In Oracle, I would like do an update on a table for the last occurrence based on select in list, something like :
UPDATE table t1
set t1.fieldA = 0
where t1.id in (
select t2.id, max(t2.TIMESTAMP)
from table t2
where t2.id in (1111,2222,33333)
group by t2.id
);
This query does not works, I received an error "too many values".
Any ideas?
Thanks
Your subselect has 2(too many) fields so it cant't be compared with the id.
compare the timestamp with the max timestamp.
UPDATE table t1 set t1.fieldA = 0
where t1.TIMESTAMP = (select max(t2.TIMESTAMP) from table t2 where t2.id = t1.id )
and id in (1111,2222,33333)
I believe oracle supports multiple columns IN, so you could try:
UPDATE table t1
set t1.fieldA = 0
where
(t1.id,t1.timestamp) in ( select t2.id, max(t2.TIMESTAMP) from table t2 where t2.id in (1111,2222,33333) group by t2.id );
Essentially if you're providing a subquery to the right side of the IN that has a result set with two columns, then you have to provide the names of both the columns in brackets on the left side of the IN
Incidentally, I've never liked updating based on a max value if the requirement is that only one row be updated, as two rows with the same max value will both be updated. This kind of query is better:
Update table
Set fieldA=0
Where rowid in(
select rowid from (
select rowid, row_number() over(partition by id order by timestamp desc
) as rown from table
) where rown=1)
If, however, your primary key on the table includes the time stamp as part of the compound, then there is no concern of here being two rows with the same ID/timestamp.. it's just rarely the case!
Related
I have two tables and i want to use some records from first table and get last related record from another one.
You can see my tables
I want to join table 1 with last record of table 2. (creationDate = 2018-07-20)
If you simply want to get the latest record in table 2 for every ID in table one then this will work:
select t1.ID, t1.Name, q.ID, q.CreationDate
from table1 t1
outer apply
(
select top 1 t2.ID, t2.CreationDate
from table2 t2
where t2.tbl_1_Id = t1.ID
order by t2.CreationDate desc
)q
How do you write a update statement with a Sub-Select in an Oracle Environment (SQL Developer)?
Example: UPDATE table SET column = (SELECT....)
Every time I try this it gives me ORA-01427 "Sub select returns more then one row" even if there is no WHERE clause..
Based on the understanding of your question I'd suggest use Merge statement.
Merge into Table1
Using
(SELECT * from table2 where condition) Temp
On (Table1.columname condition Temp.columname)
When matched Then update Set Table1.column_name = Temp.column_name;
Table1 is the table where you want to update the records.
Table2 is the table from which you want to get the data (The sub query which you are talking about )
Using this merge statement you will be able to update n number of rows.
If you want to update multiple rows, you can either use a MERGE statement (as in #jackkds7's answer above) or you can use a filter on your subselect:
UPDATE table t1
SET column = ( SELECT column FROM table2 t2 WHERE t2.key = t1.key );
If there aren't matches in table2 for all the records in table then column will be set to NULL for the non-matches. To avoid that, add a WHERE EXISTS clause:
UPDATE table t1
SET column = ( SELECT column FROM table2 t2 WHERE t2.key = t1.key )
WHERE EXISTS ( SELECT 1 FROM table2 t2 WHERE t2.key = t1.key );
Oh and in the event that key is not unique for table2, you can aggregate (up to you to figure out which function would be best):
UPDATE table t1
SET column = ( SELECT MAX(column) FROM table2 t2 WHERE t2.key = t1.key )
WHERE EXISTS ( SELECT 1 FROM table2 t2 WHERE t2.key = t1.key );
Hope this helps.
I think it would help if you posted your actual query.
