Use case:
I have the customer_id and the task_id.
The database will always contain registers with a filled customer_id and empty task_id.
Sometimes will have the task_id filled. (as the example below)
Example 1
SELECT *
FROM table
WHERE customer_id = 11422412
AND task_id = 28870055
Here I expect to return the last two rows.
Example 2
SELECT *
FROM table
WHERE customer_id = 11432515
AND task_id = 22256884
Here I expect to return the only empty row.
Question:
How do I create a SQL Query to make sure that, in case the task_id exists in the database, I only return the records with task_id?
You could do something like the following with LIMIT. This will match the empty task_id and the set task_id (if it exists), order them so that the row with non-empty task_id comes first (if it exists), then return only the first one. (NULLS LAST is default sorting behavior in Postgre)
SELECT *
FROM table
WHERE customer_id = 11432515
AND (task_id = 22256884 OR task_id IS NULL)
ORDER BY task_id
LIMIT 1
I am assuming that you always want exactly one row like in your examples.
But there are other ways of doing it depending on your specific scenario (if your final query is more complicated than your examples).
Edited to add another way to handle case where more than one row matches customer_id and task_id:
SELECT *
FROM table t1
WHERE customer_id = 11432515
AND (task_id = 22256884
OR (
task_id is null
AND NOT EXISTS (SELECT * FROM table t2 WHERE t2.customer_id = 11432515 AND t2.task_id = 22256884)
)
)
This doesn't look super elegant, but it should work and you could use it as a starting point at least.
Related
Setup: Postgresql table with a customer_id and a request_id column (+ additional not relevant data).
The rows with customer_id set to NULL work as a fallback/default.
Example what the table looks like:
Goal: I want to select all rows from the table for a given customer (e.g. where customer_id = 2).
For any existent request_id: If there are no entries for the given customer, return the fallback rows (where customer is null).
So the result should look like this:
Any idea how to write the select statement for postgresql? I'm kind of stuck and couldn't really find anything helpful so far. Thanks!
This is a strange requirement.
select t.*
from t
where t.customer_id = 2 or
(t.customer_id is null and
not exists (select 1 from t t2 where t2.request_id = t.request_id and t2.customer_id = 2)
);
For performance, I would recommend an index on (request_id, customer_id).
My tables are like so:
Tile
Tile
---------------------------------
Id integer not null primary key
TestSet
TestSet
--------------------------------
Id integer not null primary key,
TileId integer not null,
CreatedAt datetime not null,
Outcome boolean
There is a 1:n relationship between Tile and TestSet.
I want to get the tiles that have a testSet with a true Outcome value on the most recent testSet (ordered by the CreatedAt column). My first attempt at it doesn't work as I want it to.
SELECT * FROM Tile
JOIN (SELECT TileId FROM (SELECT * FROM TestSet
WHERE tileId == 'Tile1'
ORDER BY __createdAt DESC
LIMIT 1)
WHERE Outcome=1) as ts ON ts.TileId == Tile.id;
The problem with the above statement is that the WHERE clause in the most inner SELECT statement is hardcoded.
Here's how I broke up the process:
Grab the most recent testSet.
SELECT only the tileId column from that testSet.
JOIN the tile table on the above statements to get a list of all the tiles.
I feel like I'm thinking about this the wrong way and I shouldn't really be doing a JOIN. But I don't have enough SQL experience to know exactly how to go about this problem. I'm using SQLite specifically in a mobile app, so are there any SQLite statements that can help me get the correct set of tiles?
Here's an alternate method. Since the tileid is already there in TestSet, this example uses only TestSet, but you can feel free to JOIN it with Tile table.
select *
from testset t1
where createdat in
(
-- search the same table for the tileid and also ensure outcome is 1
-- sort it by createAt latest to oldest date and choose only the first
-- record
select createdat
from testset t2
where
t2.tileid = t1.tileid
and outcome = 1
order by t2.createdat desc
limit 1
);
Example: http://sqlfiddle.com/#!7/91548/3
SELECT Id FROM Tile
JOIN (SELECT TileId, Outcome, MAX(CreatedAt)
FROM TestSet
GROUP BY TileId, Outcome
) AS ts
ON ts.TileId == Tile.id
WHERE Outcome = 1;
I have a search jsp, which has more than one criteria( ID OR NAME OR DATE OR ...) for searching the database. I need a single select query to satisfy all the condition. I have written the select query partially, but it is not working well. Please help me in finishing the query
select * from table 1
where Id in ( select id from table 1 where ( those three conditions here)
i have (1=? or id=?)
and (1=? or name=?)
and (1=? or date =?)
but it returns the full table. I know those three condition returns true. How to modify that in order to obtain the result. I don't want any stored procedure, as i am a newbie
If your conditions are true for every row, you'll get the full table.
For example, if your variable is 1, 1 = 1 will be true, and every row will be returned.
p,s, I don't understand why you've nested the select.
You've got a redundant subquery.
I assume the first parameter will be 1 if the second parameter is null, and 0 if the second parameter is not null; likewise the 3rd parameter will 1 if the 4th parameter is null, and 0 if the 4th parameter is not null, etc.?
Try this:
select * from table
where (1=? or id=?)
and (1=? or name=?)
and (1=? or date =?)
For example, if the user was searching by name I'd expect the parameters to be something like (1,NULL,0,'SMITH',1,NULL).
(Also, you can't use 1 for the table alias.)
select * from table 1
where Id in ( select
(case
when (1=? or id=?) and (1=? or name=? ) and (1=? or date =?) then id
end) as id from table 1 )
I hope this is what you are looking for
i have loanTable that contain two field loan_id and status
loan_id status
==============
1 0
2 9
1 6
5 3
4 5
1 4 <-- How do I select this??
4 6
In this Situation i need to show the last Status of loan_id 1 i.e is status 4. Can please help me in this query.
Since the 'last' row for ID 1 is neither the minimum nor the maximum, you are living in a state of mild confusion. Rows in a table have no order. So, you should be providing another column, possibly the date/time when each row is inserted, to provide the sequencing of the data. Another option could be a separate, automatically incremented column which records the sequence in which the rows are inserted. Then the query can be written.
If the extra column is called status_id, then you could write:
SELECT L1.*
FROM LoanTable AS L1
WHERE L1.Status_ID = (SELECT MAX(Status_ID)
FROM LoanTable AS L2
WHERE L2.Loan_ID = 1);
(The table aliases L1 and L2 could be omitted without confusing the DBMS or experienced SQL programmers.)
As it stands, there is no reliable way of knowing which is the last row, so your query is unanswerable.
Does your table happen to have a primary id or a timestamp? If not then what you want is not really possible.
If yes then:
SELECT TOP 1 status
FROM loanTable
WHERE loan_id = 1
ORDER BY primaryId DESC
-- or
-- ORDER BY yourTimestamp DESC
I assume that with "last status" you mean the record that was inserted most recently? AFAIK there is no way to make such a query unless you add timestamp into your table where you store the date and time when the record was added. RDBMS don't keep any internal order of the records.
But if last = last inserted, that's not possible for current schema, until a PK addition:
select top 1 status, loan_id
from loanTable
where loan_id = 1
order by id desc -- PK
Use a data reader. When it exits the while loop it will be on the last row. As the other posters stated unless you put a sort on the query, the row order could change. Even if there is a clustered index on the table it might not return the rows in that order (without a sort on the clustered index).
SqlDataReader rdr = SQLcmd.ExecuteReader();
while (rdr.Read())
{
}
string lastVal = rdr[0].ToString()
rdr.Close();
You could also use a ROW_NUMBER() but that requires a sort and you cannot use ROW_NUMBER() directly in the Where. But you can fool it by creating a derived table. The rdr solution above is faster.
In oracle database this is very simple.
select * from (select * from loanTable order by rownum desc) where rownum=1
Hi if this has not been solved yet.
To get the last record for any field from a table the easiest way would be to add an ID to each record say pID. Also say that in your table you would like to hhet the last record for each 'Name', run the simple query
SELECT Name, MAX(pID) as LastID
INTO [TableName]
FROM [YourTableName]
GROUP BY [Name]/[Any other field you would like your last records to appear by]
You should now have a table containing the Names in one column and the last available ID for that Name.
