I'm new to Oracle and recently ran into the following query. I'm trying to understand what it's doing and hopefully rewrite it to optimize it. In this example, :NameList would be a comma separated list (like: "Bob,Bill,Fred") and then :N_NameList would be the number of tokens (in above example, 3)
SELECT ... FROM
(
SELECT
REGEXP_SUBSTR(:NameList,'[^,]+',1,LEVEL, 'i') Name
FROM DUAL CONNECT BY LEVEL <= :N_NameList
) x
INNER JOIN PEOPLE ppl
ON ppl.Name LIKE x.Name
...
From what I can tell, it expands out the delimited list into unique rows and then joins it with the following tables for each name, but I'm not sure if that's all it's doing. If that is the case, is there a better way to accomplish this?
You could try this instead:
select ...
from people ppl
where instr (','||:NameList||',',
','||ppl.name||',') > 0;
is there a better way to accomplish this?
Well, you could get rid of N_NameList because you can easily count number of tokens. This doesn't mean that it is a better way, it's just a different option. To be honest, it is probably slower option than yours as I have to calculate something that you entered as a parameter.
As this example is based on SQLPlus, I've used & instead of : for substitution variables. && means that it'll "remember" previously entered value (otherwise, I should type NameList twice.
Your current query:
SQL> select regexp_substr('&namelist', '[^,]+', 1, level, 'i') name
2 from dual
3 connect by level <= &n_namelist;
Enter value for namelist: Bob,Bill,Fred
Enter value for n_namelist: 3
Bob
Bill
Fred
Calculated N_NameList (using REGEXP_COUNT):
SQL> select regexp_substr('&&namelist', '[^,]+', 1, level, 'i') name
2 from dual
3 connect by level <= regexp_count('&&namelist', ',') + 1;
Enter value for namelist: Bob,Bill,Fred
Bob
Bill
Fred
Related
I'm wondering if it's possible to pass one or more parameters to a WITH clause query; in a very simple way, doing something like this (taht, obviously, is not working!):
with qq(a) as (
select a+1 as increment
from dual
)
select qq.increment
from qq(10); -- should get 11
Of course, the use I'm going to do is much more complicated, since the with clause should be in a subquery, and the parameter I'd pass are values taken from the main query....details upon request... ;-)
Thanks for any hint
OK.....here's the whole deal:
select appu.* from
(<quite a complex query here>) appu
where not exists
(select 1
from dual
where appu.ORA_APP IN
(select slot from
(select distinct slots.inizio,slots.fine from
(
with
params as (select 1900 fine from dual)
--params as (select app.ora_fine_attivita fine
-- where app.cod_agenda = appu.AGE
-- and app.ora_fine_attivita = appu.fine_fascia
--and app.data_appuntamento = appu.dataapp
--)
,
Intervals (inizio, EDM) as
( select 1700, 20 from dual
union all
select inizio+EDM, EDM from Intervals join params on
(inizio <= fine)
)
select * from Intervals join params on (inizio <= fine)
) slots
) slots
where slots.slot <= slots.fine
)
order by 1,2,3;
Without going in too deep details, the where condition should remove those records where 'appu.ORA_APP' match one of the records that are supposed to be created in the (outer) 'slots' table.
The constants used in the example are good for a subset of records (a single 'appu.AGE' value), that's why I should parametrize it, in order to use the commented 'params' table (to be replicated, then, in the 'Intervals' table.
I know thats not simple to analyze from scratch, but I tried to make it as clear as possible; feel free to ask for a numeric example if needed....
Thanks
I'm struggling with getting a query to work, and I could really use some help. We have an in house app that we use for building small web apps where I work. It's basically a drag and drop GUI. There's functionality built in to access query string values using the key.
I'm passing a comma separated list of values into a page through the query string. I'm then trying to use the list of values as part of an in clause in a query.
I can see that the value is correct in the query string.
orders=1,2,3
Here's the specific part of the query
"AND OrderNumber IN (this is where it maps from the query string)
I've tried running similar queries in Toad, and I think I've found the issue. It's giving an invalid number error, and I think it's wrapping the query string value in single quotes. I can replicate the error when I do "AND OrderNumber IN ('1,2,3')" in Toad.
Here's where I get really confused. The following works in Toad.
"AND OrderNumber IN ('1','2','3')"
So I tried recreating that by doing
select replace('1,2,3', ',', chr(39)||','||chr(39)) from dual;
I have confirmed that returns '1','2','3' in Toad.
However, I still get an Invalid Number error when I run the following in Toad.
AND OrderNumber IN (replace('1,2,3', ',', chr(39)||','||chr(39))
I've been racking my brain over this, and I can't figure it out. It seems to me that if "AND OrderNumber IN ('1','2','3')" works, and replace('1,2,3', ',', chr(39)||','||chr(39)) returns '1','2','3', that "AND OrderNumber IN (replace('1,2,3', ',', chr(39)||','||chr(39))" should work.
Any help you might be able to offer on this would be greatly appreciated. I know the rest of the query works. That's why I didn't post it. I'm just stuck on trying to get this IN clause working.
A change to phonetic_man's answer that will allow for NULL elements in the list. The regex format of '[^,]+' for parsing delimited lists does not handle NULL list elements and will return an incorrect value if one exists and thus its use should be avoided. Change the original by deleting the number 2 for instance and see the results. You will get a '3' in the 2nd element's position! Here's a way that handles the NULL and returns the correct value for the element:
SELECT TRIM(REGEXP_SUBSTR(str, '(.*?)(,|$)', 1, LEVEL, NULL, 1)) str
FROM ( SELECT '1,,3,4' str FROM dual )
connect by level <= regexp_count(str, ',') + 1;
See here for more info and proof: https://stackoverflow.com/a/31464699/2543416
Can you try the following query.
SELECT * FROM orders
WHERE orderno IN
(
SELECT TRIM(REGEXP_SUBSTR(str, '[^,]+', 1, LEVEL)) str
FROM ( SELECT '1,2,3,4' str FROM dual )
CONNECT BY INSTR(str, ',', 1, LEVEL - 1) > 0
)
The inline query splitting the string in different rows. So, on executing it you will get the following result.
SELECT trim(regexp_substr(str, '[^,]+', 1, LEVEL)) str
FROM ( SELECT '1,2,3,4' str FROM dual )
CONNECT BY instr(str, ',', 1, LEVEL - 1) > 0
1
2
3
4
Now, passing this result to the main query IN clause should work.
I think the desired clause to be built is:
AND OrderNumber IN (1,2,3)
A numeric list. The example you tested:
AND OrderNumber IN ('1','2','3')
works because an implicit conversion from a VARCHAR2 to a NUMBER is occurring for each element in the list.
The following clause will not work because no implicit conversion of the string '1,2,3' can be made (note the clause has a single string element):
AND OrderNumber IN ('1,2,3')
When doing a replace, you are converting the single string: 1,2,3 with the single string: 1','2','3 and this single string cannot be implicitly converted to a number.
Firstly, I greatly appreciate any feedback that anyone can offer. I am using Oracle SQL Developer, Version 4.0.2.15, Build 15.21.
I know and understand that many, many similar questions have been asked, as I've searched around on stackoverflow as well as the rest of the internet. However, the corresponding answers are either too vague or too extravagant, and attempt to do things that are way over my head and not what I am trying to accomplish. I am extremely new to SQL and haven't seriously done any coding since I did Java about 12 years ago. So please understand that something simple to you, is not so simple and obvious to me.
My bare-bones endstate that I am shooting for is taking a pre-existing Oracle Table Column, which is called 'service_level', that has parameters of 1-3, and making them A-C (where A=1, B=2, C=3). The reason for this is that I have an ArcGIS gdB featureclass that has a corresponding column, called 'MaintServi', with the parameters of A-C. I am going to join them using ArcToolbox once I have converted/replaced the 1-3 to A-C, and have exported them from Oracle into an Arc gdB as another table. The reason being is that the featureclass (obviously) has geometry, but this particular Oracle table does not.
From what I have gathered I know (or think) I will need to use something like:
chr(ord('a') + 3)
^ Where I will need to use/call upon the chr/ord functions. However, due to my inexperience, I cannot think of how to properly call this without getting an error. Below is what I have for my query thus far (but without chr/ord). I just need to figure out how to correctly insert it into my query to achieve the desired results.
SELECT v_wv_wp_crew.*,
Substr(v_wv_wp_crew.winter_supp_id, 1, 6) AS CostCenter,
Substr(v_wv_wp_crew.winter_supp_id, 8, 11) AS Crew_Supp_ID
FROM v_wv_wp_crew
WHERE crew_on_road >= '13-FEB-12'
AND ( operation = 2
OR operation = 3 );
Thanks again and hopefully I have complied with the posting rules of stackoverflow.
# Mark J. Bobak -
When implementing his ideas I get either this (Like I said, i'm not sure how to insert it properly without receiving an error)
SELECT v_wv_wp_crew.*,
Substr(v_wv_wp_crew.winter_supp_id, 1, 6) AS CostCenter,
Substr(v_wv_wp_crew.winter_supp_id, 8, 11) AS Crew_Supp_ID
FROM v_wv_wp_crew
WHERE crew_on_road >= '13-FEB-12'
AND ( operation = 2
OR operation = 3 )
UNION ALL
WITH service_level as (select 1 service_level from dual
union all
select 2 service_level from dual union all
select 3 service_level from dual)
select decode(service_level,1,'A',2,'B',3,'C') from service_level;
I receive the following error:
*ORA-32034: unsupported use of WITH clause
32034. 00000 - "unsupported use of WITH clause"
*Cause: Inproper use of WITH clause because one of the following two reasons
1. nesting of WITH clause within WITH clause not supported yet
2. For a set query, WITH clause can't be specified for a branch.
3. WITH clause can't sepecified within parentheses.
Action: correct query and retry
Error at Line: 14 Column: 25
Or I receive an output of only 3 rows (A, B, C) if I run the query separately - sorry I don't have enough reputation to post the image yet.
You can use the DECODE() function. Something like this should work:
with list_of_digits as (select 1 col_a from dual
union all
select 2 col_a from dual
union all
select 3 col_a from dual
union all
select 4 col_a from dual)
select decode(col_a,1,'A',2,'B',3,'C','Other') from list_of_digits;
Using your query, try this:
WITH service_level as (select 1 service_level from dual
union all
select 2 service_level from dual union all
select 3 service_level from dual)
select decode(service_level,1,'A',2,'B',3,'C') from service_level
union all
SELECT v_wv_wp_crew.*,
Substr(v_wv_wp_crew.winter_supp_id, 1, 6) AS CostCenter,
Substr(v_wv_wp_crew.winter_supp_id, 8, 11) AS Crew_Supp_ID
FROM v_wv_wp_crew
WHERE crew_on_road >= '13-FEB-12'
AND ( operation = 2
OR operation = 3 );
ord isn't an Oracle function. The equivalent Oracle function is ASCII. However, even substituting in the correct function, I don't see how that gets you what you want.
It seems most likely that you just want to add a column (I'd use case to translate the values):
SELECT v_wv_wp_crew.*,
Substr(v_wv_wp_crew.winter_supp_id, 1, 6) AS CostCenter,
Substr(v_wv_wp_crew.winter_supp_id, 8, 11) AS Crew_Supp_ID,
case service_level
when '1' then 'a'
when '2' then 'b'
when '3' then 'c'
end as service_level_alpha
FROM v_wv_wp_crew
WHERE crew_on_road >= '13-FEB-12'
AND ( operation = 2
OR operation = 3 );
If you want to return this column as service_level, then you'll need to return the full list of columns instead of using the asterisk.
