I am trying to extract the nth row of an SQL statement (not the nth row of a table).
Is there an easy way to run a query and read values from specific rows.
I have tried something similar to this but it does not work since rownum tells me what nth record it is in the table.
SELECT * FROM (
SELECT
ROW_NUMBER() OVER(ORDER BY RewardID ASC) AS rownumber,
RewardID,
Name,
Description,
Image,
RewardType,
price
FROM
Reward
) AS num
WHERE
RewardType = 'Electronics' and rownum = 2
Are you using Postgres Or SQLServer? Both have a ROW_NUMBER() window function, but the syntax, especially around subqueries, may be slightly different. I'll assume Postgres.
You query looks good to me, except that the rownum = 2 in your WHERE should presumably be rownumber = 2, since that's what you aliased the ROW_NUMBER() column as. You also presumably don't need the RewardType and rownumber columns in your result, since their values will always be 'Electronics' and 2 respectively. Corrected and formatted for readability, this looks ok to me:
SELECT RewardID, Name, Description, Image, RewardType, price
FROM (
SELECT
ROW_NUMBER() OVER(ORDER BY RewardID ASC) AS rownumber,
RewardID,
Name,
Description,
Image,
RewardType,
price
FROM Reward) AS num
WHERE RewardType = 'Electronics' and rownumber = 2
The only questionable part of that is the WHERE RewardType = 'Electronics'. Should that actually be in the subquery rather than the outer query? The difference is that if it is in the subquery, the row counting will include only reward type 'Electronics', whereas in the outer query, all reward types will be counted. To only count the reward type 'Electronics', modify it as so:
SELECT RewardID, Name, Description, Image, RewardType, price
FROM (
SELECT
ROW_NUMBER() OVER(ORDER BY RewardID ASC) AS rownumber,
RewardID,
Name,
Description,
Image,
RewardType,
price
FROM Reward
WHERE RewardType = 'Electronics') AS num
WHERE rownumber = 2
Edit: Since the comment you just made clarifies what you're really trying to do, I'll add that you should NOT be making an individual query for each row of the data that you want. Whatever interface you are using to your database will have a way of iterating over a query result that uses multiple rows, and if that's what you really need, you should find out how to do that.
You can try using OFFSET/FETCH:
SELECT
RewardID,
Name,
Description,
Image,
RewardType,
price
FROM Reward
WHERE RewardType = 'Electronics'
OFFSET 1 ROWS FETCH NEXT 1 ROWS ONLY
Tell it to OFFSET(skip) row 1 then FETCH(select) 1 row after that, which would be row 2. This removes the need for a sub select.
The key is the order by, try using null in the order by.SELECT * FROM (
SELECT
ROW_NUMBER() OVER(ORDER BY (select null)) AS rownumber,
RewardID,
Name,
Description,
Image,
RewardType,
price
FROM
Reward
) AS num
WHERE
RewardType = 'Electronics' and rownum = 2
Related
I'm trying to make an SQL query that returns the greatest number from a column and its respective id.
For more information I have two columns ID and NUMBER. Both of them have 2 entries and I want to get the highest number with the ID next to it. This is what I tried but didn't success.
SELECT ID, MAX(NUMBER) AS MAXNUMB
FROM TABLE1
GROUP BY ID, MAXNUMB;
The problem I'm experiencing is that it just shows ALL the entries and if I add a "where" expression it just shows the same (all entries [ids+numbers]).
Pd.: Yes, I got what I wanted but only with one column (number) if I add another column (ID) to select it "brokes".
Try:
SELECT
ID,
A_NUMBER
FROM TABLE1
WHERE A_NUMBER = (
SELECT MAX(A_NUMBER)
FROM TABLE1);
Presuming you want the IDs* of the row with the highest number (and not, instead, the highest number for each ID -- if IDs were not unique in your table, for example).
* there may be more than one ID returned if there are two or more IDs with equal maximum numbers
you can try this
Select ID,maxNumber
From
(
SELECT
ID,
(Select Max(NUMBER) from Tmp where Id = t.Id) maxNumber
FROM
Tmp t
)T1
Group By ID,maxNumber
The query you posted has an illegal column name (number) and is group by the alias for the max value, which is illegal and also doesn't make sense; and you can't include the unaliased max() within the group-by either. So it's likely you're actually doing something like:
select id, max(numb) as maxnumb
from table1
group by id;
which will give one row per ID, with the maximum numb (which is the new name I've made up for your numeric column) for each ID. Or as you said you get "ALL the entries" you might have group by id, numb, which would show all rows from the table (unless there are duplicate combinations).
To get the maximum numb and the corresponding id you could group by id only, order by descending maxnumb, and then return the first row only:
select id, max(numb) as maxnumb
from table1
group by id
order by maxnumb desc
fetch first 1 row only
If there are two ID with the same maxnumb then you would only get one of them - and which one is indeterminate unless you modify the order by - but in that case you might prefer to use first 1 row with ties to see them all.
You could achieve the same thing with a subquery and analytic function to generating a ranking, and have the outer query return the highest-ranking row(s):
select id, numb as maxnumb
from (
select id, numb, dense_rank() over (order by numb desc) as rnk
from table1
)
where rnk = 1
You could also use keep to get the same result as first 1 row only:
select max(id) keep (dense_rank last order by numb) as id, max(numb) as maxnumb
from table1
fiddle
How would I include the name of any one of the books that belong to that particular type in the below query?
select distinct
(select sum(ob.Balance)),
ob.BookType
from orders.OrderBooks ob
group by ob.BookType
In its current state it does what I need it to and groups books by BookType and sums their balances, as seen below.
However I need the name of any book that belongs to that BookType as part of the result.
If I select the BookName column and then group by it like below, it results in more unique entries and to an extent undoes the original grouping.
select distinct
(select sum(ob.Balance)),
ob.BookType,
ob.BookName
from orders.OrderBooks ob
group by ob.BookType, ob.BookName
;WITH x AS
(
SELECT
Balance = SUM(Balance) OVER (PARTITION BY BookType),
BookType,
BookName,
rn = ROW_NUMBER() OVER (PARTITION BY BookType ORDER BY BookName DESC)
FROM orders.OrderBooks
)
SELECT Balance, BookType, BookName
FROM x
WHERE rn = 1;
db<>fiddle
ORDER BY BookName DESC was dealer's choice. If you truly don't care which title shows up in the result, you can use any ordering you like. If you want the results to be random every time, you can use ORDER BY NEWID().
In general I like this flexibility better than the TOP (1) subquery approach, in addition to a single scan instead of an additional table access per row. But you can also do it a different way; just take min/max of the bookname, too:
SELECT Balance = SUM(Balance),
BookType,
BookName = MIN(BookName) -- or MAX()
FROM dbo.OrderBooks
GROUP BY BookType;
You can see these give similar results in this db<>fiddle. Plan is simpler, too; most notably: no spools. However when you use an aggregate function against that column, it makes it harder to provide arbitrary/random results, and if you intend to add other columns pulled from the right row, you'll need to go back to the row_number solution.
You can use a correlated subquery to get a single book name of that type. This assumes there's an ID field and you want to pull the most recent one:
select
Balance = (select sum(ob.Balance)),
ob.BookType,
BookName = (SELECT TOP(1) ob.BookName FROM orders.OrderBooks ob2 WHERE ob2.BookType = ob.BookType ORDER BY ob2.ID DESC)
from orders.OrderBooks ob
group by ob.BookType, ob.BookName
I want to use a query, showing the top two best Quantity. If the table is like the picture, how can the desired result be produced
You can use DENSE_RANK(). For example:
select
id, name, quantity
from (
select
id, name, quantity,
dense_rank() over(order by quantity desc) as rk
from t
) x
where rk <= 2
DENSE_RANK() computes a number for each row according to an ordering of your choosing. Identical values get the same number, and no numbers are skipped. See SQL Fiddle.
You can use the TOP/LIMIT functions in query. Which would allow you to select a specific number of rows.
using number as 5 you can get the desired result from:
SELECT columnname FROM tablename WHERE condition LIMIT number;
or
SELECT TOP (number)/(percent) columnname FROM tablename WHERE condition;
I have the following table:
ItemID Price
1 10
2 20
3 12
4 10
5 11
I need to find the second lowest price. So far, I have a query that works, but i am not sure it is the most efficient query:
select min(price)
from table
where itemid not in
(select itemid
from table
where price=
(select min(price)
from table));
What if I have to find third OR fourth minimum price? I am not even mentioning other attributes and conditions... Is there any more efficient way to do this?
