selectByPrimaryKey : Total: 0
2019-06-26 10:50:00.957 DEBUG 95032 --- [ main] com.zcm.mybatis.dao.UserDao.getUserInfo : Total: 1
null
2. 当UserInfoMap中有字段不为NULL的时候getUserInfo返回的结果才不为null(前提查询的记录存在)如d_user表id1中为phone添加值x,如下图 这时再运行测试程序结果如下
2019-06-26 11:01:20.794 DEBUG 95861 --- [ main] com.zcm.mybatis.dao.UserDao.getUserInfo : Preparing: select name,phone,info_id from d_user where id ?
2019-06-26 11:01:20.856 DEBUG 95861 --- [ main] com.zcm.mybatis.dao.UserDao.getUserInfo : Parameters: 1(Integer)
2019-06-26 11:01:20.965 DEBUG 95861 --- [ main] c.z.m.d.m.InfoMapper.selectByPrimaryKey : Preparing: select id, card_id, birth, weight, height from d_info where id ?
2019-06-26 11:01:20.966 DEBUG 95861 --- [ main] c.z.m.d.m.InfoMapper.selectByPrimaryKey : Parameters: 0(Integer)
2019-06-26 11:01:20.967 DEBUG 95861 --- [ main] c.z.m.d.m.InfoMapper.selectByPrimaryKey : Total: 0
2019-06-26 11:01:20.968 DEBUG 95861 --- [ main] com.zcm.mybatis.dao.UserDao.getUserInfo : Total: 1
{phone:x}
所以综合本测试案例得出的最终结果是
1. 记录存在时不一定返回的对象一定不为null, 还要看查询的字段是否全部为NULL或者说是否有不为NULL的字段
2. 这个测试结果跟是否有关联查询无关!
