Question

请考虑以下表格： -

-----------------------------------------
  ID      TEACHER    SUBJECT     GRADE
-----------------------------------------
  1        Jack       Physics      8
  2        Paul       Chemistry    10
  3        Susan      English      6
  4        Jack       Maths        8
  5        Jack       Physics     10
  6        Paul       Chemistry   10

我想识别TEACHER和SUBJECT列具有相同值的行。与ID和GRADE列中的值无关。因此将识别以下行： -

 -------------------------------------
  ID      TEACHER     SUBJECT   GRADE
 -------------------------------------
  1        Jack       Physics      8
  2        Paul       Chemistry    10
  5        Jack       Physics     10
  6        Paul       Chemistry   10
 -------------------------------------

如何在oracle sql中实现这样的结果。

Answer 1

您可以使用以下选择：

SELECT 
      a.* 
  FROM (SELECT 
             COUNT(1) cnt,
             teacher,
             subject 
         FROM your_table
         GROUP BY teacher,subject
         HAVING COUNT(1) > 1)rec,
Your_table a
WHERE a.teacher=rec.teacher AND a.subject=rec.subject

Answer 2

SELECT * FROM table1 t1
WHERE EXISTS (
  SELECT null FROM Table1 t2
  WHERE t1."TEACHER" = t2."TEACHER"
    AND t1."SUBJECT" = t2."SUBJECT"
    AND t1."ID" <> t2."ID"
)
ORDER BY "ID"

演示：http://sqlfiddle.com/#!4/3d2bd4/3

Answer 3

使用ROW_NUMBER()将为教师和主题的独特组合提供一种简单的方法来选择一行，但我还没有完全匹配问题提供的结果。但是，使用ROW_NUMBER()启用一个逻辑，您可以在其中选择哪个（哪些）字段将确定返回哪些行：

SELECT 
       id, teacher, subject, grade 
FROM (
      SELECT
           id, teacher, subject, grade 
         , row_number() over(partition by teacher, subject ORDER BY id ASC) as RN
      FROM Table1
      )
WHERE rn = 1
ORDER BY teacher, subject ;

使用ID的升序结果为：

| ID | TEACHER |   SUBJECT | GRADE |
|----|---------|-----------|-------|
|  4 |    Jack |     Maths |     8 |
|  1 |    Jack |   Physics |     8 |
|  2 |    Paul | Chemistry |    10 |
|  3 |   Susan |   English |     6 |

或简单地将订单更改为：成绩DESC

| ID | TEACHER |   SUBJECT | GRADE |
|----|---------|-----------|-------|
|  4 |    Jack |     Maths |     8 |
|  5 |    Jack |   Physics |    10 |
|  2 |    Paul | Chemistry |    10 |
|  3 |   Susan |   English |     6 |

这种技术通常用于获取most recent或oldest行（基于某些日期/时间数据），以获取如何使用它的另一个示例。

SQLfiddle demo

根据ORACLE中的一组相同列查找行

3 个答案: