select Top(1)* from TableName Where columnName=value
selects only the first row just fine. However if I change the select to a delete I get an error and can't figure out how to write a query to delete only 1 record that matches my query from the db.
I'm wondering if anybody out there smarter than I knows if or how this can be done in SQL CE.
Did you try something like this?
DELETE TableName where IdColumn In ( select Top(1) IdColumn from TableName Where columnName=valuev)
I don't know specifically as I'm at home, but SQL CE is deliberately restricted in what it can do. One reason for this is that it is 'always' running locally to the process referencing it.
What means is that it is Expected that the other process is expected to handle much of the logic that may otherwise be encapsulated in the SQL Server. This often results in firing several queries at the SQL CE instance, where you may be more accustomed to firing off one.
In this case, you could do it with two queries...
1) A query to identify the record that you want to delete
2) Use that Identifier in another query to do the actual delete
You could also try using SET ROWCOUNT 1 to limit the DELETE to just 1 row. But again, I don't know if that works in CE.
You can use CTE such as
;with myTopRow(rowID)
(
select Top 1 rowID from TableName Where columnName=value
)
delete from TableName inner join myTopRow on TableName.rowID = myTopRow.rowID
Shouldn't it be rather :
DELETE FROM TableName WHERE columnName=value ORDER BY columnName LIMIT 1;
IMHO, the table logically has NO order by itself. It has it physically, but you can't rely on it. So, you HAVE to set the order in which you want to delete the first row.
The following code will delete only first row
Dim mySqlCommondDelete As String = "DELETE BOOK_ID, MemberID FROM (SELECT TOP 1 * FROM ISSUE_BOOK) where BOOK_ID = Val(" & deleteBook & ") and MemberID = Val(" & msk & ")"
Related
I know this is a very basic question but I am unable to get it done. Just started to learn more about databases. I have two tables: tblFoodAllowance and tblTravelDays.
tblFoodAllowance consists of ID, tripID, dateDay, costs.
tblTravelDay saves all days when I was on a business trip: ID, dateDay.
I am looking for a delete query in SQL to use in MS Access which does this: Delete all from tblFoodAllowance where tripID is xy (e.g. 1) and tblFoodAllowance.dateDay is not in the list of tblTravelDates. How can I achieve this?
I tried multiple things but either I got a syntax error or a wrong result. Thanks for your help.
I guess it is something like:
DELETE * FROM tblFoodAllowance WHERE tblFoodAllowance.tripID = [tripID] and ()
You can use delete:
delete from tblFoodAllowance
where tripID = #xy and
not exists (select 1
from tblTravelDates
where tblTravelDates.tripId = tblFoodAllowance.tripId and
tblTravelDates.dateDay = tblFoodAllowance.dateDay
);
Consider using not exists and a correlated subquery. It is a bit unclear exactly which colums connect the two tables, but the idea is:
delete from tblFoodAllowance
where
tripID = 1
and not exists (
select 1
from tblTravelDay
where tblTravelDay.dateDay = tblFoodAllowance.dateDay
)
I'm trying to determine if a table in my SQL Server 2012 database has any records that don't exist in a table that's on a linked Oracle 11g database.
I tried to do this with the following:
select 1
from my_order_table ord
where not exists (select 1
from LINK_ORA..[SCHEMA1].[ORDERS]
where doc_id = ord.document_id)
and document_id = 'N2324JKL3511'
The issue is that it never completes because the ORDERS table on the linked server has about 100 million rows and as per the explain plan on SQL Server, it is trying to pull back the entire ORDERS table from the linked server and then apply the WHERE clause.
As per the explain plan, it views the remote table as having an estimated 10000 rows - I assume that's some kind of default if it is unable to get statistics..?
Even running something as simple as this:
select 1 from LINK_ORA..[SCHEMA1].[ORDERS] where doc_id = 'N2324JKL3511'
causes SQL Server to not send the WHERE clause and the query never completes.
I tried to use OPENQUERY however it won't let me add the doc_id to concatenate into the WHERE clause of the query string.
