Question

INSERT INTO CUST_ID_HISTORY(CUST_ID,PREVIOUS_CUST_ID,UPDATE_DATE) 
SELECT CUST_ID,PREVIOUS_CUST_ID,UPDATE_DATE
FROM CUST_ID_HISTORY WHERE NOT EXISTS (SELECT 1 FROM CUST_ID_HISTORY WHERE
CUST_ID='SCB301' AND PREVIOUS_CUST_ID='SCB201');

以上查询在表中不存在插入值时向CUST_ID_HISTORY插入新记录。我遇到提供值的错误ORA-00001: unique constraint，但表中不存在这两个值。

Answer 1

您的语句从CUST_ID_HISTORY中选择并插入CUST_ID_HISTORY。换句话说，当CUST_ID != 'SCB301'和PREVIOUS_CUST_ID != 'SCB201'没有记录时，它会尝试为 CUST_ID_HISTORY 中的每条记录创建重复记录。据推测这是表的主键，因此ORA-00001唯一密钥违规。

如果你想要实现的是在CUST_ID_HISTORY中为这些值插入一条记录，那么你可能需要一个合并语句。像这样：

merge into CUST_ID_HISTORY tgt
using ( select 'SCB301' as id, 'SCB201' as prev_id
         from dual ) src
on ( src.id = tgt.cust_id 
      and src.prev_id = tgt.prev_cust_id)
when not matched then
    insert (cust_id, prev_cust_id, update_date)
    values (src.id, src.prev_id, sysdate)
/

Answer 2

查询：

INSERT INTO CUST_ID_HISTORY(CUST_ID,PREVIOUS_CUST_ID,UPDATE_DATE) 
SELECT CUST_ID,PREVIOUS_CUST_ID,UPDATE_DATE
FROM CUST_ID_HISTORY

将复制所有 CUST_ID_HISTORY表的行。

添加过滤器：

WHERE NOT EXISTS (
  SELECT 1
  FROM CUST_ID_HISTORY
  WHERE CUST_ID='SCB301' AND PREVIOUS_CUST_ID='SCB201'
);

如果行不存在，将检查表中是否存在CUST_ID='SCB301' AND PREVIOUS_CUST_ID='SCB201'的行，然后 all CUST_ID_HISTORY表中的行将被复制，如果如果存在这样的行，则该语句将插入零行。

因此，您的查询将复制所有行或不执行任何操作。

如果要插入一个新行，请检查它是否存在：

INSERT INTO CUST_ID_HISTORY(CUST_ID,PREVIOUS_CUST_ID,UPDATE_DATE) 
SELECT 'SCB301',
       'SCB201',
       SYSDATE   -- The current date/time
FROM   DUAL
WHERE NOT EXISTS (
  SELECT 1
  FROM CUST_ID_HISTORY
  WHERE CUST_ID='SCB301' AND PREVIOUS_CUST_ID='SCB201'
);

或：

MERGE INTO CUST_ID_HISTORY dst
USING (
  SELECT 'SCB301' AS CUST_ID,
         'SCB201' AS PREVIOUS_CUST_ID
  FROM   DUAL
) src
ON (   src.CUST_ID          = dst.CUST_ID
   AND src.PREVIOUS_CUST_ID = dst.PREVIOUS_CUST_ID )
WHEN NOT MATCHED THEN
  INSERT ( CUST_ID, PREVIOUS_CUST_ID, UPDATE_DATE ) 
  VALUES ( src.CUST_ID, src.PREVIOUS_CUST_ID, SYSDATE );

这将检查是否存在现有行，如果不存在则插入单行。

插入记录不存在的地方

2 个答案: