I've been reading around that nested views can be quite inefficient because:
a) Using views in general involves some overheads (getting info from system tables etc.)
b) The optimiser doesn't do anything intelligent with them but just mixes all the joins from each of the nested views into one big, nasty join
If the only way to get the results I need involves writing this "big, nasty" join anyway, does it matter that I'm not putting it directly into a single view, but breaking it into components so that I can also access parts of the join for other purposes?
If the queries process lots of data, are the system overheads really that noticeable?
I'm reading a book 'Professional SQL Server 2000 Programming' by RobertVieirathere is a recommendation: "stay away from building views based onviews"Why? What's so wrong with nested views?
Hi, I have a question about nested views. Is there a way for the view not to place any locks on the underlying tables? I tried to re-write my views and its nested views with "with (nolock)" but when I view the enterprise manager, I still see exclusive and share lock on the tables. Any help would be appreciated. Thanks.
I am working in a project where the business model is complex enoughthat many common retrieval functions become difficult to develop andmaintain in single query statements or functions.I have found the logic is easier to implement (and later modify whenthe code is no longer freshly remembered), by implementing theprocessing layers in nested views, and functions that callsub-functions (UDFs), not too unlike object based programming ornon-DBMS procedural languages. In some cases, the views and functionsare nested three deep.So far, from a design standpoint, this practice is working very well.Code that would be a recusive mess is reduced to two or three simplercode blocks. With the proper indexing and query structure, performanceseems to be satisfactory (time will tell).In MS SQL Server, is there anything which makes this practice unsound?Examples:CREATE VIEW vw2 AS SELECT * FROM tbl1 WHERE ...CREATE VIEW vw3 AS SELECT * FROM vw2 WHERE ...Application uses: SELECT * FROM vw3-or-CREATE FUNCTION udf2 AS SELECT * FROM tbl1 WHERE ...CREATE FUNCTION udf3 AS SELECT * FROM udf2 WHERE ...Application uses: SELECT udf3(param) AS value
The code below is from a nested view, which I've read should be avoided. I've also noticed GETDATE() is used, which I believe causes GETDATE() to be executed for every record selected (correct me if I'm wrong). I'm also guessing a JOIN containing a UNION against a SELECT statement is not a good idea. What other problems do you notice?
SELECT trans.Entry_Code, trans.D_C, trans.ADP_Security_# , trans.TRID, trans.Batch_Code, trans.Last_Money, null as Shares, Settle_date as Process_Date, null as Closing_Price, trans.Dwnld_Date, trans.Acnt, null as Mktval, cast(Null as varchar(20)) as Cusip_#, ACT.dbo.account.account_key AS account_key FROM (SELECT * FROM ADPDBBOOK.dbo.YTD05B WHERE (DATEDIFF(mm, Process_Date, GETDATE()) <= 15) UNION SELECT * FROM ADPDBBOOK.dbo.YTD06B) trans INNER JOIN ACT_DATA.dbo.account ON ACT_DATA.dbo.account.account_key = RIGHT(trans.Acnt, 5) INNER JOIN tbl_Accounts_TransactionalData ON trans.Acnt = tbl_Accounts_TransactionalData.Acnt
Fellow database developers,I would like to draw on your experience with views. I have a databasethat includes many views. Sometimes, views contains other views, andthose views in turn may contain views. In fact, I have some views inmy database that are a product of nested views of up to 6 levels deep!The reason we did this was.1. Object-oriented in nature. Makes it easy to work with them.2. Changing an underlying view (adding new fields, removing etc),automatically the higher up views inherit this new information. Thismake maintenance very easy.3. These nested views are only ever used for the reporting side of ourapplication, not for the day-to-day database use by the application.We use Crystal Reports and Crystal is smart enough (can't believe Ijust said that about Crystal) to only pull back the fields that arebeing accessed by the report. In other words, Crystal will issue aSelect field1, field2, field3 from ReportingView Where .... eventhough "ReportingView" contains a long list of fields.Problems I can see.1. Parent views generally use "Select * From childview". This meansthat we have to execute a "sp_refreshview" command against all viewswhenever child views are altered.2. Parent views return a lot of information that isn't necessarilyused.3. Makes it harder to track down exactly where the information iscoming from. You have to drill right through to the child view to seethe raw table joins etc.Does anyone have any comments on this database design? I would love tohear your opinions and tales from the trenches.Best regards,Rod.
Newbie here. I've only been using SQL for about a year now and have some minor questions about sql objects that reference other objects.
We have some views which reference other views in the joins. I will call one the primary view and the one being referenced in the joins as the secondary view.
Recently we made changes to the secondary view.
After which the primary views which referenced it would not work because of this change and had to be 'refreshed' by using drop/create scripts which essentially just dropped it and recreated the exact same view. I do not recall the exact error message that was returned other than it seemed to suggest that it could no longer see the secondary view since it had been changed. Nothing in the primary view was changed in any way, just the secondary.
Some here where I work have suggested off hand that this was a recompile of the primary view because the contents of the secondary changed.
My questions are:
1. Exactly why did this happen and is there a proper name for it when it does?
2. The same problem does not seem to occur when we have stored procedures referencing views in the joins which had just been changed. Why is that?
Thanks for any help on the matter. I greatly appreciate it.
Hello There,I'm trying to create a view that has calculations dependent oncalculations, where the problem resides is that each time I make acalculation I must create an intermediate view so I can reference aprevious calculation.for example lets say I have my_table that has columns a & b. now I wanta view that has a & b, c = a + b, and d = c + 1.this is grossly simplified, the calculations I actually use are fairlycomplex and copying / pasting them is out of the question.so what I have is my_view_a which makes column c, and my my_view_finalwhich makes column d (however, in my real application I have 5 of theseviews, a/b/c/d/e/)is there anyway I can consolidate all these views into one? I wasthinking of using a stored procedure with temp tables or somethingalong those lines.I just which I can use the aliases that I create for c in d in onestep.any insight would be greatly appreciated.
Can you give a whole SQL statement an alias so you can use it later?
Eg.
SELECT * FROM Employees WHERE age < 19 -- Could I call the above statement something like 'statement1' to use below as shown
SELECT * FROM Employees WHERE age < 25 AND NOT IN (statement1)
Soin effect I get a nested statement. The reason I am asking about aliases is because this would need to be repeated for, E.g. age < 30 Then age < 35 and so on and so forth.
So basically, I just want to alias a qhole SQL statement
Hi all,I have a query that looks like so:SELECT GLDCT AS [Doc Type], GLDOC AS DocNumber, GLALID ASPerson_NameFROM F0911WHERE (GLAID = '00181913')However by stipulating that GLAID = GLAID I cannot get the person_nameas not all the GLALID fields are filled in. from my reading of thehelpdesk I have a felling that a nested query might be the way to goor a self-join but beyond this I am lost!?Many thanks for any pointers in advance.Sam
I am trying to do some nested IF ELSE conditions. I get an error saying 'Error near work Begin'. Below is teh query and the variables comes in thru cursor.
Can somebody advise me on this and also let me know the best practices and alternative to this if any.
IF (@CCTable = 'Claiminassoc') BEGIN IF ( @ClaimCenterField = 'ClaimID' AND @VALUE ='Claim') BEGIN UPDATE dbo.Table SET ColName = 'Y' WHERE ID = @ID AND CCTable = 'Claiminassoc' AND CCField = 'ClaimID' AND DWField = 'CatastropheDesignationFlag' END END
ELSE IF (@CCTable = 'EmploymentData') BEGIN IF (@VALUE ='TRUE') BEGIN UPDATE dbo.Table SET ColName = 'Y' WHERE ID = @ID AND CCTable = 'Claim' AND CCField = 'WagePaymentCont' END
ELSE IF (@VALUE ='FALSE') BEGIN UPDATE dbo.Table SET ColName = 'N' WHERE ID = @ID AND CCTable = 'Claim' AND CCField = 'WagePaymentCont' END END
I have a challenge, which seems like it is probably trivial, but SQL chops are not up to the task, and I am hoping one of you hot-shot DBAs can throw me a bone!
I have a query that populates an OLAP Time dimension table (basically one row per day of the year over several years). What I want to do is expand that table to include each hour of each day over the time span.
The CTE I am using for the day population is:
Code Snippet WITH dates(date) -- A recursive CTE that produce all dates between 2006 and 2057-12-31 AS ( SELECT cast('2006' AS dateTime) date -- SQL Server supports the ISO 8601 format so this is an unambigious shortcut for 1999-01-01 UNION ALL -- http://msdn2.microsoft.com/en-us/library/ms190977.aspx SELECT (date + 1) AS date FROM dates WHERE date < cast('2058' AS dateTime) -1 )
What I wanted to do was something like:
Code Snippet WITH hours(hr) AS ( SELECT (DATEPART(hh,date) hr UNION ALL SELECT (hr + 1) AS hr FROM hours WHERE hr < 24 )
inserted just after
Code Snippet FROM dates
in the initial CTE. But from what I have read, it seems as though nested CTEs are not allowed.
Can someone pls advise the maximum number of nested IIF statements allowed in a VS 2005 report builder layout textbox expression? I seem to be hitting a wall at about 10, but cannot find verification. In case the limitation is by characters, the full expression would run about 3,500. Any other limitations which may have a bearing?
Hi all! I have a problem with my stored procedure, What I'm trying to do here is whenever a user tries to register, the stored procedure will check if the username already exists, and if not it'll now check if the email has already been entered into the database then if not the stored procedure will go ahead and insert the values into the database. *If the username already exists it'll return -1, and if the email already exists then return -2.
SELECT Username FROM UserAccount WHERE Username = @UsernameIF @@ROWCOUNT = 0 SELECT Email FROM UserAccount WHERE Email = @Email IF @@ROWCOUNT = 0 BEGIN
INSERT INTO UserAccount (Username, Password, Email, FirstName, LastName, Gender, BirthDate, Country, State, Zip, AdditionalInfo) VALUES (@Username, @Password, @Email, @FirstName, @LastName, @Gender, @BirthDate, @Country, @State, @Zip, @AdditionalInfo) END ELSE BEGIN
Hi, I'm not sure if this is a good place to ask sql questions, so please bear with me here...I have a table like soid, parentidWhat I'm trying to do is to write a self join where given a random ID, it'll give me the whole tree of its decendents. (I don't need its parent)so say I have data liek soid parentid1 null2 13 2when I specificy 1, it'll give me 2 and 3, even though 3 is indirectly related to 1. when I say 2, it'll just give me 3. Thanks a lot. GREATLY appreicate it.
What's worng, please help? SELECT TTarea,personel,Date FROM person_table WHERE TTarea = (SELECT TTarea FROM TTarea_table WHERE Center='CENTER_office') I have many TTarea and I want to send back from inner SELECT statement but give an error that inner select statement don't return many result.I want to return many result and I display many TTarea in the CENTER_office
Im inserting some data into a table and grabbing the new UserID with this statement
SELECT @UserID = @@IDENTITY
I would like to use the @UserID to Execute another SP within the same proc.. ..something like this
Exec AnotherSP(@UserId)
But this doesnt seem to be working....Its seems to me that this is a much better approach performance wise rather than returning the UserID to the Business Logic Layer and calling another SP....Im I correct in that assumption....any assistance would be greatly appreciated.
I think I am getting an endless loop here... anyone know how to fix it?
