I need to add 'P06' to the case where the subquery is selecting RPCODE. I'm still learning about SQL so I'm still not an expert at subqueries so I'm not exactly sure how to add a value to the statement.
My first solution was just to add OR 'P06' after 'P01', but that doesn't seem right.
CASE WHEN (SELECT RPCODE FROM AGQA.QAB2010
WHERE INDATE || INTIME = ( SELECT MAX(INDATE||INTIME) FROM AGQA.QAB2010 WHERE RTAG IN (SELECT TAG FROM TAGDATA) )
AND RTAG IN (SELECT TAG FROM TAGDATA) ORDER BY RPDATE DESC, SER DESC FETCH FIRST 1 ROW ONLY) = 'P01' THEN 'N' ELSE 'C' END
ELSE 'R' END, 'S' ) AS TTYPE
Right now, when the RPCODE is 'P01', the TTYPE shows as 'N'. I need to add 'P06' so that the TTYPE will show as 'N' for RPCODE 'P06' as well
As Rob Wilson commented...
Change the = 'P01' to IN ('P01', 'P06')
However, while the statement may work for you, performance over a dataset of any decent size is probably going to suck.
The number of sub-select's and fetch first row are red flags to my eye.
With a background in RPG development on Db2 for i, the statement looks like many I've seen from RPG programmers used to working with data 1 record at a time rather than working with sets of data.
But the same "row by agonizing row" (RBAR as coined by Jeff Moden of SqlServerCentral.com) processing can be seen in SQL from developers on any platform and from any background.
Unfortunately, moving to a set base process isn't a quick fix for non-trivial statements. The complete statement and detailed information about the data and the table design is needed.
Related
Im learning how to improve some queries I have, for example I saw that using EXISTS over IN does better, so I did the following modification but im not 100% sure if im getting the same results I expect by using EXISTS, so far it gives me the same results when I execute with different periods but im still doubting, could some one clear for me if it does better performance EXISTS and also if its doing the same?
VARIABLE periodo STRING;
SELECT MO.STRMOVANOMES,
C.STRCLINOMBRE,
MO.STRCLINIT,
MO.STROBLOBLIGSARC,
MO.NUMPROCODIGO,
MO.NUMMOVTIPOCREDITO,
MO.NUMMOVTIPOGARANTIA,
MO.STROBLMODALIDAD,
MO.NUMMOVCALIFICACION,
MO.NUMMOVVLRCAPCREDITO,
MO.NUMMOVVLRINTCREDI,
MO.NUMMOVVLRCAPOTRO
FROM TBLMOVOBLIGACIONES MO,
TBLCLIENTES C
WHERE MO.STRMOVANOMES = :periodo
AND C.STRCLITIPOID ='N'
AND MO.NUMMOVTIPOCREDITO = 2
AND MO.NUMPROCODIGO IN (1,3,4,5,6,7,10,15,16,18,24,29,32,38,40,43,44,45,49,51,54,55,56,70,71,72,73,74,75,76,77,78,81,82,83,84,85)--ALL APPLICATIONS
AND C.STRCLINIT=MO.STRCLINIT
AND SUBSTR(MO.STRCLINIT,1,9) >= 600000000
AND SUBSTR(MO.STRCLINIT,1,9) <= 999999999;
-- USING EXISTS
SELECT MO.STRMOVANOMES,
C.STRCLINOMBRE,
MO.STRCLINIT,
MO.STROBLOBLIGSARC,
MO.NUMPROCODIGO,
MO.NUMMOVTIPOCREDITO,
MO.NUMMOVTIPOGARANTIA,
MO.STROBLMODALIDAD,
MO.NUMMOVCALIFICACION,
MO.NUMMOVVLRCAPCREDITO,
MO.NUMMOVVLRINTCREDI,
MO.NUMMOVVLRCAPOTRO
FROM TBLMOVOBLIGACIONES MO,
TBLCLIENTES C
WHERE MO.STRMOVANOMES = :periodo
AND C.STRCLITIPOID ='N'
AND MO.NUMMOVTIPOCREDITO = 2
AND EXISTS (SELECT NUMPROCODIGO FROM TBLMOVOBLIGACIONES)--ALL APPLICATIONS
AND C.STRCLINIT=MO.STRCLINIT
AND SUBSTR(MO.STRCLINIT,1,9) >= 600000000
AND SUBSTR(MO.STRCLINIT,1,9) <= 999999999;
First, some general info
In theory, the IN clause is to be used when there is a need to check some value against a list of values, so the DB has to loop through the list looking for a value given. Whereas EXIST is to let db to perform a quick query (which is db designed for) in order to check if there is at least one row.