Since this is a straight-forward character swap, you could use translate to really streamline the operation: translate(service_level,'123','abc'). However, I vastly prefer case over either decode or translate for readability
I have a query as below
select substr( 'ORACLE DEVELOPER',level,1 ) ITEM
from dual connect by level <= length('ORACLE DEVELOPER') ;
it returns 'O' as the result.
but if i put this as a subquery in other it is displaying the required output.
query is as below.
select a.ITEM from (select substr( 'ORACLE DEVELOPER',level,1 ) ITEM
from dual connect by level <= length('ORACLE DEVELOPER') ) a
How this CONNECT BY is working in subquery.
I am new to this feature. Can anyone explain this??
CONNECT BY is Oracle SQL syntax for doing hierarchical queries. Some good examples are here.
One of the side effects is that it allows you to query a single data source multiple times, which means that there's a handy trick to generate any number of rows with:
SELECT 1
FROM dual
CONNECT BY LEVEL <= 10;
The above will connect dual back to itself 10 times - the LEVEL pseudocolumn is from the hierarchy; because the CONNECT BY clause doesn't actually refer to any data from the rowsource, it effectively makes dual its own child, grandchild, great-grandchild, etc. until the CONNECT BY clause evaluates to false (in this case, when LEVEL becomes greater than 10).
In your case, you are generating a row for each letter of the string (instead of 10, you are referring to LENGTH('a string'), which is a nice way of getting a query to return one record for each letter in the string. You are then using SUBSTR to pick out the nth letter from the string.
I have a row that is a varchar(50) that has a unique constraint and i would like to get the next unique number for an new insert but with a given prefix.
My rows could look like this:
ID (varchar)
00010001
00010002
00010003
00080001
So if I would like to get the next unqiue number from the prefix "0001" it would be "00010004" but if I would want it for the prefix "0008" it would be "00080002".
There will be more then 1 millon entries in this table. Is there a way with Oracle 11 to perform this kind of operation that is fairly fast?
I know that this setup is totaly insane but this is what I have to work with. I cant create any new tables etc.
You can search for the max value of the specified prefix and increment it:
SQL> WITH DATA AS (
2 SELECT '00010001' id FROM DUAL UNION ALL
3 SELECT '00010002' id FROM DUAL UNION ALL
4 SELECT '00010003' id FROM DUAL UNION ALL
5 SELECT '00080001' id FROM DUAL
6 )
7 SELECT :prefix || to_char(MAX(to_number(substr(id, 5)))+1, 'fm0000') nextval
8 FROM DATA
9 WHERE ID LIKE :prefix || '%';
NEXTVAL
---------
00010004
I'm sure you're aware that this is an inefficient method to generate a primary key. Furthermore it won't play nicely in a multi-user environment and thus won't scale. Concurrent inserts will wait then fail since there is a UNIQUE constraint on the column.
If the prefix is always the same length, you can reduce the workload somewhat: you could create a specialized index that would find the max value in a minimum number of steps:
CREATE INDEX ix_fetch_max ON your_table (substr(id, 1, 4),
substr(id, 5) DESC);
Then the following query could use the index and will stop at the first row retrieved:
SELECT id
FROM (SELECT substr(id, 1, 4) || substr(id, 5) id
FROM your_table
WHERE substr(id, 1, 4) = :prefix
ORDER BY substr(id, 5) DESC)
WHERE rownum = 1
If you need to do simultaneous inserts with the same prefix, I suggest you use DBMS_LOCK to request a lock on the specified newID. If the call fails because someone is already inserting this value, try with newID+1. Although this involves more work than traditional sequence, at least your inserts won't wait on each others (potentially leading to deadlocks).
This is a very unsatisfactory situation for you. As other posters have pointed out - if you don't use sequences then you will almost certainly have concurrency issues. I mentioned in a comment the possibility that you live with big gaps. This is the simplest solution but you will run out of numbers after 9999 inserts.
Perhaps an alternative would be to create a separate sequence for each prefix. This would only really be practical if the number of prefixes is fairly low but it could be done.
ps - your requirement that > 1000000 records should be possible may, in fact, mean you have no choice but to redesign the database.
SELECT to_char(to_number(max(id)) + 1, '00000000')
FROM mytable
WHERE id LIKE '0001%'
SQLFiddle demo here http://sqlfiddle.com/#!4/4f543/5/0