I am trying to do something like this in HIVE:
insert into table abc
select a.plc,b.direction
from (select c.plc from test t JOIN central c ON t.id = c.boxno) a ,
(select c.direction from test t JOIN central c ON t.id = c.boxno) b;
Please suggest what's wrong in this ?
I feel this query can be modified to obtain the result in a better way. Try this instead:
insert into table abc
select c.plc,c.direction
from test t
JOIN central c ON t.id = c.boxno;
Wont the required output be same? In case you are trying to achieve something else functionally, please elaborate.
Related
My query is working but it takes time to display the data. Can you help me to make it quick.
$sql="SELECT allinvty3.*, stock_transfer_tb.* from stock_transfer_tb
INNER JOIN allinvty3 on stock_transfer_tb.in_code = allinvty3.in_code
where stock_transfer_tb.in_code NOT IN (SELECT barcode.itemcode from barcode where stock_transfer_tb.refnumber = barcode.refitem)";
I would recommend using the following query:
SELECT
a.*,
s.*
FROM stock_transfer_tb s
INNER JOIN allinvty3 a
ON s.in_code = a.in_code
WHERE
NOT EXISTS (SELECT 1 FROM barcode b
WHERE s.refnumber = b.refitem AND s.in_code = b.itemcode);
If this still doesn't give you the performance you want, then you should look into adding indices on all columns involved in the join and where clause.
I have a simple query:
SELECT * FROM Products p
LEFT JOIN SomeTable st ON st.SomeId = p.SomeId AND st.SomeOtherId = p.SomeOtherId
So far so good.
But the first join to SomeId can be NULL, In that case the check should be IS NULL, and that's where the join fails. I tried to use a CASE, but can't get that to work also.
Am I missing something simple here?
From Undocumented Query Plans: Equality Comparisons.
SELECT *
FROM Products p
LEFT JOIN SomeTable st
ON st.SomeOtherId = p.SomeOtherId
AND EXISTS (SELECT st.SomeId INTERSECT SELECT p.SomeId)
In SQL Server, I know for sure that the following query;
SELECT things.*
FROM things
LEFT OUTER JOIN (
SELECT thingreadings.thingid, reading
FROM thingreadings
INNER JOIN things on thingreadings.thingid = things.id
ORDER BY reading DESC LIMIT 1) AS readings
ON things.id = readings.thingid
WHERE things.id = '1'
Would join against thingreadings only once the WHERE id = 1 had restricted the record set down. It left joins against just one row. However in order for performance to be acceptable in postgres, I have to add the WHERE id= 1 to the INNER JOIN things on thingreadings.thingid = things.id line too.
This isn't ideal; is it possible to force postgres to know that what I am joining against is only one row without explicitly adding the WHERE clauses everywhere?
An example of this problem can be seen here;
I am trying to recreate the following query in a more efficient way;
SELECT things.id, things.name,
(SELECT thingreadings.id FROM thingreadings WHERE thingid = things.id ORDER BY id DESC LIMIT 1),
(SELECT thingreadings.reading FROM thingreadings WHERE thingid = things.id ORDER BY id DESC LIMIT 1)
FROM things
WHERE id IN (1,2)
http://sqlfiddle.com/#!15/a172c/2
Not really sure why you did all that work. Isn't the inner query enough?
SELECT t.*
FROM thingreadings tr
INNER JOIN things t on tr.thingid = t.id AND t.id = '1'
ORDER BY tr.reading DESC
LIMIT 1;
sqlfiddle demo
When you want to select the latest value for each thingID, you can do:
SELECT t.*,a.reading
FROM things t
INNER JOIN (
SELECT t1.*
FROM thingreadings t1
LEFT JOIN thingreadings t2
ON (t1.thingid = t2.thingid AND t1.reading < t2.reading)
WHERE t2.thingid IS NULL
) a ON a.thingid = t.id
sqlfiddle demo
The derived table gets you the record with the most recent reading, then the JOIN gets you the information from things table for that record.