In essence, the "inner" select would be executed for each row that would be updated. This inner select query is called a correlated subquery:
UPDATE table t SET t.column = (
select ot.othercolumn from othertable ot
where ot.fk = t.id --This is the correlation part, that finds
--he right value for the row you are currently updating
)
You must ensure the subquery you use will always return just a single row and a single column for every time it runs (that is, for every row that is going to be updated). If needed, you can use MAX(), or ROWNUM to ensure you always only get 1 value
More examples:
Using Correlated Subqueries
I'm trying merging 2 tables as follow
SELECT * FROM T1
LEFT JOIN T2 ON T1.EMPnum = T2.EMPnum
The above works well but I need the joining to use only the first appearance of the common key EMPnum record in table T2 so that the query returns exactly the same number of rows as T1
Thanks Avi
SQL tables are inherently unordered, so there is no such thing as a "first" key. In most databases, you can do something like this:
with t2 as (
select t2.*, row_number() over (partition by EMPnum order by id) as seqnum
from t2
)
select *
from t1 left join
t2
on t1.EMPnum = t2.EMPnum and t2.seqnum = 1;
Here id is just any column that specifies the ordering. If none exist, you can use EMPnum to get an arbitrary row.
Using the below query to copy records from one table to another, but i get error
insert into table1 (datestamp)
select datestamp
from table2
where table1.datestamp is null
I want to copy records of datestamp from table 2 to table 1 where datestamp in table 1 is null.
Is this what you mean?
insert into table1 (datestamp)
select datestamp
from table2
where table2.datestamp is null
You are referencing table1 datestamp in the where clause and this is not allowed.
Perhaps you really want an update. If so, you need a way to link the two tables:
update t1
set datestamp = t2.datestamp
from table1 t1 join
table2 t2
on t1.id = t2.id
where t1.datestamp is null
I'm assuming the tables are tied together by some unique id? We'll call that tableID.
UPDATE table1 t1, table2 t2
SET t1.datestamp = t2.datestamp
WHERE t1.datestamp IS NULL
AND t1.tableID = t2.tableID
There is a table with Columns as below:
Id : long autoincrement;
timestamp:long;
price:long
Timestamp is given as a unix_time in ms.
Question: what is the average time difference between the records ?
First thought is a sub-query grabbing the record immediately previous:
SELECT timestamp -
(select top 1 timestamp from Table T1 where T1.Id < Table.Id order by Id desc)
FROM Table
Then you can take the average of that:
SELECT AVG(delta)
from (SELECT timestamp -
(select top 1 timestamp from Table T1 where T1.Id < Table.Id order by Id desc) as delta
FROM Table) T
There will probably need to be some handling of the null that results for the first row, but I haven't tested to be sure.
In SQL Server, you could write something like that to get that information:
SELECT
t1.ID, t2.ID,
DATEDIFF(MILLISECOND, t2.PriceTime, test2.PriceTime)
FROM table t1
INNER JOIN table t2 ON t2.ID = t1.ID-1
WHERE t1.ID > (SELECT MIN(ID) FROM table)
and if you're only interested in the AVG across all entries, you could use:
SELECT
AVG(DATEDIFF(MILLISECOND, t2.PriceTime, test2.PriceTime))
FROM table t1
INNER JOIN table t2 ON t2.ID = t1.ID-1
WHERE t1.ID > (SELECT MIN(ID) FROM table)
Basically, you need to join the table with itself, and use "t1.ID = t2.ID-1" to associate item no. 2 in one table with item no. 1 in the other table and then calculate the time difference between the two. In order to avoid accessing item no. 0 which doesn't exist, use the "T1.ID > (SELECT MIN(ID) FROM table)" clause to start from the second item.
Marc
At a guess:
SELECT AVG(timestamp)
I think you need to provide more information in your question for us to help.
If you mean difference between each-other row:
select AVG(x) from (
select a.timestamp - b.timestamp as x
from table a, table b -- this multiplies a*b ) sub
SELECT AVG(T2.Timestamp - T1.TimeStamp)
FROM Table T1
JOIN Table T2 ON T2.ID = T1.ID + 1
try this
Select Avg(E.Timestamp - B.Timestamp)
From Table B Join Table E
On E.Timestamp =
(Select Max(Timestamp)
From Table
Where Timestamp < R.Timestamp)