How can I fetch distinct values from an inner query?
Scenario:
I have a table: MyData with columns ID and Starttime.
ID is a hex string
and starttime is a time stamp.
ID and starttime can be a null.
Here is how the table looks:
ID StartTime
01655a70 2014-10-24 06:22:03.0
01655a70 2014-10-24 06:22:03.0
b752 2014-10-15 03:19:03.0
b752 <null>
3922b 2014-10-15 03:19:03.0
d98cb <null>
I want to get distinct ID values that do not have any NULL value in it's starttime column.
Expected result should be:
01655a70
3922b
I have tried:
select distinct(ID) from Mydata where ID in (select ID from MyData where id not like '' and starttime is not null)
select distinct(inner.ID) from (select ID from MyData where id not like '' and starttime is not null) as inner
which seems to yield all the ID entries including the ones that have a null value.
Also looked at the SO posts:
http://stackoverflow.com/questions/23278387/options-for-returning-distinct-values-across-an-inner-join
and
http://stackoverflow.com/questions/13149857/select-distinct-on-inner-join-query-filtering-by-multiple-values-on-a-single-col
The select distinct query seems straight forward to me, is there something obviously wrong here?
Additional Information:
My DB is a MS Access DB, *.accdb type database.
select t.id from (
select id, count(*) as n_all,
count(starttime) as n_time
from Mydata
group by id
) t
where t.n_all = t.n_time;
count(*) counts all rows
count(col) counts not null col values
Another option:
select distinct m1.id from Mydata m1
where not exists (select 1 from Mydata m2 where m2.id = m1.id and m2.starttime is null);
Your query:
select distinct(ID) from Mydata
where ID in (select ID from MyData
where id not like '' and starttime is not null);
id not like '' this condition doesn't test for null. Use id is not null instead
The subquery just returns all the ids which have not null starttime. So your query doesn't check all the values of starttime for each id and it is equivalent to:
select distinct ID from MyData where id not like '' and starttime is not null;
The second query does the same thing as the first query - you just added an alias for your subquery.
Related
I have a many to many table called dbo.ObjectOwner having following columns:
ObjectId | OwnerId | StartDate |EndDate
Where ObjectId, OwnerId is not a primary key and Startdate and Enddate refer to the dates where Object is owned by Owner.
The query I'm trying to do should return all
ObjectId's where for each ObjectId, it has no associated records where EndDate is null. I.e, return all objects who currently have no owner.
so something like
foreach(objectId in dbo.ObjectOwner)
if (
doesnotexist (records where ObjectId = objectid and EndDate is null)
)
{
add this objectid to the select table
}
I had a look at group by and having, but the following script returns all records
SELECT oo.ObjectId
FROM dbo.ObjectOwner oo
GROUP BY oo.ObjectId
HAVING NOT EXISTS (
SELECT 1
FROM dbo.ObjectOwner
WHERE dbo.ObjectOwner.EndDate = null
)
Thanks in advance
You can use GROUP BY and HAVING. The following works because NULL values are not COUNTed:
SELECT ObjectId
FROM ObjectOwner
GROUP BY ObjectId
HAVING COUNT(*) = COUNT(EndDate)
It can't work if you write <...> = NULL, because NULL can't be equal to something.
SELECT oo.ObjectId
FROM dbo.ObjectOwner oo
GROUP BY oo.ObjectId
HAVING NOT EXISTS (
SELECT 1
FROM dbo.ObjectOwner
WHERE dbo.ObjectOwner.EndDate IS NULL
)
I have a table with following format and I want to get the LotId if Value1 is null for all the rows.
Now If I am doing Select,
Select * from Table1 where Value1 IS null , I am getting back a row .
But I want nothing should be returned as there are two rows which have some value.
I thought of self join , but this can have n number of rows.
Id LotId Value1
-------------------------------------------------
1 LOt0065 NULL
2 LOt0065 SomeValue
3 LOt0065 SomeValue
I think you'll need to use an EXISTS subquery here:
SELECT a.lotid
FROM table1 a
WHERE NOT EXISTS (
SELECT 1
FROM table1 b
WHERE b.lotid = a.lotid
AND b.value1 IS NOT NULL
);
If my syntax is right, then this will show you all records that don't have any NULL values for that lotid:
It uses a SELECT 1 because the subquery doesn't need to show any value, it just needs to match on the outer query.
You compare the table in the inner query to the table in the outer query and match on the common field you're looking at (lotid in this case)
This could also be done with a NOT IN clause.
Does this give you the result you want?
I want to fill the joining date and id by creating a new view and output should be like second image
you might be looking for something like:
UPDATE mytable
SET tofill.ID = fillvalues.ID
,tofill.JOININGDATE = fillvalues.JOININGDATE
FROM mytable tofill
INNER JOIN
( SELECT DISTINCT ID, JOININGDATE, NAME
FROM mytable
WHERE ID IS NOT NULL
AND JOININGDATE IS NOT NULL
) fillvalues
ON tofill.NAME = fillvalues.NAME
WHERE tofill.ID IS NULL
OR tofill.JOININGDATE IS NULL
;
I am not familiar with Oracle, but statement should be teh same or similiar
I've a scenario where I need to write sql query base on result of other query.
