I want to copy a subtree e.g.
into the same table, at the next free most-right spot (in this case at /5/...).
Is there any stored procedure which may help me do this? If not: how would I do it?
I'm relatively new to SQL so any help will be appreciated.
Those values look like hierarchyid values which makes this fairly easy. Here's what I came up with:
declare #foo table (
h hierarchyid
);
insert into #foo (h)
values
('/4/1/'),
('/4/1/1/'),
('/4/1/1/6/'),
('/4/1/1/7/');
select h.ToString(),
h.GetReparentedValue('/4/', '/5/').ToString()
from #foo;
The first two statements are just setup (which, incidentally, will make future questions you ask here more likely to be answered if you provide it yourself!). The last bit shows moving the subtree to a new parent.
To avoid having to hard-code the /5/, I came up with this (based on the same setup as above):
declare #root hierarchyid = '/';
select #root.GetDescendant(
max(h).GetAncestor(
max(h).GetLevel()-1),
NULL
).ToString()
from #foo;
This is an informed guess as I don't know your actual data. But that should get you a long way there.
Lastly, to actually change your data to reflect the values that I'm selecting, you'll have to run an update statement. I'll leave that to you.
Related
I am trying to create function which can replace certain words with hyperlink in sql. When I call the function as query in sql, its takes a really long time to execute the query, more than 2-3min. I assumed this is because, the tag_libary table has around 600,000 records and iterating through large number, would consume a lot of processing time.
CREATE FUNCTION dbo.ReplaceTags(#body VARCHAR(MAX))
RETURNS VARCHAR(MAX)
AS
BEGIN
SELECT #body = REPLACE(#body,name,''+name+'')
FROM Tag_Library
RETURN #body
END
article table (id, title, body)
1, Story1, At the same time there is a list consisting of: DUCHS, EUROC, GLSPE and WODST. Only two of the tags have covered with the prices in the last three months - GROSV at 99.11 on 8 October and JUBIL at 0s on 11 September.
tag_library table (id, name)
1,DRYDN33
2,DUCHS
3,DRYDN33
4,DRYDN15
5,EUROC
6,DRYDN15
7,GROSV
Hence, I am writing to seek some advice, if there is a way to make this sql function optimal or would it be better to change this function, into a insert trigger?
Please advice, if possible.
Yust a thought, I did not test it:
Change your query to this one:
SELECT
#body = REPLACE(#body,name,''+name+'')
FROM
Tag_Library
WHERE
#body LIKE '%' + name + '%'
This should filter the Tag_Library table to those records which are present in the input string and the SQL Server do not have to process lots of unnecessary records (replaces). BUT It will not prevent to do a full table / index scan to check the table!
You can improve this solution by storing the required tags in a table per articles (and update that table via triggers when the source records/tables are changed). In this case you can use joins to filter the Tag_Library table (instead of the LIKE operator), but it reqires extra codes to maintain the dictionary.
You're focusing on the wrong thing. The problem is that this is a scalar function, and they perform miserably. You should change it to a table-valued function that returns a single row and use APPLY.
See, for example:
http://dataeducation.com/scalar-functions-inlining-and-performance-an-entertaining-title-for-a-boring-post/
Everywhere I look I see that in order to loop through results you have to use a cursor and in the same post someone saying cursors are bad don't use them (which has always been my philosophy) but now I am stuck. I need to loop through a result set!
Here's the situation. I need to come up with a list of ProductIDs that have 2 different statuses set to a specific value. I start the stored procedure, run the query that finds my products that meet the criteria.
So, now I have a list of ProductIDs that I need to run through my validation process:
16050
16052
41817
48255
Now I need for each of those products (there may be 1 there may be 1000, i don't know) to check a whole list of conditions:
Is a specific field = 'SIMPLE'? if so, perform a bunch of other queries and make sure everything is good
If it is not 'SIMPLE' then run a whole other set of queries and make sure that information is all good.
Is another field = 'YES'? if so, perform a bunch of other queries, if it is not, then do other queries.
Is a cursor what I need to use? Is there some other way to do what I need that I just am not seeing?
Thanks,
Leslie
I ended up using a WHILE loop that I can pass each ProductID into a series of checks!!
declare #counter int
declare #productKey varchar(20)
SET #counter = (select COUNT(*) from ##Magento)
while (1=1)
begin
SET #productKey = (select top 1 ProductKey from ##Magento)
print #productKey;
delete from ##Magento Where ProductKey = #productKey
SET #counter-=1;
IF (#counter=0) BREAK;
end
go
It's hard to say without knowing the specifics of your process, but one approach is to create a function that performs your logic and call that.
eg:
delete from yourtable
where productid in (select ProductID from FilteredProducts)
and dbo.ShouldBeDeletedFunction(ProductID) = 1
In general, cursors are bad, but there are always exceptions. Try to avoid them by thinking in terms of sets, rather than the attributes of an individual record.
I remember reading a while back that randomly SQL Server can slow down and / or take a stupidly long time to execute a stored procedure when it is written like:
CREATE PROCEDURE spMyExampleProc
(
#myParameterINT
)
AS
BEGIN
SELECT something FROM myTable WHERE myColumn = #myParameter
END
The way to fix this error is to do this:
CREATE PROCEDURE spMyExampleProc
(
#myParameterINT
)
AS
BEGIN
DECLARE #newParameter INT
SET #newParameter = #myParameter
SELECT something FROM myTable WHERE myColumn = #newParameter
END
Now my question is firstly is it bad practice to follow the second example for all my stored procedures? This seems like a bug that could be easily prevented with little work, but would there be any drawbacks to doing this and if so why?