***********************
CREATE PROCEDURE TrigSendPreNewIMAlertP2 @REID int
AS
Declare @RRID int Declare @ITID int Declare @FS2 int Declare @FS1 int
Declare crReqRec cursor for select RRID from RequestRecords where REID = @REID and RRSTatus = 'IA' and APID is not null open crReqRec fetch next from crReqRec into @RRID
Declare crImpGrp cursor for select ITID from RequestRecords where RRID = @RRID open crImpGrp fetch next from crImgGrp into @ITID
while @@fetch_status = 0 select @FS1 = @@Fetch_Status
EXEC TrigSendNewIMAlertP2 @ITID
FETCH NEXT FROM crImpGrp into @ITID
close crImpGrp deallocate crImpGrp
while @@Fetch_Status = 0 select @FS2 = @@Fetch_Status
Hi, Although I am quite familiar with MS Access-grade SQL, I am struggling a bit with proper grown up SQL Server. My usual approach to counting things in Access is to first create a query with the conditions on the data, then use this as the basis of a second query that does the actual counting of the presorted data. I believe the way to do this in SQL server is to use a nested query. I want to generate the top 10 highest counts for each pesticide detected (detection is level>0) for a client between two dates. Currently I am using <code> SELECT top 10 Count(Pesticide) AS CountOfPesticide, Pesticide FROM (SELECT tblData.Pesticide, tblData.Level, tblData.Clast, tblData.Client FROM tblData WHERE (((tblData.Day>@sdate) AND (tblData.Day<@edate))) and (tbldata.level>0) and (tbldata.clast=@clast) and (tbldata.client=@client)) as monkeyboy GROUP BY Pesticide ORDER BY Count(Pesticide) ASC" </code> The results that the above SQL turns out though are not reliable. For example, if I set the dates to now and 14 days ago, it produces higher counts for some pesticides then if I set the dates to now and 30 days ago. Any pointers or general advice about nested sql is gratefully accepted! thanks Mike
Hi,Please can somone help me with a nested SQL query. I have two tables please see belowTable 1CallIDEmployeeIDCallSummaryCallStatusTable 2CallHistoryIDCallIDDataAddedCallActionI would like to return the CallID, EmployeeID, CallSummary and CallStatus from Table 1, and also display the last CallAction from Table 2.This is a helpdesk database so a Call will have many CallActions i.e. Open, Held, Assigned Internal. How do I return the last CallAction Added against the selected CallID, I know I use the DateAdded but not sure about nested statements.The results I would like to return to the user would look like this:-Call ID: 1EmployeeID: 1Call Sumary: SQL ProblemCall Status: OpenCall Action (Last Action): Assigned Internal.
-- declare cursor to return the from lat and lon for all segments that do not have address point 109. DECLARE c1 CURSOR FOR (SELECT From_Latitude, From_Longitude, id AS segment_id FROM Segments WHERE SegmentType != 109) OPEN c1 FETCH NEXT FROM c1 INTO @fLat, @fLon, @segId WHILE @@FETCH_STATUS = 0 BEGIN -- insert into table the segId, from lat, from lon and returned segment id from function. INSERT INTO test VALUES (@segId,@fLat,@fLon,dbo.points_test(@fLat,@fLon))
FETCH NEXT FROM c1 INTO @fLat, @fLon, @segId END
CLOSE c1 DEALLOCATE c1
As you can see here I am using a Cursor, which in turn calls a function with each row that is processed in the recordset. The function that is called is as follows...
ALTER FUNCTION points_test(@x INTEGER, @y INTEGER) RETURNS INTEGER AS BEGIN -- function to find the closed segment point with address point 109 to the segment specified in procedure. DECLARE @tempDistance FLOAT(4) SET @tempDistance = 1000000 DECLARE @id, @seg, lat, lon INTEGER DECLARE @distance, @xd, @yd FLOAT DECLARE c1 CURSOR FOR (SELECT from_latitude, from_longitude, id FROM segments WHERE segmenttype = 109) OPEN c1 FETCH NEXT FROM c1 INTO @lat, @lon, @id WHILE @@FETCH_STATUS = 0 BEGIN -- calucations to get distance. SET @xd = (@lat-@x) SET @yd = (@lon-@y) SET @distance = SQRT((@xd*@xd) + (@yd*@yd))
-- test if you have shortest distance. IF (@distance < @tempDistance) BEGIN SET @tempDistance = @distance SET @seg = @id END FETCH NEXT FROM c1 INTO @lat,@lon, @id END CLOSE c1; DEALLOCATE c1; RETURN @seg END
(This function works out an equation to get the shortest distance from two parameters passed to the function calculated with data from each row returned within the cursor) As you can see here, this function contains ANOTHER cursor!! Ouch. The fact that their is an SQL query in a function is a killer, but having another embedded cursor there is also a killer - this has virtually killer the application.