If the values list you're checking against is in a table, it is better to use EXISTS in general. That was some theory.
In practice though, starting from version 10 (which is very old one) Oracle builds same exec plans for IN and EXISTS queries, here is a good explanation if you need some more experienced guy.
To check whether it affects query execution, check explain plans (google for it for your dev-tool) and compare overall "costs" (cost comparison it's not always a good thing to relay on, it is okay for such case though)
Now, back to your query.
The EXISTS in the way you are using it will always return true whenever table TBLMOVOBLIGACIONES has at least one row. Not sure this is what you were looking for.
I believe you need to use it somehow in this manner
AND EXISTS (SELECT 1 FROM TBLMOVOBLIGACIONES WHERE NUMPROCODIGO = MO.NUMPROCODIGO)
Thus it will check whether there is at least one record connected to the data you selected on previous step.
Next step I see here is the EXISTS clause can be easily converted to a regular table join, so instead of choosing between IN or EXISTS you might write the following
FROM TBLMOVOBLIGACIONES MO,
TBLCLIENTES C,
TBLMOVOBLIGACIONES M
WHERE MO.STRMOVANOMES = :periodo
AND C.STRCLITIPOID ='N'
AND MO.NUMMOVTIPOCREDITO = 2
AND M.NUMPROCODIGO = MO.NUMPROCODIGO--ALL APPLICATIONS
AND C.STRCLINIT=MO.STRCLINIT
AND SUBSTR(MO.STRCLINIT,1,9) >= 600000000
AND SUBSTR(MO.STRCLINIT,1,9) <= 999999999;
It is worth doing because joins are always better option allowing database to vary table joins ordering to achieve better performance.
I have the following query that is part of a common table expression. I don't understand the function of the "Select -1" statement. It is obviously different than the "Select 1" that is used in "EXISTS" statements. Any ideas?
select days_old,
count(express_cd),
count(*),
case
when round(count(express_cd)*100.0/count(*),2) < 1 then '0'
else ''
end ||
cast(decimal(round(count(express_cd)*100.0/count(*),2),5,2) as varchar(7)) ||
'%'
from foo.bar
group by days_old
union all
select -1, -- Selecting the -1 here
count(express_cd),
count(*),
case
when round(count(express_cd)*100.0/count(*),2) < 1 then '0'
else ''
end ||
cast(decimal(round(count(express_cd)*100.0/count(*),2),5,2) as varchar(7)) ||
'%'
from foo.bar
where days_old between 1 and 7
It's just selecting the number "minus one" for each row returned, just like "select 1" will select the number "one" for each row returned.
There is nothing special about the "select 1" syntax uses in EXISTS statements by the way; it's just selecting some random value because EXISTS requires a record to be returned and a record needs data; the number 1 is sufficient.
Why you would do this, I have no idea.
When you have a union statement, each part of the union must contain the same columns. From what I read when I look at this, the first statement is giving you one line for each days old value and then some stats for each day old. The second part of the union is giving you a summary of all the records that are only a week or so less. Since days old column is not relevant here, they put in a fake value as a placeholder in order to do the union. OF course this is just a guess based on reading thousands of queries through the years. To be sure, I would need to actually run teh code.
Since you say this is a CTE, to really understand why this is is happening, you may need to look at the data it generates and how that data is used in the next query that uses the CTE. That might answer your question.
What you have asked is basically about a business rule unique to your company. The true answer should lie in any requirements documents for the original creation of the code. You should go look for them and read them. We can make guesses based on our own experience but only people in your company can answer the why question here.
If you can't find the documentation, then you need to talk (Yes directly talk, preferably in person) to the Stakeholders who use the data and find out what their needs were. Only do this after running the code and analyzing the results to better understand the meaning of the data returned.
Based on your query, all the records with days_old between 1 and 7 will be output as '-1', that is what select -1 does, nothing special here and there is no difference between select -1 and select 1 in exists, both will output the records as either 1 or -1, they are doing the same thing to check whether if there has any data.
Back to your query, I noticed that you have a union all and compare each four columns you select connected by union all, I am guessing your task is to get a final result with days_old not between 1 and 7 and combine the result with day_old, which is one because you take all between 1 and 7.
It is just a grouping logic there.
Your query returns aggregated
data (counts and rounds) grouped by days_old column plus one more group for data where days_old between 1 and 7.
