Question

如果我有两个表格 TABLE1 AND TABLE2

TABLE1
DEPTNO  EMPID
10       1
10       2
10       3

TABLE2
EMPID   PRJNAME
1       ABC
1       DEF
3       XYZ

THE QUERY

SELECT T1.*,T2.PRJNAME FROM TABLE1 T1, TABLE2 T2 WHERE T1.EMPID = T2.EMPID;

将作为输出

DEPTNO  EMPID  PRJNAME
10       1      ABC
10       1      DEF
10       3      XYZ

如何修改QUERY以输出结果

DEPTNO  EMPID  PRJNAME
10       1      ABC
                DEF
         3      XYZ

Answer 1

首先，从不在from子句中使用逗号。始终使用正确的join语法。

其次，SQL结果集是无序集。您的结果集似乎假设了一个排序，但它没有order by。

我假设你打算：

select t1.*, t2.prjname
from table1 t1 join 
     table2 t2
     on t1.empid = T2.empid
order by t1.deptno, t1.empid, t2.prjname;

然后，您可以使用窗口函数执行您想要的操作：

select (case when lag(t1.deptno) over (partition by t1.deptno order by t1.empid, t2.prjname) is null
             then t1.deptno
        end) as deptno,
       (case when lag(t1.empid) over (partition by t1.deptno, t1.empid order by t2.prjname) is null
             then t1.empid
        end) as deptno,
       t2.prjname
from table1 t1 join 
     table2 t2
     on t1.empid = T2.empid
order by t1.deptno, t1.empid, t2.prjname;

Answer 2

select      case row_number () over (partition by t1.deptno          order by t1.empid,t2.prjname)  when 1 then t1.deptno end       as deptno
           ,case row_number () over (partition by t1.deptno,t1.empid order by t2.prjname)           when 1 then t1.empid  end       as empid
           ,t2.prjname

from                    table1 t1 

            join        table2 t2 

            on          t1.empid = t2.empid

order by    t1.deptno
           ,t1.empid
           ,t2.prjname
;

ORACLE - 分组部分输出

2 个答案: