Oracle：SQL根据同一表的另一行中的值更新同一表的行

Question

I need a sql to update the price column to 999 for the item records which meet the following condition:

1. The location of the ITEM should not be null for both the records.
2. Update the price to 999 for which one of the 2 records has location as null.

ID   LOCATION   ITEM   PRICE
1    NULL       101    0
2    123        101    0
3    NULL       102    0
4    NULL       102    0
5    124        103    0
6    NULL       103    0

OUTPUT TABLE SAMPLE

ID   LOCATION   ITEM   PRICE
1    NULL       101    999
2    123        101    0
3    NULL       102    0
4    NULL       102    0
5    124        103    0
6    NULL       103    999

Answer 1

Use IN (or EXISTS ) to check for the existence of a record with the item number where location is not null.

update items
set price = 999
where location is null
and item_id in (select item_id from items where location is not null);

Answer 2

I have created a table. Please find the query below. Just execute and check. You should get the desired result as per your ask.

CREATE TABLE TABLE1(ID INT, LOCATION INT, ITEM INT, PRICE INT)
INSERT INTO TABLE1 VALUES
(1, NULL, 101, 0), 
(2, 123 , 101, 0), 
(3, NULL, 102, 0), 
(4, NULL, 102, 0), 
(5, 124 , 103, 0), 
(6, NULL, 103, 0);

SELECT* FROM TABLE1;

WITH CTE AS
(
SELECT ITEM, COUNT(*) AS COUNTLOC FROM TABLE1 WHERE LOCATION IS NULL GROUP BY ITEM
)
UPDATE TABLE1
SET PRICE = 999 WHERE ITEM IN(SELECT ITEM FROM CTE WHERE COUNTLOC<2) AND LOCATION IS NULL;

Answer 3

update TABLE1 t1
INNER JOIN (select t12.item from TABLE1 t12 where t12.LOCATION is null
GROUP BY t12.ITEM 
HAVING count(t12.ITEM)=1)aaa on aaa.item = t1.ITEM
set t1.PRICE = 999 where t1.LOCATION is null