[Hibernate] inner Join和 left Join

@Test
    public void test11(){
        Session ss=HibernateUtil.getSession();
        //根据员工名称(SCOTT)找到和他所在的部门的其他员工的信息
        String hql=" select e from Emp e inner join e.dept";//下面一条等效
        //String hql="from Emp e inner join fetch e.dept";
        Query qr=ss.createQuery(hql);
        List<Emp> el =qr.list();
        System.out.println(el.size());
        for (Emp emp : el) {
            System.out.println(emp);
        }
        HibernateUtil.closeResource(ss);
    }
inner join代码

inner join输出27条结果,但是分块输出,条件查询也执行了几次.

Hibernate: 
    select
        emp0_.empno as empno1_1_,
        emp0_.ename as ename2_1_,
        emp0_.job as job3_1_,
        emp0_.mgr as mgr4_1_,
        emp0_.hiredate as hiredate5_1_,
        emp0_.sal as sal6_1_,
        emp0_.comm as comm7_1_,
        emp0_.deptno as deptno8_1_ 
    from
        EMP2 emp0_ 
    inner join
        DEPT2 dept1_ 
            on emp0_.deptno=dept1_.deptno
24
Hibernate: 
    select
        dept0_.deptno as deptno1_0_0_,
        dept0_.dname as dname2_0_0_,
        dept0_.loc as loc3_0_0_ 
    from
        DEPT2 dept0_ 
    where
        dept0_.deptno=?
Emp [empNo=7369, eName=SMITH, job=CLERK, mgr=7902, hireDate=1980-12-17 00:00:00.0, sal=800.0, comm=null, dept=Dept [deptNo=20, dName=RESEARCH, loc=DALLAS]]
Hibernate: 
    select
        dept0_.deptno as deptno1_0_0_,
        dept0_.dname as dname2_0_0_,
        dept0_.loc as loc3_0_0_ 
    from
        DEPT2 dept0_ 
    where
        dept0_.deptno=?
Emp [empNo=7499, eName=ALLEN, job=SALESMAN, mgr=7698, hireDate=1981-02-20 00:00:00.0, sal=1600.0, comm=300.0, dept=Dept [deptNo=30, dName=SALES, loc=CHICAGO]]
Emp [empNo=7521, eName=WARD, job=SALESMAN, mgr=7698, hireDate=1981-02-22 00:00:00.0, sal=1250.0, comm=500.0, dept=Dept [deptNo=30, dName=SALES, loc=CHICAGO]]
Emp [empNo=7566, eName=JONES, job=MANAGER, mgr=7839, hireDate=1981-04-02 00:00:00.0, sal=2975.0, comm=null, dept=Dept [deptNo=20, dName=RESEARCH, loc=DALLAS]]
Emp [empNo=7654, eName=MARTIN, job=SALESMAN, mgr=7698, hireDate=1981-09-28 00:00:00.0, sal=1250.0, comm=1400.0, dept=Dept [deptNo=30, dName=SALES, loc=CHICAGO]]
Emp [empNo=7698, eName=BLAKE, job=MANAGER, mgr=7839, hireDate=1981-05-01 00:00:00.0, sal=2850.0, comm=null, dept=Dept [deptNo=30, dName=SALES, loc=CHICAGO]]
Hibernate: 
    select
        dept0_.deptno as deptno1_0_0_,
        dept0_.dname as dname2_0_0_,
        dept0_.loc as loc3_0_0_ 
    from
        DEPT2 dept0_ 
    where
        dept0_.deptno=?
