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xbatis 一款非常好用 ORM 框架，它是如何多表 join 查询的？

日期：2025-02-19点击：70收藏

联表查询

内联查询

java

public class Demo {
    @Autowired
    private SysUserMapper sysUserMapper;

    public void page() {
        Pager<SysUser> pager= QueryChain.of(sysUserMapper)
                .join(SysUser::getRoleId, SysRole::getId)
                .like(SysUser::getUserName,"abc")
                .paging(Pager.of(1));
    }
}

左联查询

左联查询适合1对1情况，如果不是，则分页时需要关闭框架优化：Pager.of(1).setOptimize(false)

java

public class Demo {
    @Autowired
    private SysUserMapper sysUserMapper;

    public void page() {
        Pager<SysUser> pager= QueryChain.of(sysUserMapper)
                .leftJoin(SSysUser::getRoleId, SysRole::getId)
                .like(SysUser::getUserName,"abc")
                .paging(Pager.of(1));
    }
}

右联查询

java

public class Demo {
    @Autowired
    private SysUserMapper sysUserMapper;

    public void page() {
        Pager<SysUser> pager= QueryChain.of(sysUserMapper)
                .join(JoinMode.RIGHT, SysUser::getRoleId, SysRole::getId)
                .like(SysUser::getUserName,"abc")
                .paging(Pager.of(1));
    }
}

全连接查询

java

public class Demo {
    @Autowired
    private SysUserMapper sysUserMapper;

    public void page() {
        Pager<SysUser> pager= QueryChain.of(sysUserMapper)
                .join(JoinMode.FULL, SysUser::getRoleId, SysRole::getId)
                .like(SysUser::getUserName,"abc")
                .paging(Pager.of(1));
    }
}