So, -1 is just another additional group there, it cannot be 1 because days_old=1 is an another valid group.
result will be like this:
row1: days_old=1 count(*)=2 ...
row2: days_old=3 count(*)=5 ...
row3: days_old=9 count(*)=6 ...
row4: days_old=-1 count(*)=7
I am using sql server 2008 r2 and I have two database, which is one have 11.000 record and another is just 3000 record, when i do run this query
SELECT Right(rtrim(tbltransac.No_Faktur),6) as NoUrut,
tbltransac.No_Faktur,
tbltransac.No_FakturP,
tbltransac.Kd_Plg,
Tblcust.Nm_Plg,
GRANDTOTAL AS Total_Faktur,
tbltransac.Nm_Pajak,
tbltransac.Tgl_Faktur,
tbltransac.Tgl_FakturP,
tbltransac.Total_Distribusi
FROM Tblcust
INNER JOIN ViewGrandtotal AS tbltransac ON Tblcust.Kd_Plg = tbltransac.Kd_Plg
WHERE tbltransac.Kd_Trn = 'J'
and year(tbltransac.tgl_faktur)=2015
And ISNULL(tbltransac.No_OPJ,'') <> 'SHOP'
Order by Right(rtrim(tbltransac.No_Faktur),6) Desc
It takes me 1 minute 30 sec in my server (I query it using sql management tool) that have 3000 record but it only took 3 sec to do a query in my another server which is have 11000 record, whats wring with my database?
I've already tried to backup and restore my 3000 record database and restore it in my 11000 record server, it's faster.. took 30 sec to do a query, but it's still annoying if i compare to my 11000 record server. They are in the same spec
How this happend? what i should check? i check on event viewer, resource monitor or sql management log, i couldn't find any error or blocked connection. There is no wrong routing too..
Please help... It just happen a week ago, before this it was fine, and I haven't touch the server more than a month...
as already mentioned before, you have three issues in your query.
Just as an example, change the query to this one:
SELECT Right(rtrim(tbltransac.No_Faktur),6) as NoUrut,
tbltransac.No_Faktur,
tbltransac.No_FakturP,
tbltransac.Kd_Plg,
Tblcust.Nm_Plg,
GRANDTOTAL AS Total_Faktur,
tbltransac.Nm_Pajak,
tbltransac.Tgl_Faktur,
tbltransac.Tgl_FakturP,
tbltransac.Total_Distribusi
FROM Tblcust
INNER JOIN ViewGrandtotal AS tbltransac ON Tblcust.Kd_Plg = tbltransac.Kd_Plg
WHERE tbltransac.Kd_Trn = 'J'
and tbltransac.tgl_faktur BETWEEN '20150101' AND '20151231'
And tbltransac.No_OPJ <> 'SHOP'
Order by NoUrut Desc --Only if you need a sorted output in the datalayer
Another idea, if your viewGrandTotal is quite large, could be an pre-filtering of this table before you join it. Sometimes SQL Server doesn't get a good plan which needs some lovely touch to get him in the right direction.
Maybe this one:
SELECT Right(rtrim(vgt.No_Faktur),6) as NoUrut,
vgt.No_Faktur,
vgt.No_FakturP,
vgt.Kd_Plg,
tc.Nm_Plg,
vgt.Total_Faktur,
vgt.Nm_Pajak,
vgt.Tgl_Faktur,
vgt.Tgl_FakturP,
vgt.Total_Distribusi
FROM (SELECT Kd_Plg, Nm_Plg FROM Tblcust GROUP BY Kd_Plg, Nm_Plg) as tc -- Pre-Filter on just the needed columns and distinctive.
INNER JOIN (
-- Pre filter viewGrandTotal
SELECT DISTINCT vgt.No_Faktur, vgt.No_Faktur, vgt.No_FakturP, vgt.Kd_Plg, vgt.GRANDTOTAL AS Total_Faktur, vgt.Nm_Pajak,
vgt.Tgl_Faktur, vgt.Tgl_FakturP, vgt.Total_Distribusi
FROM ViewGrandtotal AS vgt
WHERE tbltransac.Kd_Trn = 'J'
and tbltransac.tgl_faktur BETWEEN '20150101' AND '20151231'
And tbltransac.No_OPJ <> 'SHOP'
) as vgt
ON tc.Kd_Plg = vgt.Kd_Plg
Order by NoUrut Desc --Only if you need a sorted output in the datalayer
The pre filtering could increase the generation of a better plan.
Another issue could be just the multi-threading. Maybe your query get a parallel plan as it reaches the cost threshold because of the 11.000 rows. The other query just hits a normal plan due to his lower rows. You can take a look at the generated plans by including the actual execution plan inside your SSMS Query.
Maybe you can compare those plans to get a clue. If this doesn't help, you can post them here to get some feedback from me.