PS: note that minimum is not a unique value. For example, items 1 and 4 are both minimums. Simple ordering won't do.
SELECT MIN( price )
FROM table
WHERE price > ( SELECT MIN( price )
FROM table )
select price from table where price in (
select
distinct price
from
(select t.price,rownumber() over () as rownum from table t) as x
where x.rownum = 2 --or 3, 4, 5, etc
)
Not sure if this would be the fastest, but it would make it easier to select the second, third, etc... Just change the TOP value.
UPDATED
SELECT MIN(price)
FROM table
WHERE price NOT IN (SELECT DISTINCT TOP 1 price FROM table ORDER BY price)
To find out second minimum salary of an employee, you can use following:
select min(salary)
from table
where salary > (select min(salary) from table);
This is a good answer:
SELECT MIN( price )
FROM table
WHERE price > ( SELECT MIN( price )
FROM table )
Make sure when you do this that there is only 1 row in the subquery! (the part in brackets at the end).
For example if you want to use GROUP BY you will have to define even further using:
SELECT MIN( price )
FROM table te1
WHERE price > ( SELECT MIN( price )
FROM table te2 WHERE te1.brand = te2.brand)
GROUP BY brand
Because GROUP BY will give you multiple rows, otherwise you will get the error:
SQL Error [21000]: ERROR: more than one row returned by a subquery used as an expression
I guess a simplest way to do is using offset-fetch filter from standard sql, distinct is not necessary if you don't have repeat values in your column.
select distinct(price) from table
order by price
offset 1 row fetch first 1 row only;
no need to write complex subqueries....
In amazon redshift use limit-fetch instead for ex...
Select distinct(price) from table
order by price
limit 1
offset 1;
You can either use one of the following:-
select min(your_field) from your_table where your_field NOT IN (select distinct TOP 1 your_field from your_table ORDER BY your_field DESC)
OR
select top 1 ColumnName from TableName where ColumnName not in (select top 1 ColumnName from TableName order by ColumnName asc)
I think you can find the second minimum using LIMIT and ORDER BY
select max(price) as minimum from (select distinct(price) from tableName order by price asc limit 2 ) --or 3, 4, 5, etc
if you want to find third or fourth minimum and so on... you can find out by changing minimum number in limit. you can find using this statement.
You can use RANK functions,
it may seem complex query but similar results like other answers can be achieved with the same,
WITH Temp_table AS (SELECT ITEM_ID,PRICE,RANK() OVER (ORDER BY PRICE) AS
Rnk
FROM YOUR_TABLE_NAME)
SELECT ITEM_ID FROM Temp_table
WHERE Rnk=2;
Maybe u can check the min value first and then place a not or greater than the operator. This will eliminate the usage of a subquery but will require a two-step process
select min(price)
from table
where min(price) <> -- "the min price you previously got"
I want to use the ROW_NUMBER() to get...
To get the max(ROW_NUMBER()) --> Or i guess this would also be the count of all rows
I tried doing:
SELECT max(ROW_NUMBER() OVER(ORDER BY UserId)) FROM Users
but it didn't seem to work...
To get ROW_NUMBER() using a given piece of information, ie. if I have a name and I want to know what row the name came from.
I assume it would be something similar to what I tried for #1
SELECT ROW_NUMBER() OVER(ORDER BY UserId) From Users WHERE UserName='Joe'
but this didn't work either...
Any Ideas?
For the first question, why not just use?
SELECT COUNT(*) FROM myTable
to get the count.
And for the second question, the primary key of the row is what should be used to identify a particular row. Don't try and use the row number for that.
If you returned Row_Number() in your main query,
SELECT ROW_NUMBER() OVER (Order by Id) AS RowNumber, Field1, Field2, Field3
FROM User
Then when you want to go 5 rows back then you can take the current row number and use the following query to determine the row with currentrow -5
SELECT us.Id
FROM (SELECT ROW_NUMBER() OVER (ORDER BY id) AS Row, Id
FROM User ) us
WHERE Row = CurrentRow - 5
Though I agree with others that you could use count() to get the total number of rows, here is how you can use the row_count():
To get the total no of rows:
with temp as (
select row_number() over (order by id) as rownum
from table_name
)
select max(rownum) from temp
To get the row numbers where name is Matt:
with temp as (
select name, row_number() over (order by id) as rownum
from table_name
)
select rownum from temp where name like 'Matt'
You can further use min(rownum) or max(rownum) to get the first or last row for Matt respectively.
