Oracle针对不同条件的订购 [英] Oracle order by for different conditions

问题描述

我有一个查询，我想根据条件做出两种订单.

I have a query and i would like to make two kinds of order based on a condition.

例如，如果一个字段为NULL，则我需要下一个命令，否则，我必须下一个命令.我该怎么办?

For example, if a field is NULL, i need to make an order and if it is not, i have to make another order. How i can do it ?

select *
  from table_1 t
  order by (if  t.field1 is null then
                   order by t.field2 DESC, field3 ASC
            else 
                  order by t.field4 ASC, field5 DESC)

这是一个示例代码:我想根据FIELD1的值进行不同的排序(ASC/DESC和不同的列)

This is a sample code: i want to make different order (ASC/DESC and different columns), based on the value of FIELD1

示例

有条件的

ID FIELD1  FIELD2  FIELD3  FIELD4  FIELD5
1   1       2       3       4       5
2   NULL    6       7       8       9

数据

ID PARENT_ID DATA1 DATA2 DATA3
1  1         X     Y     J
2  1         Z     W     U
3  2         XY    YX    O
4  2         ZW    WZ    I

select d.*
  from data d, conditional c
 where d.parent_id = c.id
   and d.parent_id = 1
order by
       case 
           when c.field1 is null then
              data1 asc, data2 desc
           else
              data3 asc, data1 desc
       end

在此示例中，我选择数据行ONE和第二行(父ID = 1的行). 现在，我已经做出了这个决定，我想基于CONDICTIONAL.FIELD1列的值来处理DATA列.我希望现在更干净.

In this example i select the DATA rows ONE and TWO (the rows that have parent id = 1). Now that i have make this decision, i want to orther the DATA columns based on the value of CONDICTIONAL.FIELD1 column. I hope now is more clean.

确保此查询确实有效，但这是我需要的".

Sure this query doesent work but this is "what i will need."

推荐答案

您可以在ORDER BY子句中使用CASE构造:

You can have CASE construct in the ORDER BY clause :

SQL> SELECT * FROM EMP T
  2  ORDER BY
  3  CASE
  4     WHEN COMM IS NULL
  5     THEN SAL
  6     ELSE EMPNO
  7  END
  8  /

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20
      7900 JAMES      CLERK           7698 03-DEC-81        950                    30
      7876 ADAMS      CLERK           7788 23-MAY-87       1100                    20
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      7839 KING       PRESIDENT            17-NOV-81       5000                    10
      7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300         30
      7521 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
      7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
      7844 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30

14 rows selected.

注意:照顾ORDER BY子句中列的DATA TYPE.

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