I'm trying to update table a with data from some of the columns in table b. Column names are matching in both tables, cannot figure out the syntax, can anyone help?
This is what I want to do (expressed out-of-syntax):
UPDATE table_a
SET table_a.col1 = table_b.col1, table_a.col2 = table_b.col2
WHERE table_a.id = table_b.id
Maybe (probably) I would need some kind of JOIN-clause, but I haven't gotten my head around those yet.... :-/
You can update your table using a JOIN of the two tables:
UPDATE table_a a
INNER JOIN table_b b ON a.id = b.id
SET a.col1 = b.col1, a.col2 = b.col2
I see you are on MYSQL. Not sure if the version above works. If not, try:
UPDATE table_a a
INNER JOIN table_b b
SET a.col1 = b.col1, a.col2 = b.col2
WHERE a.id = b.id
Ok, so I found it myself... :-)
MERGE (without using the WHEN NOT MATCHED clause)is the answer to my problem.
My solution:
MERGE INTO table_a
USING table_b
ON a.id=b.id
WHEN MATCHED THEN UPDATE SET
col1 = b.col1, col2 = b.col2;
Related
I want to update the fields of a table WHERE the combination of three other attributes is IN another table. I am having some difficulties with the syntax, so any help is appreciated.
You would normally use EXISTS for this:
SELECT *
FROM a
WHERE EXISTS (
SELECT 1
FROM b
WHERE a.col1 = b.col1 AND a.col2 = b.col2 AND a.col3 = b.col3
)
Convert the above to an UPDATE query.
I am getting an error by running an update, but I can not figure out where the issue is in Netezza. I appreciate some help.
ERROR [42S02] ERROR: relation does not exist DEVML_WORK.AGRINSHPUN.A
update Table A
set A.COL1 = B.COL2
from A left outer join B
on A.CU_NUM=B.CU_NUM;
In general performance on correlated updates in Netezza is slow. Below are two examples that will get your query to work. The second in my experience speeds up large updates.
-- Slow but works
update Table A
set A.COL1 = B.COL2
from B
where A.CU_NUM=B.CU_NUM;
--Faster
update A set col1 = sub.col2
from (select a.rowid as rown, b.COL2
from A a inner join
B b
on a.cu_num= b.cu_num) sub
where rowid = sub.rown;
So I have some procs I inherited that I am trying to clean up. One of the things I see over and over in them is the following:
Update Table_A
Set A.ColX = B.Colx
From Table_A A
Join Table_B B on B.col1 =A.col1
and B.col2 = A.col2
Update Table_A
Set A.ColX = B.Colx
From Table_A A
Join Table_B B on a.col1 =b.col1
and B.col2 is null
Now , I have tried to combine these to make them a single query using the following different final lines (not at the same time!):
1) and (B.col2 = A.col2 or B.col2 is null)
2) and (isnull(B.col2,'') = COALESCE(a.col2, ''))
However, it always seems to do one of the updates, not both. I feel like I am missing something rather obvious, Is there a good way to combine these two queries?
thanks
This query should work:
Update Table_A
Set A.ColX = B.Colx
From Table_A A
Join Table_B B on B.col1 = A.col1
and (B.col2 = A.col2 OR or B.col2 is null)
which you said you tried - but you may try it as a SELECT first and see what the results are. That may shed some light on why you're not getting the results you expect.
I would expect the following query to work in SQL Server:
Update A
Set ColX = B.Colx
From Table_A A Join
Table_B B
on a.col1 = b.col1 and
(B.col2 = A.col2 or B.col2 is null);
Notes:
You should use the alias defined in the from clause after the update. My understanding is that if you use the table name and the table is not in the from clause without an alias, then all rows will be updated.
Although I was pretty sure that SQL Server does not support table aliases in the set, I appear to be wrong about that, as this simple SQL Fiddle shows. Perhaps this was not allowed in some ancient version of SQL Server, and the limitation just stuck with me.
If I have table A and table B, each with one column:
A:
col1
1
2
3
1
B:
col1
1
1
4
and I want all rows from A and the matching rows from B, only when the column has non null value in both tables, which one should I use?
select * from A left join B on A.col1 = B.col1 and A.col1 is not null AND B.col1 is not null;
select * from A left join B on A.col1 = B.col1 where A.col1 is not null OR B.col1 is not null;
select * from A left join B on A.col1 = B.col1 and (A.col1 is not null OR B.col1 is not null;)
My guess is that the first and the third are the same and will provide the desired output.
If you want to skip null values and you want to link both tables only on existing values you should use an INNER JOIN, the null check is redundant:
SELECT A.*
FROM A INNER JOIN B ON A.col1 = B.col1
NULL will never match any other value (not even NULL itself), unless the join condition explicitly uses the IS NULL or IS NOT NULL predicates.
In a comment you said you are checking for more than nulls in this case I would probaly take thederived table or CTE approach. Dervied table shown below as you did not specify which database backend, so I don't know if you can use CTEs.
select
from
(select from tablea where test is not null or test <>'' or test<>'N/A') a
JOin
(select from tableb where test is not null or test <>'' or test<>'N/A')b
ON a.col1 = b.col1
You just need
select * from A left join B on A.col1 = B.col1
NULL will never match anything (when not compared with IS NULLand the like), therefore NULL in A won't match anything in B.
Since you want all the rows from A, below query should work:
select * from A left outer join B on A.col1 = B.col1 where A.col1 is not null and A.col1<>'N/A' and A.col1<>''
http://sqlfiddle.com/#!2/98501/14
This question already has answers here:
Update statement with inner join on Oracle
(15 answers)
Closed 8 years ago.
I need to update all the rows on table A, where A.id = B.id and B.code is some value.
Something like:
UPDATE table_a
SET processed = 'Y'
WHERE table_a.id = table_b.id AND
table_b.code = 'ABC';
Does anyone know the correct way to do this?
Thanks!
Here are quick workaround for your problem.
UPDATE
(
SELECT
a.processed, a.id
FROM
table_a a,
table_b b
WHERE
a.id = b.id
AND
b.code = 'ABC'
) u
SET u.processed = 'Y'
OR
UPDATE table_a a
SET a.processed = 'Y'
WHERE a.id IN
(SELECT b.id FROM table_b b WHERE b.code = 'ABC')
Hope this might Help!
You have to reference second table before you can use it. You can use a subselect:
UPDATE table_a SET processed = 'Y'
WHERE table_a.id = (SELECT table_b.id FROM table_b WHERE table_b.code = 'ABC');
The subselect returns a list of ids from table_b fulfilling the condition table_b.code = 'ABC'. Update will effect those rows in table_a with table_a.id in the list from subselect.