Query in sql server? - sql-server

how to replace this query in sql server ?
DELETE FROM student
WHERE id=2
AND list_column_name='lastName'
OR list_column_name='firstName'
LIMIT 3;

There is no ORDER BY in your original query.
If you just want to delete an arbitary three records matching your WHERE you can use.
DELETE TOP(3) FROM student
WHERE id = 2
AND list_column_name = 'lastName'
OR list_column_name = 'firstName';
For greater control of TOP (as ordered by what?) you need to use a CTE or similar.

using CTE and TOP 3 where equal to LIMIT 3
;WITH CTE
AS (SELECT TOP 3 Studentname
FROM student
WHERE id = 2
AND list_column_name = 'lastName'
OR list_column_name = 'firstName')
DELETE FROM CTE

Related

Strange behavior of TOP in subquery with Order By

I am using SQL Server 2014 and trying to get 10th record and wrote following query.
SELECT TOP 1 *
FROM (SELECT TOP 10 * from Books) AS B
ORDER BY ID DESC;
But it returns me the the last record. I figure out that it is using order by ID DESC from outer query.
Few more tries and its results are as below.
Query 1 Its working as expected.
SELECT *
FROM (SELECT TOP 10 * from Books) AS B
Result
Query 2 Its not working as expected. It should be return records with ID from 10-1.
SELECT *
FROM (SELECT TOP 10 * from Books) AS B
ORDER BY ID DESC;
Result
Query 3 If I'm using ORDER BY inside subquery then it's working as expected.
SELECT *
FROM (SELECT TOP 10 * from Books ORDER BY ID ASC) AS B
ORDER BY ID DESC;
Result
Can anyone tell me what I'm doing wrong. Why it is necessary to use ORDER BY inside subquery?
If in Query 1 getting records from ID between 1-10 then why in Query 2 it returns last 10 records? I have just added ORDER BY DESC which should re-order fetched records from subquery only.?
Also tried on W3School Try it yourself link here with following query and its working properly.
SELECT TOP 1 * FROM (SELECT TOP 10 * from Customers) AS B ORDER BY CustomerId DESC;
There's no sort in the subquery.
Try a CTE-
WITH CteBooks as (
SELECT TOP 10 * FROM Books ORDER BY ID ASC
)
SELECT TOP 1 * FROM CteBooks ORDER BY ID DESC;
What about OFFSET clause :
SELECT CustomerID
FROM Customers
ORDER BY CustomerID ASC
OFFSET 10 ROWS
FETCH NEXT 1 ROWS ONLY
Works on SQL Server 2012 and select the element at offset 10 and take only one row.

SQL Join one-to-many tables, selecting only most recent entries

This is my first post - so I apologise if it's in the wrong seciton!
I'm joining two tables with a one-to-many relationship using their respective ID numbers: but I only want to return the most recent record for the joined table and I'm not entirely sure where to even start!
My original code for returning everything is shown below:
SELECT table_DATES.[date-ID], *
FROM table_CORE LEFT JOIN table_DATES ON [table_CORE].[core-ID] = table_DATES.[date-ID]
WHERE table_CORE.[core-ID] Like '*'
ORDER BY [table_CORE].[core-ID], [table_DATES].[iteration];
This returns a group of records: showing every matching ID between table_CORE and table_DATES:
table_CORE date-ID iteration
1 1 1
1 1 2
1 1 3
2 2 1
2 2 2
3 3 1
4 4 1
But I need to return only the date with the maximum value in the "iteration" field as shown below
table_CORE date-ID iteration Additional data
1 1 3 MoreInfo
2 2 2 MoreInfo
3 3 1 MoreInfo
4 4 1 MoreInfo
I really don't even know where to start - obviously it's going to be a JOIN query of some sort - but I'm not sure how to get the subquery to return only the highest iteration for each item in table 2's ID field?
Hope that makes sense - I'll reword if it comes to it!
--edit--
I'm wondering how to integrate that when I'm needing all the fields from table 1 (table_CORE in this case) and all the fields from table2 (table_DATES) joined as well?
Both tables have additional fields that will need to be merged.
I'm pretty sure I can just add the fields into the "SELECT" and "GROUP BY" clauses, but there are around 40 fields altogether (and typing all of them will be tedious!)
Try using the MAX aggregate function like this with a GROUP BY clause.
SELECT
[ID1],
[ID2],
MAX([iteration])
FROM
table_CORE
LEFT JOIN table_DATES
ON [table_CORE].[core-ID] = table_DATES.[date-ID]
WHERE
table_CORE.[core-ID] Like '*' --LIKE '%something%' ??
GROUP BY
[ID1],
[ID2]
Your example field names don't match your sample query so I'm guessing a little bit.
Just to make sure that I have everything you’re asking for right, I am going to restate some of your question and then answer it.
Your source tables look like this:
table_core:
table_dates:
And your outputs are like this:
Current:
Desired:
In order to make that happen all you need to do is use a subquery (or a CTE) as a “cross-reference” table. (I used temp tables to recreate your data example and _ in place of the - in your column names).
--Loading the example data
create table #table_core
(
core_id int not null
)
create table #table_dates
(
date_id int not null
, iteration int not null
, additional_data varchar(25) null
)
insert into #table_core values (1), (2), (3), (4)
insert into #table_dates values (1,1, 'More Info 1'),(1,2, 'More Info 2'),(1,3, 'More Info 3'),(2,1, 'More Info 4'),(2,2, 'More Info 5'),(3,1, 'More Info 6'),(4,1, 'More Info 7')
--select query needed for desired output (using a CTE)
; with iter_max as
(
select td.date_id
, max(td.iteration) as iteration_max
from #table_dates as td
group by td.date_id
)
select tc.*
, td.*
from #table_core as tc
left join iter_max as im on tc.core_id = im.date_id
inner join #table_dates as td on im.date_id = td.date_id
and im.iteration_max = td.iteration
select *
from
(
SELECT table_DATES.[date-ID], *
, row_number() over (partition by table_CORE date-ID order by iteration desc) as rn
FROM table_CORE
LEFT JOIN table_DATES
ON [table_CORE].[core-ID] = table_DATES.[date-ID]
WHERE table_CORE.[core-ID] Like '*'
) tt
where tt.rn = 1
ORDER BY [core-ID]

Create index for huge query in MS SQL Server

I have the following huge request :
SELECT TOP (100000)
B.UserId AS [UserId], B.ProfileId AS [ProfileId]
FROM
tBounce AS B
JOIN
tBounceType AS BT ON BT.Id = B.BounceTypeId
WHERE
BT.IsHard = 1 AND B.IsProcessedByAutoUnsubscriber = 0
GROUP BY
B.UserId, B.ProfileId
HAVING
count(*) > 2
The tBounce table contains billions of records, which columns do I need to include in an index ? Need i add grouping fields as well ?

Anyway to get a value similar to ##ROWCOUNT when TOP is used?

If I have a SQL statement such as:
SELECT TOP 5
*
FROM Person
WHERE Name LIKE 'Sm%'
ORDER BY ID DESC
PRINT ##ROWCOUNT
-- shows '5'
Is there anyway to get a value like ##ROWCOUNT that is the actual count of all of the rows that match the query without re-issuing the query again sans the TOP 5?
The actual problem is a much more complex and intensive query that performs beautifully since we can use TOP n or SET ROWCOUNT n but then we cannot get a total count which is required to display paging information in the UI correctly. Presently we have to re-issue the query with a #Count = COUNT(ID) instead of *.
Whilst this doesn't exactly meet your requirement (in that the total count isn't returned as a variable), it can be done in a single statement:
;WITH rowCTE
AS
(
SELECT *
,ROW_NUMBER() OVER (ORDER BY ID DESC) AS rn1
,ROW_NUMBER() OVER (ORDER BY ID ASC) AS rn2
FROM Person
WHERE Name LIKE 'Sm%'
)
SELECT *
,(rn1 + rn2) - 1 as totalCount
FROM rowCTE
WHERE rn1 <=5
The totalCount column will have the total number of rows matching the where filter.
It would be interesting to see how this stacks up performance-wise against two queries on a decent-sized data-set.
you'll have to run another COUNT() query:
SELECT TOP 5
*
FROM Person
WHERE Name LIKE 'Sm%'
ORDER BY ID DESC
DECLARE #r int
SELECT
#r=COUNT(*)
FROM Person
WHERE Name LIKE 'Sm%'
select #r
Something like this may do it:
SELECT TOP 5
*
FROM Person
cross join (select count(*) HowMany
from Person
WHERE Name LIKE 'Sm%') tot
WHERE Name LIKE 'Sm%'
ORDER BY ID DESC
The subquery returns one row with one column containing the full count; the cross join includes it with all rows returned by the "main" query"; and "SELECT *" would include new column HowMany.
Depending on your needs, the next step might be to filter out that column from your return set. One way would be to load the data from the query into a temp table, and then return just the desired columns, and get rowcount from the HowMany column from any row.

How do I select last 5 rows in a table without sorting?