When I read about this the problem was that the same proc would take varying times to execute depending on the value in the parameter, if anyone can tell me what this problem is called / why it occurs I would be really grateful, I cant seem to find the link to the post anywhere and it seems like a problem that could occur for our company.
The problem is "parameter sniffing" (SO Search)
The pattern with #newParameter is called "parameter masking" (also SO Search)
You could always use the this masking pattern but it isn't always needed. For example, a simple select by unique key, with no child tables or other filters should behave as expected every time.
Since SQL Server 2008, you can also use the OPTIMISE FOR UNKNOWN (SO). Also see Alternative to using local variables in a where clause and Experience with when to use OPTIMIZE FOR UNKNOWN
I'm trying to figure out if this is relatively well-performing T-SQL (this is SQL Server 2008). I need to create a stored procedure that updates a table. The proc accepts as many parameters as there are columns in the table, and with the exception of the PK column, they all default to NULL. The body of the procedure looks like this:
CREATE PROCEDURE proc_repo_update
#object_id bigint
,#object_name varchar(50) = NULL
,#object_type char(2) = NULL
,#object_weight int = NULL
,#owner_id int = NULL
-- ...etc
AS
BEGIN
update
object_repo
set
object_name = ISNULL(#object_name, object_name)
,object_type = ISNULL(#object_type, object_type)
,object_weight = ISNULL(#object_weight, object_weight)
,owner_id = ISNULL(#owner_id, owner_id)
-- ...etc
where
object_id = #object_id
return ##ROWCOUNT
END
So basically:
Update a column only if its corresponding parameter was provided, and leave the rest alone.
This works well enough, but as the ISNULL call will return the value of the column if the received parameter was null, will SQL Server optimize this somehow? This might be a performance bottleneck on the application where the table might be updated heavily (insertion will be uncommon so the performance there is not a problem). So I'm trying to figure out what's the best way to do this. Is there a way to condition the column expressions with something like CASE WHEN or something? The table will be indexed up the wazoo as well for read performance. Is this the best approach? My alternative at this point is to create the UPDATE expression in code (e.g. inline SQL) and execute it against the server. This would solve my doubts about performance, but I'd rather leave this in a stored proc if possible.
Take a look at Hugo Kornelis' blog post at http://sqlblog.com/blogs/hugo_kornelis/archive/2007/09/30/what-if-null-if-null-is-null-null-null-is-null.aspx. Scoll down a bit to the discussion on COALESCE vs. ISNULL. If portability is a future consideration, look at COALESCE.
However, from a performance perspective, take a look at Adam's performance-centric blog post at http://sqlblog.com/blogs/adam_machanic/archive/2006/07/12/performance-isnull-vs-coalesce.aspx. ISNULL is the speedier.
Your choice...
BTW, I have a bunch of SP's that are just like your example and have no performance issues using ISNULL. (Being a bit lazy, I like to type 6 vs. 8 chars and being a littel prone to finger-dyslexia, ISNULL is much easier to type :-) )
ISNULL is the fastest way- the only way you'll improve is if you pass in NULL or the actual value, and do the ISNULL in the application.
Some how some records in my table are getting updated with value of xyz in a certain column. Out of hundred of stored procedures, functions, triggers, how can I determine which code is doing this action. Is there a way to search through the database some how through each and every script of the code?
Please help.
One approach is to check syscomments
Contains entries for each view, rule,
default, trigger, CHECK constraint,
DEFAULT constraint, and stored
procedure within the database. The
text column contains the original SQL
definition statements..
e.g. select text from syscomments
If you are having trouble finding that literal string, the values could be coming from a table, or they could be being concatenated within a routine.
Try this
Select text from syscomments
where CharIndex('x', text) > 0
and CharIndex('y', text) > 0
and CharIndex('z', text) > 0
That might help you either find the right routine, or further indicate that the values are coming from a table.
This is going to be nearly impossible to do in SQL Server 2000 because the update might very well be from a variable that has that value or a join to another table that has that value and not hard-coded into the stored proc, trigger etc. The update could also be coming from a DTS package, a job, a piece of dynamic code run by the app or even from query analyzer, so the code itself may not be recorded inthe datbase anywhere.
Perhaps a better approach might be to create an audit table for the table in question and have it record the user and the code from the spid that generated the change as well as the old and new values. You'll have to wait until it happens again, but then you would know exactly what changed the value and what value to put it back to if need be.
Alternatively you could run profiler on the system until it happens but profiler tends to hurt performance and is not usually a good idea to run on a production system. If it is happening very often, it might be an acceptable alternative.
Here's a hint as to how you might get some of the info you want for the eventual trigger code you write:
create table #temp (eventtype nvarchar (1000), parameters int, eventinfo nvarchar (4000), myspid int)
declare #myspid int
select #myspid =##spid
insert #temp (eventtype,parameters, eventinfo)
exec ('dbcc inputbuffer (##spid)')
update #temp
set myspid = #myspid
select hostname, program_name, eventinfo
from #temp t
join sysprocesses s on t.myspid = s.spid
WHERE spid = #myspid
You might use sql-profiler to trac the update of a given table / column.