如何通过比较重复字符串来更新sql记录？

Question

我有一张下表：

id   |  echantillon_dta  |   Est_en_double 
1    |   Bonjour         |      null
2    |   Bonjour         |      null
3    |   Bonjour         |      null
4    |   Joke            |      null
5    |   Joke            |      null
6    |                   |      null 

处理后查询会显示如下：

id   |   echantillon_dta        |   Est_en_double 
1    |   Bonjour         |      1
2    |   Bonjour         |      1 
3    |   Bonjour         |      1 
4    |   Joke            |      4
5    |   Joke            |      4
6    |                   |      null 

如何比较字符串与字符串？以及如何像这样更新列？

Answer 1

当 Record_Details 相同时，您可以使用 min(id) 更新。

还有一个错误描述：
6 | Nope | 6 //No duplicates found, stay null
id 6 不重复但isDuplicate column 值是6，不应该是null吗？
所以我用having count(1) > 1 来解决它。

CREATE TABLE Table1
  ("id" int, "Record_Details" varchar2(11), "isDuplicate" varchar2(4))
;

INSERT ALL 
  INTO Table1 ("id", "Record_Details", "isDuplicate")
       VALUES (1, 'Hello World', NULL)
  INTO Table1 ("id", "Record_Details", "isDuplicate")
       VALUES (2, 'Hello World', NULL)
  INTO Table1 ("id", "Record_Details", "isDuplicate")
       VALUES (3, 'Hello World', NULL)
  INTO Table1 ("id", "Record_Details", "isDuplicate")
       VALUES (4, 'Joke', NULL)
  INTO Table1 ("id", "Record_Details", "isDuplicate")
       VALUES (5, 'Joke', NULL)
  INTO Table1 ("id", "Record_Details", "isDuplicate")
       VALUES (6, 'Nope', NULL)
SELECT * FROM dual
;

update (
  select T.*
     , (select min("id") 
        from Table1 Tmp 
        where Tmp."Record_Details" = T."Record_Details"
        group by Tmp."Record_Details" having count(1) > 1 --No duplicates found, stay null

     ) as "new_isDuplicate"
  from Table1 T
)
set "isDuplicate" = "new_isDuplicate"

6 行受影响

select * from Table1

编号 |记录_详情 |是重复的 -: | :------------- | :---------- 1 |你好世界 | 1 2 |你好世界 | 1 3 |你好世界 | 1 4 |笑话 | 4 5 |笑话 | 4 6 |没有 | 空

db小提琴here

Answer 2

您可以使用MERGE 语句和分析函数来查找重复项：

Oracle 设置：

CREATE TABLE Table_name ( id, Record_Details, isDuplicate ) AS
SELECT 1, 'Hello World', CAST( NULL AS NUMBER ) FROM DUAL UNION ALL
SELECT 2, 'Hello World', NULL FROM DUAL UNION ALL
SELECT 3, 'Hello World', NULL FROM DUAL UNION ALL
SELECT 4, 'Joke',        NULL FROM DUAL UNION ALL
SELECT 5, 'Joke',        NULL FROM DUAL UNION ALL
SELECT 6, 'Nope',        NULL FROM DUAL;

合并：

MERGE INTO table_name dst
USING (
  SELECT ROWID rid,
         MIN( id ) OVER ( PARTITION BY Record_details ) AS dupe_id
  FROM   table_name
) src
ON (
    dst.ROWID = src.RID
AND dst.id <> src.dupe_id -- remove this line if you want to update all rows
) 
WHEN MATCHED THEN
  UPDATE SET isDuplicate = dupe_id;

输出：

身份证 |记录详细信息 |复制 -: | :------------- | ----------: 1 |你好世界 | 空 2 |你好世界 | 1 3 |你好世界 | 1 4 |笑话 | 空 5 |笑话 | 4 6 |没有 | 空

db小提琴here

Answer 3

您似乎想要最小的id 和相同的record_details。

这应该可行：

select t.*,
       min(id) over (partition by record_details) as isDuplicate
from t;

如果您希望这是 update，关联子查询是一种简单的方法：

update t
    set isduplicate = (select min(t2.id)
                       from t t2
                       where t2.record_details = t.record_details
                      );