Emp [empNo=7782, eName=CLARK, job=MANAGER, mgr=7839, hireDate=1981-06-09 00:00:00.0, sal=2450.0, comm=null, dept=Dept [deptNo=10, dName=ACCOUNTING, loc=NEW YORK
]]
Emp [empNo=7788, eName=SCOTT, job=ANALYST, mgr=7566, hireDate=1987-04-19 00:00:00.0, sal=3000.0, comm=null, dept=Dept [deptNo=20, dName=RESEARCH, loc=DALLAS]]
Emp [empNo=7839, eName=KING, job=PRESIDENT, mgr=null, hireDate=1981-11-17 00:00:00.0, sal=5000.0, comm=null, dept=Dept [deptNo=10, dName=ACCOUNTING, loc=NEW YOR
K]]
Emp [empNo=7844, eName=TURNER, job=SALESMAN, mgr=7698, hireDate=1981-09-08 00:00:00.0, sal=1500.0, comm=0.0, dept=Dept [deptNo=30, dName=SALES, loc=CHICAGO]]
Emp [empNo=7876, eName=ADAMS, job=CLERK, mgr=7788, hireDate=1987-05-23 00:00:00.0, sal=1100.0, comm=null, dept=Dept [deptNo=20, dName=RESEARCH, loc=DALLAS]]
Emp [empNo=7900, eName=JAMES, job=CLERK, mgr=7698, hireDate=1981-12-03 00:00:00.0, sal=950.0, comm=null, dept=Dept [deptNo=30, dName=SALES, loc=CHICAGO]]
Emp [empNo=7902, eName=FORD, job=ANALYST, mgr=7566, hireDate=1981-12-03 00:00:00.0, sal=3000.0, comm=null, dept=Dept [deptNo=20, dName=RESEARCH, loc=DALLAS]]
Emp [empNo=7934, eName=MILLER, job=CLERK, mgr=7782, hireDate=1982-01-23 00:00:00.0, sal=1300.0, comm=null, dept=Dept [deptNo=10, dName=ACCOUNTING, loc=NEW YORK]
]
Hibernate: 
    select
        dept0_.deptno as deptno1_0_0_,
        dept0_.dname as dname2_0_0_,
        dept0_.loc as loc3_0_0_ 
    from
        DEPT2 dept0_ 
    where
        dept0_.deptno=?
Emp [empNo=67, eName=瑞士队, job=MANAGER, mgr=2018, hireDate=2018-06-21 21:37:53.0, sal=3000.0, comm=100.0, dept=Dept [deptNo=64, dName=WorldCup, loc=Moscow]]
Emp [empNo=19, eName=韩国队, job=MANAGER, mgr=7788, hireDate=2018-06-12 00:00:00.0, sal=3000.0, comm=100.0, dept=Dept [deptNo=20, dName=RESEARCH, loc=DALLAS]]
Hibernate: 
    select
        dept0_.deptno as deptno1_0_0_,
        dept0_.dname as dname2_0_0_,
        dept0_.loc as loc3_0_0_ 
    from
        DEPT2 dept0_ 
    where
        dept0_.deptno=?
Emp [empNo=13, eName=InverseT, job=TEST, mgr=7788, hireDate=2018-06-28 11:16:49.0, sal=1000.0, comm=100.0, dept=Dept [deptNo=86, dName=HBM, loc=Diego]]
Hibernate: 
    select
        dept0_.deptno as deptno1_0_0_,
        dept0_.dname as dname2_0_0_,
        dept0_.loc as loc3_0_0_ 
    from
        DEPT2 dept0_ 
    where
        dept0_.deptno=?
Emp [empNo=88, eName=Poly, job=Athlete, mgr=7788, hireDate=2018-06-28 10:21:47.0, sal=3000.0, comm=100.0, dept=Dept [deptNo=90, dName=FOOTBALL, loc=Seattle]]
Emp [empNo=89, eName=Odin, job=Athlete, mgr=7788, hireDate=2018-06-28 10:21:47.0, sal=3000.0, comm=100.0, dept=Dept [deptNo=90, dName=FOOTBALL, loc=Seattle]]
Hibernate: 
    select
        dept0_.deptno as deptno1_0_0_,
        dept0_.dname as dname2_0_0_,
        dept0_.loc as loc3_0_0_ 
    from
        DEPT2 dept0_ 
    where
        dept0_.deptno=?
Emp [empNo=83, eName=SET, job=主播, mgr=7788, hireDate=2018-06-28 10:08:45.0, sal=3000.0, comm=100.0, dept=Dept [deptNo=81, dName=BigDept, loc=NEWYORK]]
Emp [empNo=87, eName=InverseF, job=TEST, mgr=7788, hireDate=2018-06-28 10:18:08.0, sal=1000.0, comm=100.0, dept=Dept [deptNo=86, dName=HBM, loc=Diego]]
Hibernate: 
    select
        dept0_.deptno as deptno1_0_0_,
        dept0_.dname as dname2_0_0_,
        dept0_.loc as loc3_0_0_ 
    from
        DEPT2 dept0_ 
    where
        dept0_.deptno=?
Emp [empNo=16, eName=TOM, job=CODER, mgr=7788, hireDate=2018-06-28 11:18:18.0, sal=3000.0, comm=100.0, dept=Dept [deptNo=17, dName=VR, loc=Phoenix]]
Emp [empNo=63, eName=德国队, job=MANAGER, mgr=7788, hireDate=2018-06-21 21:24:37.0, sal=3000.0, comm=100.0, dept=Dept [deptNo=64, dName=WorldCup, loc=Moscow]]
Hibernate: 
    select
        dept0_.deptno as deptno1_0_0_,
        dept0_.dname as dname2_0_0_,
        dept0_.loc as loc3_0_0_ 
    from
        DEPT2 dept0_ 
    where
        dept0_.deptno=?
Emp [empNo=110, eName=Police, job=Police, mgr=110, hireDate=2001-09-09 09:46:40.0, sal=4000.0, comm=800.0, dept=Dept [deptNo=5, dName=DeptX, loc=null]]
inner Join输出结果
    //left join
    @Test
    public void test12(){
        Session ss=HibernateUtil.getSession();
        //根据员工名称(SCOTT)找到和他所在的部门的其他员工的信息
        //String hql="from Emp e left outer join e.dept on e.deptNo=e.dept.deptNo";//获取Emp+Dept的集合
        //String hql="select e from Emp e left outer join e.dept on e.deptNo=e.dept.deptNo";//获取Emp
        //以上两个个需要deptNo属性,在配置文件中配置property和Emp类中生成相应的getter setter
        String hql="from Emp e left outer join fetch e.dept ";//获取Emp
        Query qr=ss.createQuery(hql);
        
        List<Emp> el =qr.list();
        System.out.println(el.size());
        for (Emp emp : el) {
            System.out.println(emp);
        }
        HibernateUtil.closeResource(ss);
    }
left join
left join输出24条结果,因为3条是没有deptno的
Hibernate: 
    select
        emp0_.empno as empno1_1_0_,
        dept1_.deptno as deptno1_0_1_,
        emp0_.ename as ename2_1_0_,
        emp0_.job as job3_1_0_,
        emp0_.mgr as mgr4_1_0_,
        emp0_.hiredate as hiredate5_1_0_,
        emp0_.sal as sal6_1_0_,
        emp0_.comm as comm7_1_0_,
        emp0_.deptno as deptno8_1_0_,
        dept1_.dname as dname2_0_1_,
        dept1_.loc as loc3_0_1_ 
    from
        EMP2 emp0_ 
    left outer join
        DEPT2 dept1_ 
            on emp0_.deptno=dept1_.deptno
27
Emp [empNo=7934, eName=MILLER, job=CLERK, mgr=7782, hireDate=1982-01-23 00:00:00.0, sal=1300.0, comm=null, dept=Dept [deptNo=10, dName=ACCOUNTING, loc=NEW YORK]
]
Emp [empNo=7839, eName=KING, job=PRESIDENT, mgr=null, hireDate=1981-11-17 00:00:00.0, sal=5000.0, comm=null, dept=Dept [deptNo=10, dName=ACCOUNTING, loc=NEW YOR
K]]
Emp [empNo=7782, eName=CLARK, job=MANAGER, mgr=7839, hireDate=1981-06-09 00:00:00.0, sal=2450.0, comm=null, dept=Dept [deptNo=10, dName=ACCOUNTING, loc=NEW YORK
]]
Emp [empNo=19, eName=韩国队, job=MANAGER, mgr=7788, hireDate=2018-06-12 00:00:00.0, sal=3000.0, comm=100.0, dept=Dept [deptNo=20, dName=RESEARCH, loc=DALLAS]]
Emp [empNo=7902, eName=FORD, job=ANALYST, mgr=7566, hireDate=1981-12-03 00:00:00.0, sal=3000.0, comm=null, dept=Dept [deptNo=20, dName=RESEARCH, loc=DALLAS]]
Emp [empNo=7876, eName=ADAMS, job=CLERK, mgr=7788, hireDate=1987-05-23 00:00:00.0, sal=1100.0, comm=null, dept=Dept [deptNo=20, dName=RESEARCH, loc=DALLAS]]
Emp [empNo=7788, eName=SCOTT, job=ANALYST, mgr=7566, hireDate=1987-04-19 00:00:00.0, sal=3000.0, comm=null, dept=Dept [deptNo=20, dName=RESEARCH, loc=DALLAS]]