Consider the table data:
id attribute
1 a
1 b
2 a
3 a
3 b
3 c
I want to write query to select id base on attribute set.
I mean first I need to check attribute of id 1 using this query:
select attribute from table where id = 1
then base on this result I need to select subset of attribute. like in our case 1(a,b) is the subset of 3(a,b,c). My query should return 3 on that case.
And if I want to check base on 2(a) which is the subset of 1(a,b) and 3(a,b,c), it should return 1 and 3.
I hope, it's understandable. :)
You could use this query.
Logic is simple: If there isn't any item in A and isn't in B --> A is subset of B.
DECLARE #SampleData AS TABLE
(
Id int, attribute varchar(5)
)
INSERT INTO #SampleData
VALUES (1,'a'), (1,'b'),
(2,'a'),
(3,'a'),(3,'b'),(3,'c')
DECLARE #FilterId int = 1
;WITH temp AS
(
SELECT DISTINCT sd.Id FROM #SampleData sd
)
SELECT * FROM temp t
WHERE t.Id <> #FilterId
AND NOT EXISTS (
SELECT sd2.attribute FROM #SampleData sd2
WHERE sd2.Id = #FilterId
AND NOT EXISTS (SELECT * FROM #SampleData sd WHERE sd.Id = t.Id AND sd.attribute = sd2.attribute)
)
Demo link: Rextester
I would compose a query for that in three steps: first I'd get the attributes of the desired id, and this is the query you wrote
select attribute from table where id = 1
Then I would get the number of attributes for the required id
select count(distinct attribute) from table where id = 1
Finally I would use the above results as filters
select id
from table
where id <> 1 and
attribute in (
select attribute from table where id = 1 /* Step 1 */
)
group by id
having count(distinct attribute) = (
select count(distinct attribute) from table where id = 1 /* Step 2 */
)
This will get you all the id's that have a number of attributes among those of the initially provided id equal to the number the initial id has.
I'm trying to figure out how to fill in values that are missing from one column with the non-missing values from other rows that have the same value on a given column. For instance, in the below example, I'd want all the "1" values to be equal to Bob and all of the "2" values to be equal to John
ID # | Name
-------|-----
1 | Bob
1 | (null)
1 | (null)
2 | John
2 | (null)
2 | (null)
`
EDIT: One caveat is that I'm using postgresql 8.4 with Greenplum and so correlated subqueries are not supported.
CREATE TABLE bobjohn
( ID INTEGER NOT NULL
, zname varchar
);
INSERT INTO bobjohn(id, zname) VALUES
(1,'Bob') ,(1, NULL) ,(1, NULL)
,(2,'John') ,(2, NULL) ,(2, NULL)
;
UPDATE bobjohn dst
SET zname = src.zname
FROM bobjohn src
WHERE dst.id = src.id
AND dst.zname IS NULL
AND src.zname IS NOT NULL
;
SELECT * FROM bobjohn;
NOTE: this query will fail if more than one name exists for a given Id. (and it won't touch records for which no non-null name exists)
If you are on a postgres version >-9, you could use a CTE to fetch the source tuples (this is equivalent to a subquery, but is easier to write and read (IMHO). The CTE also tackles the duplicate values-problem (in a rather crude way):
--
-- CTE's dont work in update queries for Postgres version below 9
--
WITH uniq AS (
SELECT DISTINCT id
-- if there are more than one names for a given Id: pick the lowest
, min(zname) as zname
FROM bobjohn
WHERE zname IS NOT NULL
GROUP BY id
)
UPDATE bobjohn dst
SET zname = src.zname
FROM uniq src
WHERE dst.id = src.id
AND dst.zname IS NULL
;
SELECT * FROM bobjohn;
UPDATE tbl
SET name = x.name
FROM (
SELECT DISTINCT ON (id) id, name
FROM tbl
WHERE name IS NOT NULL
ORDER BY id, name
) x
WHERE x.id = tbl.id
AND tbl.name IS NULL;
DISTINCT ON does the job alone. Not need for additional aggregation.
In case of multiple values for name, the alphabetically first one (according to the current locale) is picked - that's what the ORDER BY id, name is for. If name is unambiguous you can omit that line.
Also, if there is at least one non-null value per id, you can omit WHERE name IS NOT NULL.
If you know for a fact that there are no conflicting values (multiple rows with the same ID but different, non-null names) then something like this will update the table appropriately:
UPDATE some_table AS t1
SET name = (
SELECT name
FROM some_table AS t2
WHERE t1.id = t2.id
AND name IS NOT NULL
LIMIT 1
)
WHERE name IS NULL;
If you only want to query the table and have this information filled in on the fly, you can use a similar query:
SELECT
t1.id,
(
SELECT name
FROM some_table AS t2
WHERE t1.id = t2.id
AND name IS NOT NULL
LIMIT 1
) AS name
FROM some_table AS t1;