Hibernate中的小写注释(Lowercase annotation in Hibernate)

 
 
 “我不认为这个问题要求薪水在失败和医疗之间。” 
 
 
 这个问题表明工资需要匹配一个特定的grade 。 
 
 
 
 “C的工资等级 
 
 
 当然，经典SCOTT / TIGER模式中的SALGRADE具有数字grade ： 
 
SQL> select * from salgrade;

     GRADE      LOSAL      HISAL
---------- ---------- ----------
         1        700       1200
         2       1201       1400
         3       1401       2000
         4       2001       3000
         5       3001       9999

SQL> 
 
 问题的不确定性与答案的奇异本质相吻合。 无论如何，正如我们所看到的，等级被分配到薪水带。 因此，为了找到特定年级的员工，我们需要将他们的薪水与该等级的上限和下限相匹配， losal和hisal 。 
 
 这是一个解决方案： 
 
SQL> select empno, ename, job, mgr
  2  from emp
  3       join dept
  4          on emp.deptno = dept.deptno
  5       join ( select * from salgrade
  6             where grade = 3 ) sg3
  7                     on emp.sal between sg3.losal and sg3.hisal
  8  where dept.dname IN ('SALES', 'RESEARCH')
  9  /

     EMPNO ENAME      JOB              MGR
---------- ---------- --------- ----------
      7499 ALLEN      SALESMAN        7698
      7844 TURNER     SALESMAN        7698

SQL>
 
 我更愿意保持连接条件与过滤器分开。 有几种方法可以做到这一点，查询演示了两种方法： 
 
 
 
 在内联视图中过滤表格 
 
 
 在主查询的WHERE子句中过滤表 
 
 
 语法允许我们在on子句中包含非连接条件，但这可能会产生副作用。 最好在连接和过滤器之间进行清晰的分离，这是ANSI 92语法的要点。 

 
 
" I don't think the question asked for salary to be between losal and hisal."
 
 
The question states the salary needs to match a specific grade.
 
 
 
" a salary grade of C.
 
 
Of course SALGRADE in the classic SCOTT/TIGER schema has a numeric grade:
 
SQL> select * from salgrade;

     GRADE      LOSAL      HISAL
---------- ---------- ----------
         1        700       1200
         2       1201       1400
         3       1401       2000
         4       2001       3000
         5       3001       9999

SQL> 
 
The sloppiness of the question fits the bizarre nature of the answer. Anyway, as we can see, the grades are allocated to salary bands. So to find the employees in a particular grade we need to match their salary to the upper and lower bounds of that grade, losal and hisal. 
 
Here is one solution: 
 
SQL> select empno, ename, job, mgr
  2  from emp
  3       join dept
  4          on emp.deptno = dept.deptno
  5       join ( select * from salgrade
  6             where grade = 3 ) sg3
  7                     on emp.sal between sg3.losal and sg3.hisal
  8  where dept.dname IN ('SALES', 'RESEARCH')
  9  /

     EMPNO ENAME      JOB              MGR
---------- ---------- --------- ----------
      7499 ALLEN      SALESMAN        7698
      7844 TURNER     SALESMAN        7698

SQL>
 
I prefer to keep join conditions separate from filters. There are a couple of ways of doing this, and the query demonstrates both:
 
 
 
Filter the table in an inline view
 
 
Filter the table in the main query's WHERE clause
 
 
The syntax allows us to include non-joining conditions in the on clause, but this can have side-effects. It's better to be clarity between joins and filters, which separation is the main point of the ANSI 92 syntax.