I want to select the last 5 records from a table in SQL Server without arranging the table in ascending or descending order.
This is just about the most bizarre query I've ever written, but I'm pretty sure it gets the "last 5" rows from a table without ordering:
select *
from issues
where issueid not in (
select top (
(select count(*) from issues) - 5
) issueid
from issues
)
Note that this makes use of SQL Server 2005's ability to pass a value into the "top" clause - it doesn't work on SQL Server 2000.
Suppose you have an index on id, this will be lightning fast:
SELECT * FROM [MyTable] WHERE [id] > (SELECT MAX([id]) - 5 FROM [MyTable])
The way your question is phrased makes it sound like you think you have to physically resort the data in the table in order to get it back in the order you want. If so, this is not the case, the ORDER BY clause exists for this purpose. The physical order in which the records are stored remains unchanged when using ORDER BY. The records are sorted in memory (or in temporary disk space) before they are returned.
Note that the order that records get returned is not guaranteed without using an ORDER BY clause. So, while any of the the suggestions here may work, there is no reason to think they will continue to work, nor can you prove that they work in all cases with your current database. This is by design - I am assuming it is to give the database engine the freedom do as it will with the records in order to obtain best performance in the case where there is no explicit order specified.
Assuming you wanted the last 5 records sorted by the field Name in ascending order, you could do something like this, which should work in either SQL 2000 or 2005:
select Name
from (
select top 5 Name
from MyTable
order by Name desc
) a
order by Name asc
You need to count number of rows inside table ( say we have 12 rows )
then subtract 5 rows from them ( we are now in 7 )
select * where index_column > 7
select * from users
where user_id >
( (select COUNT(*) from users) - 5)
you can order them ASC or DESC
But when using this code
select TOP 5 from users order by user_id DESC
it will not be ordered easily.
select * from table limit 5 offset (select count(*) from table) - 5;
Without an order, this is impossible. What defines the "bottom"? The following will select 5 rows according to how they are stored in the database.
SELECT TOP 5 * FROM [TableName]
Well, the "last five rows" are actually the last five rows depending on your clustered index. Your clustered index, by definition, is the way that he rows are ordered. So you really can't get the "last five rows" without some order. You can, however, get the last five rows as it pertains to the clustered index.
SELECT TOP 5 * FROM MyTable
ORDER BY MyCLusteredIndexColumn1, MyCLusteredIndexColumnq, ..., MyCLusteredIndexColumnN DESC
Search 5 records from last records you can use this,
SELECT *
FROM Table Name
WHERE ID <= IDENT_CURRENT('Table Name')
AND ID >= IDENT_CURRENT('Table Name') - 5
If you know how many rows there will be in total you can use the ROW_NUMBER() function.
Here's an examble from MSDN (http://msdn.microsoft.com/en-us/library/ms186734.aspx)
USE AdventureWorks;
GO
WITH OrderedOrders AS
(
SELECT SalesOrderID, OrderDate,
ROW_NUMBER() OVER (ORDER BY OrderDate) AS 'RowNumber'
FROM Sales.SalesOrderHeader
)
SELECT *
FROM OrderedOrders
WHERE RowNumber BETWEEN 50 AND 60;
In SQL Server 2012 you can do this :
Declare #Count1 int ;
Select #Count1 = Count(*)
FROM [Log] AS L
SELECT
*
FROM [Log] AS L
ORDER BY L.id
OFFSET #Count - 5 ROWS
FETCH NEXT 5 ROWS ONLY;
Try this, if you don't have a primary key or identical column:
select [Stu_Id],[Student_Name] ,[City] ,[Registered],
RowNum = row_number() OVER (ORDER BY (SELECT 0))
from student
ORDER BY RowNum desc
You can retrieve them from memory.
So first you get the rows in a DataSet, and then get the last 5 out of the DataSet.
There is a handy trick that works in some databases for ordering in database order,
SELECT * FROM TableName ORDER BY true
Apparently, this can work in conjunction with any of the other suggestions posted here to leave the results in "order they came out of the database" order, which in some databases, is the order they were last modified in.
select *
from table
order by empno(primary key) desc
fetch first 5 rows only
Last 5 rows retrieve in mysql
This query working perfectly
SELECT * FROM (SELECT * FROM recharge ORDER BY sno DESC LIMIT 5)sub ORDER BY sno ASC
or
select sno from(select sno from recharge order by sno desc limit 5) as t where t.sno order by t.sno asc
When number of rows in table is less than 5 the answers of Matt Hamilton and msuvajac is Incorrect.
Because a TOP N rowcount value may not be negative.
A great example can be found Here.
i am using this code:
select * from tweets where placeID = '$placeID' and id > (
(select count(*) from tweets where placeID = '$placeID')-2)
In SQL Server, it does not seem possible without using ordering in the query.
This is what I have used.
SELECT *
FROM
(
SELECT TOP 5 *
FROM [MyTable]
ORDER BY Id DESC /*Primary Key*/
) AS T
ORDER BY T.Id ASC; /*Primary Key*/
DECLARE #MYVAR NVARCHAR(100)
DECLARE #step int
SET #step = 0;
DECLARE MYTESTCURSOR CURSOR
DYNAMIC
FOR
SELECT col FROM [dbo].[table]
OPEN MYTESTCURSOR
FETCH LAST FROM MYTESTCURSOR INTO #MYVAR
print #MYVAR;
WHILE #step < 10
BEGIN
FETCH PRIOR FROM MYTESTCURSOR INTO #MYVAR
print #MYVAR;
SET #step = #step + 1;
END
CLOSE MYTESTCURSOR
DEALLOCATE MYTESTCURSOR
Thanks to #Apps Tawale , Based on his answer, here's a bit of another (my) version,
To select last 5 records without an identity column,
select top 5 *,
RowNum = row_number() OVER (ORDER BY (SELECT 0))
from [dbo].[ViewEmployeeMaster]
ORDER BY RowNum desc
Nevertheless, it has an order by, but on RowNum :)
Note(1): The above query will reverse the order of what we get when we run the main select query.
So to maintain the order, we can slightly go like:
select *, RowNum2 = row_number() OVER (ORDER BY (SELECT 0))
from (
select top 5 *, RowNum = row_number() OVER (ORDER BY (SELECT 0))
from [dbo].[ViewEmployeeMaster]
ORDER BY RowNum desc
) as t1
order by RowNum2 desc
Note(2): Without an identity column, the query takes a bit of time in case of large data
Get the count of that table
select count(*) from TABLE
select top count * from TABLE where 'primary key row' NOT IN (select top (count-5) 'primary key row' from TABLE)
If you do not want to arrange the table in ascending or descending order. Use this.
select * from table limit 5 offset (select count(*) from table) - 5;

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