Then I tried to build a select FROM OPENQUERY string in a function but I can't use sp_executesql in a function to run it.
Any help is greatly appreciated.
I think this would logically work for you, but it may take too long as well.
SELECT sql_ord.*
FROM my_order_table sql_ord
LEFT JOIN LINK_ORA..[SCHEMA1].[ORDERS] ora_ord ON sql_ord.document_id = ora_ord.doc_id
WHERE sql_ord.document_id = 'N2324JKL3511'
AND ora_ord.doc_id IS NULL
Since you have problem with something as simple as select 1 from LINK_ORA..[SCHEMA1].[ORDERS] where doc_id = 'N2324JKL3511' have you try to create a table on the remote server that will hold the doc_id that you want to look at. So your SELECT will include a table that contain only 1 row. I'm just not sure about the INSERT since I can't test it for now. I'm assuming that everything will be done on the remote server.
So something like :
CREATE TABLE LINK_ORA..[SCHEMA1].linked_server_doc_id (
doc_id nvarchar(12));
INSERT INTO LINK_ORA..[SCHEMA1].linked_server_doc_id (doc_id)
SELECT doc_id
FROM LINK_ORA..[SCHEMA1].[ORDERS] WHERE doc_id = 'N2324JKL3511';
select 1
from my_order_table ord
where not exists (select 1
from LINK_ORA..[SCHEMA1].[linked_server_doc_id]
where doc_id = ord.document_id)
and document_id = 'N2324JKL3511';
DROP TABLE LINK_ORA..[SCHEMA1].linked_server_doc_id
Can anyone advise me as to what is wrong with the following SQL server update statement:
IF (SELECT * FROM TBL_SystemParameter WHERE code='SOUND_WRONG_GARMENT') = ''
GO
UPDATE TBL_SystemParameter
SET [Value] = 'Ping.wav'
WHERE ID = (SELECT ID
FROM TBL_SystemParameter
WHERE code = 'SOUND_WRONG_GARMENT')
You don't need an if statement - you can just run the update statement, and if the subquery returns no rows, no rows will be updated. The if won't really save anything - you're performing two queries instead of one.
You either want
UPDATE TBL_SystemParameter
SET [Value] = 'Ping.wav'
WHERE ID In (SELECT ID
FROM TBL_SystemParameter
WHERE code = 'SOUND_WRONG_GARMENT')
if there are multiple ID's with that code OR use
UPDATE TBL_SystemParameter
SET [Value] = 'Ping.wav'
WHERE code = 'SOUND_WRONG_GARMENT'
either way and lose the IF statement as #Mureinik said.
Although Mureinik's answer is the logical solution to this, I will answer why this isn't actually working. Your condition is wrong, and this approach will work instead using IF EXISTS:
IF EXISTS (SELECT * FROM TBL_SystemParameter WHERE code='SOUND_WRONG_GARMENT')
BEGIN
UPDATE TBL_SystemParameter
SET [Value] = 'Ping.wav'
WHERE ID IN (SELECT ID
FROM TBL_SystemParameter
WHERE code = 'SOUND_WRONG_GARMENT')
END
As a side note, you're using an = sign instead of IN, which means you'll be matching to an arbitrary singular ID and only update 1 row based on this. To use a set based operation, use the IN clause.
You could actually 'golf' this by doing away with the derived query altogether, and using a simple WHERE code='SOUND_WRONG_GARMENT' on the table you're updating on.
I am building a SQL Server job to pull data from SQL Server into an Oracle database through a linked server. The table I need to populate has a sequence for the name ID, which is my primary key. I'm having trouble figuring out a way to do this simply, without some lengthy code. Here's what I have so far for the SELECT portion (some actual names obfuscated):
SELECT (SELECT NEXTVAL FROM OPENQUERY(MYSERVER,
'SELECT ORCL.NAME_SEQNO.NEXTVAL FROM DUAL')),
psn.BirthDate, psn.FirstName,
psn.MiddleName, psn.LastName, c.REGION_CODE
FROM Person psn
LEFT JOIN MYSERVER..ORCL.COUNTRY c ON c.COUNTRY_CODE = psn.Country
MYSERVER is the linked Oracle server, ORCL is obviously the schema. Person is a local table on the SQL Server database where the query is being executed.