Emp [empNo=7566, eName=JONES, job=MANAGER, mgr=7839, hireDate=1981-04-02 00:00:00.0, sal=2975.0, comm=null, dept=Dept [deptNo=20, dName=RESEARCH, loc=DALLAS]]
Emp [empNo=7369, eName=SMITH, job=CLERK, mgr=7902, hireDate=1980-12-17 00:00:00.0, sal=800.0, comm=null, dept=Dept [deptNo=20, dName=RESEARCH, loc=DALLAS]]
Emp [empNo=7900, eName=JAMES, job=CLERK, mgr=7698, hireDate=1981-12-03 00:00:00.0, sal=950.0, comm=null, dept=Dept [deptNo=30, dName=SALES, loc=CHICAGO]]
Emp [empNo=7844, eName=TURNER, job=SALESMAN, mgr=7698, hireDate=1981-09-08 00:00:00.0, sal=1500.0, comm=0.0, dept=Dept [deptNo=30, dName=SALES, loc=CHICAGO]]
Emp [empNo=7698, eName=BLAKE, job=MANAGER, mgr=7839, hireDate=1981-05-01 00:00:00.0, sal=2850.0, comm=null, dept=Dept [deptNo=30, dName=SALES, loc=CHICAGO]]
Emp [empNo=7654, eName=MARTIN, job=SALESMAN, mgr=7698, hireDate=1981-09-28 00:00:00.0, sal=1250.0, comm=1400.0, dept=Dept [deptNo=30, dName=SALES, loc=CHICAGO]]
Emp [empNo=7521, eName=WARD, job=SALESMAN, mgr=7698, hireDate=1981-02-22 00:00:00.0, sal=1250.0, comm=500.0, dept=Dept [deptNo=30, dName=SALES, loc=CHICAGO]]
Emp [empNo=7499, eName=ALLEN, job=SALESMAN, mgr=7698, hireDate=1981-02-20 00:00:00.0, sal=1600.0, comm=300.0, dept=Dept [deptNo=30, dName=SALES, loc=CHICAGO]]
Emp [empNo=110, eName=Police, job=Police, mgr=110, hireDate=2001-09-09 09:46:40.0, sal=4000.0, comm=800.0, dept=Dept [deptNo=5, dName=DeptX, loc=null]]
Emp [empNo=89, eName=Odin, job=Athlete, mgr=7788, hireDate=2018-06-28 10:21:47.0, sal=3000.0, comm=100.0, dept=Dept [deptNo=90, dName=FOOTBALL, loc=Seattle]]
Emp [empNo=88, eName=Poly, job=Athlete, mgr=7788, hireDate=2018-06-28 10:21:47.0, sal=3000.0, comm=100.0, dept=Dept [deptNo=90, dName=FOOTBALL, loc=Seattle]]
Emp [empNo=87, eName=InverseF, job=TEST, mgr=7788, hireDate=2018-06-28 10:18:08.0, sal=1000.0, comm=100.0, dept=Dept [deptNo=86, dName=HBM, loc=Diego]]
Emp [empNo=13, eName=InverseT, job=TEST, mgr=7788, hireDate=2018-06-28 11:16:49.0, sal=1000.0, comm=100.0, dept=Dept [deptNo=86, dName=HBM, loc=Diego]]
Emp [empNo=63, eName=德国队, job=MANAGER, mgr=7788, hireDate=2018-06-21 21:24:37.0, sal=3000.0, comm=100.0, dept=Dept [deptNo=64, dName=WorldCup, loc=Moscow]]
Emp [empNo=67, eName=瑞士队, job=MANAGER, mgr=2018, hireDate=2018-06-21 21:37:53.0, sal=3000.0, comm=100.0, dept=Dept [deptNo=64, dName=WorldCup, loc=Moscow]]
Emp [empNo=83, eName=SET, job=主播, mgr=7788, hireDate=2018-06-28 10:08:45.0, sal=3000.0, comm=100.0, dept=Dept [deptNo=81, dName=BigDept, loc=NEWYORK]]
Emp [empNo=16, eName=TOM, job=CODER, mgr=7788, hireDate=2018-06-28 11:18:18.0, sal=3000.0, comm=100.0, dept=Dept [deptNo=17, dName=VR, loc=Phoenix]]
Emp [empNo=18, eName=吴奇隆, job=ACTOR, mgr=7788, hireDate=2018-06-20 00:00:00.0, sal=4000.0, comm=1000.0, dept=null]
Emp [empNo=11, eName=JASON, job=CODER, mgr=7788, hireDate=2018-06-28 11:14:47.0, sal=3000.0, comm=100.0, dept=null]
Emp [empNo=5, eName=YaoMing, job=Athlete, mgr=7788, hireDate=2018-06-28 11:08:59.0, sal=3000.0, comm=100.0, dept=null]
left join 输出结果
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原文地址：https://www.cnblogs.com/zienzir/p/9238393.html