Now you can use a join to get the other details from your primary table, say this is some price or date then run the following:
SELECT a.*,b.Price/b.date/b.[Whatever other field you want]
FROM [TableName] a LEFT JOIN [YourTableName]
ON a.Name = b.Name and a.LastID = b.pID
This should then give you the last records for each Name, for the first record run the same queries as above just replace the Max by Min above.
This should be easy to follow and should run quicker as well
If you don't have any identifying columns you could use to get the insert order. You can always do it like this. But it's hacky, and not very pretty.
select
t.row1,
t.row2,
ROW_NUMBER() OVER (ORDER BY t.[count]) AS rownum from (
select
tab.row1,
tab.row2,
1 as [count]
from table tab) t
So basically you get the 'natural order' if you can call it that, and add some column with all the same data. This can be used to sort by the 'natural order', giving you an opportunity to place a row number column on the next query.
Personally, if the system you are using hasn't got a time stamp/identity column, and the current users are using the 'natural order', I would quickly add a column and use this query to create some sort of time stamp/incremental key. Rather than risking having some automation mechanism change the 'natural order', breaking the data needed.
I think this code may help you:
WITH cte_Loans
AS
(
SELECT LoanID
,[Status]
,ROW_NUMBER() OVER(ORDER BY (SELECT 1)) AS RN
FROM LoanTable
)
SELECT LoanID
,[Status]
FROM LoanTable L1
WHERE RN = ( SELECT max(RN)
FROM LoanTable L2
WHERE L2.LoanID = L1.LoanID)
2 records in above image are from Db, in above table Constraint are (SID and LINE_ITEM_ID),
SID and LINE_ITEM_ID both column are used to find a unique record.
My issues :
I am looking for a query it should fetch the recored from DB depending on conditions
if i search for PART_NUMBER = 'PAU43-IMB-P6'
1. it should fetch one record from DB if search for PART_NUMBER = 'PAU43-IMB-P6', no mater to which SID that item belong to if there is only one recored either under SID =1 or SID = 2.
2. it should fetch one record which is under SID = 2 only, from DB on search for PART_NUMBER = 'PAU43-IMB-P6', if there are 2 items one in SID=1 and other in SID=2.
i am looking for a query which will search for a given part_number depending on Both SID 1 and 2, and it should return value under SID =2 and it can return value under SID=1 only if the there are no records under SID=2 (query has to withstand a load of Million record search).
Thank you
Select *
from Table
where SID||LINE_ITEM_ID = (
select Max(SID)||Max(LINE_ITEM_ID)
from table
where PART_NUMBER = 'PAU43-IMB-P6'
);
If I understand correctly, for each considered LINE_ITEM_ID you want to return only the one with the largest value for SID. This is a common requirement and, as with most things in SQL, can be written in many different ways; the best performing will depend on many factors, not least of which is the SQL product you are using.
Here's one possible approach:
SELECT DISTINCT * -- use a column list
FROM YourTable AS T1
INNER JOIN (
SELECT T2.LINE_ITEM_ID,
MAX(T2.SID) AS max_SID
FROM YourTable AS T2
GROUP
BY T2.LINE_ITEM_ID
) AS DT1 (LINE_ITEM_ID, max_SID)
ON T1.LINE_ITEM_ID = DT1.LINE_ITEM_ID
AND T1.SID = DT1.max_SID;
That said, I don't recall seeing one that relies on the UNION relational operator. You could easily rewrite the above using the INTERSECT relational operator but it would be more verbose.
Well in my case it worked something like this:
select LINE_ITEM_ID,SID,price_1,part_number from (
(select LINE_ITEM_ID,SID,price_1,part_number from Table where SID = 2)
UNION
(select LINE_ITEM_ID,SID,price_1,part_number from Table SID = 1 and line_item_id NOT IN (select LINE_ITEM_ID,SID,price_1,part_number from Table SID = 2)))
This query solved my issue..........