When I run this query, I get the same exact value for all records for the NEXTVAL. What I need is for it to generate a new value for each returned record.
I found this similar question, with its answers, but am unsure how to apply it to my case (if even possible): Query several NEXTVAL from sequence in one statement
put it in a SQL scalar function. Example:
CREATE function [dbo].SEQ_PERSON()
returns bigint as
begin
return
( select NEXTVAL
from openquery(oraLinkedServer, 'select SEQ_PERSON.NEXTVAL FROM DUAL')
)
end
I ended up having to iterate through all the records and set the ID value individually. Messy and slow, but it seems to be the only option in this scenario.
Very easy Just Use a CURSOR to Iterate with the code :
SELECT NEXTVAL AS SQ from OPENQUERY(MYSERVER, 'SELECT AC2012.NAME_SEQNO.NEXTVAL FROM DUAL')
So you can embed this select statement in any Sql statement, and Iterate by the CURSOR.
PS:
DECLARE SQCURS CURSOR
FOR SELECT (SELECT NEXTVAL AS SQ FROM OPENQUERY(MYSERVER,
'SELECT ORCL.NAME_SEQNO.NEXTVAL FROM DUAL')),
psn.BirthDate, psn.FirstName, psn.MiddleName, psn.LastName, c.REGION_CODE
FROM Person psn
LEFT JOIN MYSERVER..ORCL.COUNTRY c ON c.COUNTRY_CODE = psn.Country
OPEN SQCURS
FETCH NEXT FROM SQCURS ;
I hope that help
I want to check if there are any records in a table for a certain entry. I used COUNT(*) to check the number of records and got it to work. However, when the number of records for an entry is very high, my page loads slowly.
I guess COUNT(*) is causing the problem, but how do I check if the records exist without using it? I only want to check whether any records exist for the entry and then execute some code. Please help me find an alternative solution for this.
Thanks for any help.
There are several ways that may work. You can use exists, which lets the database optimise the method to get the answer:
if exists(select * from ...)
You can use top 1 so that the database can stop after finding the first match:
if (select count(*) from (select top 1 * from ...)) > 0
use select top 1 and check is there is an row
You can try selecting the first entry for given condition.
SELECT id FROM table WHERE <condition> LIMIT 1
I'm not sure if this will be quicker but you can try.
Other possible solution. How do you use count? COUNT(*)? If yes, then try using COUNT(id). As I remember this should be faster.
I would recommend testing to see if at least 1 record exists in the table, that meets your criteria then continue accordingly. For example:
IF EXISTS
(
SELECT TOP 1 Table_Name --Or Your ColumnName
FROM INFORMATION_SCHEMA.Tables -- Or your TableName
)
BEGIN
PRINT 'At least one record exists in table'
END
I found this on codeproject. It's quite handy.
-- Author,,Md. Marufuzzaman
SELECT SYS_OBJ.NAME AS "TABLE NAME"
, SYS_INDX.ROWCNT AS "ROW COUNT"
FROM SYSOBJECTS SYS_OBJ, SYSINDEXES SYS_INDX
WHERE SYS_INDX.ID = SYS_OBJ.ID
AND INDID IN(0,1) --This specifies 'user' databases only
AND XTYPE = 'U' --This omits the diagrams table of the database
--You may find other system tables will need to be ommitted,
AND SYS_OBJ.NAME <> 'SYSDIAGRAMS'
ORDER BY SYS_INDX.rowcnt DESC --I found it more useful to display
--The following line adds up all the rowcount results and places
--the final result into a separate column [below the first resulting table]
COMPUTE SUM(SYS_INDX.ROWCNT)
GO
you should use
select count(1) from
If you are saying (*) it will expand all the column's and then count