使用 Oracle 中同一行的值更新列
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Update a column using a value from the same row in Oracle
提问by Paul
I'm creating a SQL command in Oracle to update the value of "LOADDATE" to equal the value of "UPDATEDATE" on my table. What I have here works:
我正在 Oracle 中创建一个 SQL 命令来更新“LOADDATE”的值，使其等于我表上的“UPDATEDATE”的值。我在这里的作品：
BEGIN
UPDATE LOAD_SETTINGS
SET
LOADDATE = (
SELECT UPDATEDATE
FROM LOAD_SETTINGS
WHERE
MODEL = 'A001'
AND OBJECT = 'A'
)
WHERE
MODEL = 'A001'
AND OBJECT = 'A';
COMMIT;
END;
The one thing I know for sure about Oracle is that there is a lot that I do not know. Is there a better way to do this using any features of Oracle that I may not be familiar with? Perhaps without having to use a subquery? Or is this the the way to go?
关于 Oracle，我确定的一件事是，有很多我不知道的地方。有没有更好的方法来使用我可能不熟悉的 Oracle 的任何特性来做到这一点？也许不必使用子查询？或者这是要走的路？
Thanks!
谢谢！
回答by Conrad Frix
Since the where clause on the subquery is the same where on the outer there's no need for the subselect just reference the column directly
由于子查询上的 where 子句与外部的 where 子句相同，因此不需要子选择，只需直接引用列
UPDATE LOAD_SETTINGS
SET
LOADDATE = UPDATEDATE
WHERE
MODEL = 'A001'
AND OBJECT = 'A';
回答by Rajesh Kumar
UPDATE LOAD_SETTINGS
SET LOADDATE = UPDATEDATE
WHERE MODEL LIKE 'A001'
AND OBJECT LIKE 'A';
Since Modeland Objectare varchar it is good to use LIKEinstead of =.
由于Model和Object是VARCHAR是很好用LIKE的，而不是=。