The where clause in SQL applies to the result set you're requesting, NOT to the join.
What your code is NOT saying: "do this join only for the ID of 1"...
What your code IS saying: "do this join, then pull records out of it where the ID is 1"...
This is why you need the inner where clause. Incidentally, I also think Filipe is right about the unnecessary code.
I need help to optmize the SQL logic in one of my functions. Please, note that I am not able to use store procedure.
Here is my table. It will be initialized using #MainTable that contains a lot of records.
DECLARE TABLE #ResultTable
(
ResultValue INT
)
These are tables that stores some parameters - they can be emty too.
DECLARE TABLE #ParameterOne (ParameterOne INT)
DECLARE TABLE #ParameterTwo (ParameterOne NVARCHAR(100))
...
DECLARE TABLE #ParameterN(ParameterN TINYINT)
Now, I need to join a lot of tables to my #MainTable in order to select from it only some of its records.
The selected records depend on the information stored in the parameters table.
So, my current solution is:
INSERT INTO ResultTable(ResultValue)
SELECT ResultValue
FROM MainTable M
INNER JOIN #MainOne MO
ON M.ID=MO.ID
....
INNER JOIN #MainN MN
ON M.IDN=MN.ID
WHERE (EXISTS (SELECT 1 FROM #ParameterOne WHERE ParameterOne=MO.ID) OR NOT EXISTS (SELECT 1 FROM #ParameterOne))
AND
...
AND
(EXISTS (SELECT 1 FROM #ParameterN WHERE ParameterN=MN.Name) OR NOT EXISTS (SELECT 1 FROM #ParameterN ))
So, the idea is to add the records only if they match the current criteria from the parameters tables.
Because I am not able to use procedure to build dynamic query I am using the WHERE clause with combinations of EXISTS and NOT EXISTS for each parameter table.
The problem is that it works slower when I am adding more and more parameters table. Is there an other way to do this without using a lot of IF/ELSE statements checking what parameter table has records - it will make the function a lot bigger and difficult for read.
And ideas and advices are welcomed.
Good question.
Try the following one:
INSERT INTO ResultTable(ResultValue)
SELECT ResultValue
FROM MainTable M
INNER JOIN (SELECT * FROM #MainOne WHERE (EXISTS (SELECT 1 FROM #ParameterOne WHERE ParameterOne=#MainOne.ID) OR NOT EXISTS (SELECT 1 FROM #ParameterOne))) MO
ON M.ID=MO.ID
....
INNER JOIN (SELECT * FROM #MainN WHERE (EXISTS (SELECT 1 FROM #ParameterN WHERE ParameterOne=#MainN.Name OR NOT EXISTS (SELECT 1 FROM #ParameterN))) MO
ON M.IDN=MN.ID
Advantages:
Result of the JOIN is more quickly, because it does not process all data (it is already filtered)
It looks more simple for adjusting
What's the best way to do something like this in T-SQL?
SELECT DISTINCT ID
FROM Members,
INNER JOIN Comments ON Members.MemberId = Comments.MemberId
WHERE COUNT(Comments.CommentId) > 100
Trying to get the members who have commented more than 100 times. This is obviously invalid code but what's the best way to write this?
This should get you what you're after. I'm not saying this is the absolutely best way of doing it, but it's unlikely you'll find anything better.
SELECT ID
FROM Members
INNER JOIN Comments
ON Members.MemberId = Comments.MemberId
GROUP BY ID
HAVING COUNT(*) > 100
I like using a subquery.
SELECT DISTINCT m.ID
FROM Members m
WHERE (SELECT COUNT(c.CommentID)
FROM Comments c
WHERE c.MemberID = m.MemberID) > 100
Try
SELECT ID
FROM Members
INNER JOIN (SELECT MemberID FROM Comments
GROUP BY MemberID HAVING COUNT(CommentId) > 100)
AS CommentCount ON Members.MemberID = CommentCount.CommentID