These were very simple implementations of row_number(). You can use it for more complex grouping. Check out my response on Advanced grouping without using a sub query
If you need to return the table's total row count, you can use an alternative way to the SELECT COUNT(*) statement.
Because SELECT COUNT(*) makes a full table scan to return the row count, it can take very long time for a large table. You can use the sysindexes system table instead in this case. There is a ROWS column that contains the total row count for each table in your database. You can use the following select statement:
SELECT rows FROM sysindexes WHERE id = OBJECT_ID('table_name') AND indid < 2
This will drastically reduce the time your query takes.
You can use this for get first record where has clause
SELECT TOP(1) * , ROW_NUMBER() OVER(ORDER BY UserId) AS rownum
FROM Users
WHERE UserName = 'Joe'
ORDER BY rownum ASC
ROW_NUMBER() returns a unique number for each row starting with 1. You can easily use this by simply writing:
ROW_NUMBER() OVER (ORDER BY 'Column_Name' DESC) as ROW_NUMBER
May not be related to the question here. But I found it could be useful when using ROW_NUMBER -
SELECT *,
ROW_NUMBER() OVER (ORDER BY (SELECT 100)) AS Any_ID
FROM #Any_Table
select
Ml.Hid,
ml.blockid,
row_number() over (partition by ml.blockid order by Ml.Hid desc) as rownumber,
H.HNAME
from MIT_LeadBechmarkHamletwise ML
join [MT.HAMLE] h on ML.Hid=h.HID
SELECT num, UserName FROM
(SELECT UserName, ROW_NUMBER() OVER(ORDER BY UserId) AS num
From Users) AS numbered
WHERE UserName='Joe'
You can use Row_Number for limit query result.
Example:
SELECT * FROM (
select row_number() OVER (order by createtime desc) AS ROWINDEX,*
from TABLENAME ) TB
WHERE TB.ROWINDEX between 0 and 10
--
With above query, I will get PAGE 1 of results from TABLENAME.
If you absolutely want to use ROW_NUMBER for this (instead of count(*)) you can always use:
SELECT TOP 1 ROW_NUMBER() OVER (ORDER BY Id)
FROM USERS
ORDER BY ROW_NUMBER() OVER (ORDER BY Id) DESC
Need to create virtual table by using WITH table AS, which is mention in given Query.
By using this virtual table, you can perform CRUD operation w.r.t row_number.
QUERY:
WITH table AS
-
(SELECT row_number() OVER(ORDER BY UserId) rn, * FROM Users)
-
SELECT * FROM table WHERE UserName='Joe'
-
You can use INSERT, UPDATE or DELETE in last sentence by in spite of SELECT.
SQL Row_Number() function is to sort and assign an order number to data rows in related record set. So it is used to number rows, for example to identify the top 10 rows which have the highest order amount or identify the order of each customer which is the highest amount, etc.
If you want to sort the dataset and number each row by seperating them into categories we use Row_Number() with Partition By clause. For example, sorting orders of each customer within itself where the dataset contains all orders, etc.
SELECT
SalesOrderNumber,
CustomerId,
SubTotal,
ROW_NUMBER() OVER (PARTITION BY CustomerId ORDER BY SubTotal DESC) rn
FROM Sales.SalesOrderHeader
But as I understand you want to calculate the number of rows of grouped by a column. To visualize the requirement, if you want to see the count of all orders of the related customer as a seperate column besides order info, you can use COUNT() aggregation function with Partition By clause
For example,
SELECT
SalesOrderNumber,
CustomerId,
COUNT(*) OVER (PARTITION BY CustomerId) CustomerOrderCount
FROM Sales.SalesOrderHeader
This query:
SELECT ROW_NUMBER() OVER(ORDER BY UserId) From Users WHERE UserName='Joe'
will return all rows where the UserName is 'Joe' UNLESS you have no UserName='Joe'
They will be listed in order of UserID and the row_number field will start with 1 and increment however many rows contain UserName='Joe'
If it does not work for you then your WHERE command has an issue OR there is no UserID in the table. Check spelling for both fields UserID and UserName.