Insert values into empty column from another table-CodePudding

I work in SQL Developer by Oracle. I want attach dates from table 2 into empty column Date in Table 1 only into existed rows/ids. I tried to do it by below code but it doesn't work. It seems easy, but I couldnt find solution.

Table 1                Table 2
ID   Date              ID   Date
33   (null)            33   2021-01-02
22   (null)            22   2019-01-02
100  (null)            100  1999-09-09
200  (null)            200  2005-06-07
44   (null)            44   2010-02-02
                       999  2009-08-06

insert into table1 (date)
select
t2.date
from table2 t2 where table1.id in (select t2.id from table2);

CodePudding user response：

You want an update statement for existing rows. I’ll assume you haven’t really named your column date.

Something like:

Update table1 t1
Set t1.date_col = (select t2.date_col from table2 t2 where t1.id = t2.id)

CodePudding user response：

think you might be looking for the Oracle Merge statement. If the row exists update it, if not insert it.

MERGE INTO Table1 a
USING Table2 b
ON (a.id = b.id)
WHEN MATCHED THEN
UPDATE set a.Date = b.Date
WHEN NOT MATCHED THEN
INSERT (id, date)
VALUES (b.id, b.Date);