I hope this helps. Not quite easy to give you good hints without knowing table structures, table sizes, performance counters, etc. :-)
Best regards,
Ionic
Note: first of all you should avoid any function in Where clause like this one
year(tbltransac.tgl_faktur)=2015
Here Aaron Bertrand how to work with date in Where clause
"In order to make best possible use of indexes, and to avoid capturing too few or too many rows, the best possible way to achieve the above query is ":
SELECT COUNT(*)
FROM dbo.SomeLogTable
WHERE DateColumn >= '20091011'
AND DateColumn < '20091012';
And i cant understand your logic in this piece of code but this is bad part of your query too
ISNULL(tbltransac.No_OPJ,'') <> 'SHOP'
Actually Null <> "Shop" in this case, so Why are you replace it to ""?
Thanks and good luck
Here is some recommendations:
year(tbltransac.tgl_faktur)=2015 replace this with tbltransac.tgl_faktur >= '20150101' and tbltransac.tgl_faktur < '20160101'
ISNULL(tbltransac.No_OPJ,'') <> 'SHOP' replace this with tbltransac.No_OPJ <> 'SHOP' because NULL <> 'SHOP'.
Order by Right(rtrim(tbltransac.No_Faktur),6) Desc remove this, because ordering should be done in presentation layer rather then in data layer.
Read about SARG arguments and predicates:
What makes a SQL statement sargable?
To write an appropriate SARG, you must ensure that a column that has
an index on it appears in the predicate alone, not as a function
parameter. SARGs must take the form of column inclusive_operator
or inclusive_operator column. The column name is alone
on one side of the expression, and the constant or calculated value
appears on the other side. Inclusive operators include the operators
=, >, <, =>, <=, BETWEEN, and LIKE. However, the LIKE operator is inclusive only if you do not use a wildcard % or _ at the beginning of
the string you are comparing the column to
I have the following FireBird query:
update hrs h
set h.plan_week_id=
(select first 1 c.plan_week_id from calendar c
where c.calendar_id=h.calendar_id)
where coalesce(h.calendar_id,0) <> 0
(Intention: For records in hrs with a (non-zero) calendar_id
take calendar.plan_week_id and put it in hrs.plan_week_id)
The trick to select the first record in Oracle is to use WHERE ROWNUM=1, and if understand correctly I do not have to use ROWNUM in a separate outer query because I 'only' match ROWNUM=1 - thanks SO for suggesting Questions that may already have your answer ;-)
This would make it
update hrs h
set h.plan_week_id=
(select c.plan_week_id from calendar c
where (c.calendar_id=h.calendar_id) and (rownum=1))
where coalesce(h.calendar_id,0) <> 0
I'm actually using the 'first record' together with the selection of only one field to guarantee that I get one value back which can be put into h.plan_week_id.
Question: Will the above query work under Oracle as intended?
Right now, I do not have a filled Oracle DB at hand to run the query on.
Like Nicholas Krasnov said, you can test it in SQL Fiddle.
But if you ever find yourself about to use where rownum = 1 in a subquery, alarm bells should go off, because in 90% of the cases you are doing something wrong. Very rarely will you need a random value. Only when all selected values are the same, a rownum = 1 is valid.
In this case I expect calendar_id to be a primary key in calendar. Therefor each record in hrs can only have 1 plan_week_id selected per record. So the where rownum = 1 is not required.
And to answer your question: Yes, it will run just fine. Though the brackets around each where clause are also not required and in fact only confusing (me).
I am selecting from a database of news articles, and I'd prefer to do it all in one query if possible. In the results, I need a sorting criteria that applies ONLY to the first result.
In my case, the first result must have an image, but the others should be sorted without caring about their image status.
Is this something I can do with some sort of conditionals or user variables in a MySQL query?
Even if you manage to find a query that looks like one query, it is going to be logicaly two queries. Have a look at MySQL UNION if you really must make it one query (but it will still be 2 logical queries). You can union the image in the first with a limit of 1 and the rest in the second.
Something like this ensures an article with an image on the top.
SELECT
id,
title,
newsdate,
article
FROM
news
ORDER BY
CASE WHEN HasImage = 'Y' THEN 0 ELSE 1 END,
newsdate DESC
Unless you define "the first result" closer, of course. This query prefers articles with images, articles without will appear at the end.
Another variant (thanks to le dorfier, who deleted his answer for some reason) would be this:
SELECT
id,
title,
newsdate,
article
FROM
news
ORDER BY
CASE WHEN id = (
SELECT MIN(id) FROM news WHERE HasImage = 'Y'
) THEN 0 ELSE 1 END,
newsdate DESC
This sorts the earliest (assuming MIN(id) means "earliest") article with an image to the top.
I don't think it's possible, as it's effectively 2 queries (the first query the table has to get sorted for, and the second unordered), so you might as well use 2 queries with a LIMIT 1 in the first.