So, how best is it for me to correct this. Should I turn the function into a stored procudure? But even if I do this, the nested cursor still remains. I was thinking maybe to have the SQRT equations within the SELECT expression and then wrapped in a MIN() to maybe get the lowest value.
I have a question why does not the following nested transaction work?
begin tran insert into t1 values('A') begin tran insert into t2 values('1') commit insert into t3 values('B') begin tran insert into t2 values('2') commit rollback
I have a situation where I have two cursors: outer_cursor and inner_cursor. The inner_cursor is supposed to execute based on a value passed on from outer_cursor. It is not running as desired. At runtime, it complians that the inner_cursor is not open.
I want to write one query which will select multiple distinct records from one table For e:g Lets say in a table i have 3 fields name,tel_no,sex Now i want to list all the records which are distinct in each of these fields like distinct name,distinct address
Struggling with how to implement the following psuedo-code in SQL server 2000. ** Can you use more than one CURSOR variable? If yes, when use FETCH_STATUS is it for cur1 or cur2 ??
Sample data is at the bottom. Thanks for ANY suggestions !!
** Assume TABLE 1 is sorted by Record_Type, Order_no, Order_line_no
************************************************** *** dim @rectyp dim @ord# dim @lin#
Fetch (?) 1st record in TABLE1 While Still Records in TABLE1 Set sub_line# = 0 set @rectyp = Record_Type, set @ord# = Order_no, set @lin# = Order_line_no
while @rectyp = Record_Type and @ord# = Order_no and @lin# = Order_line_no Set sub_line# = sub_line# + 1 update TABLE1 set line_ctr = sub_line# get next record end inner WHILE
end outer WHILE
************************************************** **************************** Sample data : Data as it currently exists: Record_type ......Order No......Order line no ......Line Ctr OP.....................458001................5.... ...............0 OP .....................458001..............5 .................. 0 OP..................... 458001..............5..................0 OP .....................458001..............5........ ..........0 OP.....................458191..............1 ..................0 OP.....................458191..............1 .................. 0 OP..................... 458308..............73..................0 OP .....................458308..............73....... ........... 0 OP.....................458308..............73..... .............0 OP.....................458308..............73..... .............0
Want data to look like this after executing code: Record_type ......Order No......Order line no ......Line Ctr OP.....................458001................5.... ...............1 OP .....................458001..............5 .................. 2 OP..................... 458001..............5..................3 OP .....................458001..............5........ ..........4 OP.....................458191..............1 ..................1 OP.....................458191..............1 .................. 2 OP..................... 458308..............73..................1 OP .....................458308..............73....... ........... 2 OP.....................458308..............73..... .............3 OP.....................458308..............73..... .............4
SELECT case when tab1.col2=tab1.col3 and tab1.col3!=0 then (SELECT tab3.col3 FROM tab3) else (case when tab5.col2=tab5.col6 then (SELECT tab7.col1 FROM tab7) else (case when tab1.col2=tab1.col3 then tab1.col4+7 end) end as value From tab5, tab1 WHERE tab1.col1=tab5.col1
I get the error as- Server: Msg 156, Level 15, State 1, Line 6 Incorrect syntax near the keyword 'as'. please help me.
ID | NUMBER | DSTART | DEND | ADDRESS | ---------------------------------------------------------------- 1 | 9524123 | 12 Dec 95 | 24 Dec 95 | London | 2 | 9524123 | 06 Jan 96 | 15 Jan 96 | Paris | 3 | 084521 | 12 Mar 96 | 15 May 96 | New York | 4 | 084521 | 22 Aug 96 | 25 Aug 96 | Sidney | ---------------------------------------------------------------
Now, I need to build a query to show only the latest DTSTART date for each NUMBER. The result would be something like this:
PHP Code:
ID | NUMBER | DSTART | DEND | ADDRESS | ---------------------------------------------------------------- 2 | 9524123 | 06 Jan 96 | 15 Jan 96 | Paris | 4 | 084521 | 22 Aug 96 | 25 Aug 96 | Sidney | ---------------------------------------------------------------
Can you guys help me to build the queries? Thanks in advance.
