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Am trying to list top 3 records from atable based on some amount stored in a column FTE_TMUSD which is of varchar datatype
below is the query i tried
SELECT *FROM
(
SELECT * FROM FSE_TM_ENTRY
ORDER BY FTE_TMUSD desc
)
WHERE rownum <= 3
ORDER BY FTE_TMUSD DESC ;
o/p i got
972,9680,963 -->FTE_TMUSD values which are not displayed in desc
I am expecting an o/p which will display the top 3 records of values
That should work; inline view is ordered by FTE_TMUSD in descending order, and you're selecting values from it.
What looks suspicious are values you specified as the result. It appears that FTE_TMUSD's datatype is VARCHAR2 (ah, yes - it is, you said so). It means that values are sorted as strings, not numbers - and it seems that you expect numbers. So, apply TO_NUMBER to that column. Note that it'll fail if column contains anything but numbers (for example, if there's a value 972C).
Also, an alternative to your query might be use of analytic functions, such as row_number:
with temp as
(select f.*,
row_number() over (order by to_number(f.fte_tmusd) desc) rn
from fse_tm_entry f
)
select *
from temp
where rn <= 3;
I am trying to find out the no. of bookings from a table where customer from City = Liverpool; but it seems to give me wrong results. What could have gone wrong?
Tables : scustom,
sbook.
Data : ABCtable type scustom,
BKcnt(4) type N.
Clear BKcnt.
Select * from scustom into ABCtable where city = 'Liverpool'.
Select * from sbook.
BKcnt = BKcnt + 1.
Endselect.
Write: / ABCtable-id,
15 ABCtable-name,
50 BKcnt.
ENDSELECT.
For "What could have gone wrong", see the diagnosis of #knut : You get the same number for each customer, since you always select the complete sbook table.
For questions like this, it is better to leave the aggregation, grouping etc. to the database. Try this version:
report zz_count_sbook.
parameters: p_city type scustom-city lower case default 'Liverpool'.
data: id type scustom-id,
name type scustom-name,
count type i.
select customid name count(*) into (id,name,count)
from scustom as c
join sbook as b
on b~customid = c~id
where city eq p_city
group by customid name.
write: / id,
15 name,
50 count.
endselect.
Your Select * from sbook. doesn't contain any additional condition. So you count in each loop all entries in sbook, not only the one connected to your entry in scustom.
I don't know tables, so I can't give you the correct select.
You count is not efficient, you don't need to count yourself:
Tables : scustom,
sbook.
Data : ABCtable type scustom,
BKcnt(4) type N.
Clear BKcnt.
Select * from scustom into ABCtable where city = 'Liverpool'.
Select count(*) into BKcnt from sbook
where <???> = ABCtable-<???>. "I don't know your keys, replace <???> with the correct fields.
Write: / ABCtable-id,
15 ABCtable-name,
50 BKcnt.
ENDSELECT.
(I hope my select count is correct. Please check it with the syntax checker. At least there is an aggregation function in ABAP!)
Always use FOR ALL ENTRIES to join two tables for better performance.
SELECT * FROM scustom INTO TABLE ABCtable WHERE city = 'Liverpool'
SELECT count(*) INTO BKcnt FROM sbook FOR ALL ENTRIES IN ABCtable
WHERE <???> = ABCtable-<???>
I need to select rows randomly from an Oracle DB.
Ex: Assume a table with 100 rows, how I can randomly return 20 of those records from the entire 100 rows.
SELECT *
FROM (
SELECT *
FROM table
ORDER BY DBMS_RANDOM.RANDOM)
WHERE rownum < 21;
SAMPLE() is not guaranteed to give you exactly 20 rows, but might be suitable (and may perform significantly better than a full query + sort-by-random for large tables):
SELECT *
FROM table SAMPLE(20);
Note: the 20 here is an approximate percentage, not the number of rows desired. In this case, since you have 100 rows, to get approximately 20 rows you ask for a 20% sample.
SELECT * FROM table SAMPLE(10) WHERE ROWNUM <= 20;
This is more efficient as it doesn't need to sort the Table.
SELECT column FROM
( SELECT column, dbms_random.value FROM table ORDER BY 2 )
where rownum <= 20;
In summary, two ways were introduced
1) using order by DBMS_RANDOM.VALUE clause
2) using sample([%]) function
The first way has advantage in 'CORRECTNESS' which means you will never fail get result if it actually exists, while in the second way you may get no result even though it has cases satisfying the query condition since information is reduced during sampling.
The second way has advantage in 'EFFICIENT' which mean you will get result faster and give light load to your database.
I was given an warning from DBA that my query using the first way gives loads to the database
You can choose one of two ways according to your interest!
In case of huge tables standard way with sorting by dbms_random.value is not effective because you need to scan whole table and dbms_random.value is pretty slow function and requires context switches. For such cases, there are 3 additional methods:
1: Use sample clause:
https://docs.oracle.com/en/database/oracle/oracle-database/19/sqlrf/SELECT.html#GUID-CFA006CA-6FF1-4972-821E-6996142A51C6
https://docs.oracle.com/en/database/oracle/oracle-database/19/sqlrf/SELECT.html#GUID-CFA006CA-6FF1-4972-821E-6996142A51C6
for example:
select *
from s1 sample block(1)
order by dbms_random.value
fetch first 1 rows only
ie get 1% of all blocks, then sort them randomly and return just 1 row.
2: if you have an index/primary key on the column with normal distribution, you can get min and max values, get random value in this range and get first row with a value greater or equal than that randomly generated value.
Example:
--big table with 1 mln rows with primary key on ID with normal distribution:
Create table s1(id primary key,padding) as
select level, rpad('x',100,'x')
from dual
connect by level<=1e6;
select *
from s1
where id>=(select
dbms_random.value(
(select min(id) from s1),
(select max(id) from s1)
)
from dual)
order by id
fetch first 1 rows only;
3: get random table block, generate rowid and get row from the table by this rowid:
select *
from s1
where rowid = (
select
DBMS_ROWID.ROWID_CREATE (
1,
objd,
file#,
block#,
1)
from
(
select/*+ rule */ file#,block#,objd
from v$bh b
where b.objd in (select o.data_object_id from user_objects o where object_name='S1' /* table_name */)
order by dbms_random.value
fetch first 1 rows only
)
);
To randomly select 20 rows I think you'd be better off selecting the lot of them randomly ordered and selecting the first 20 of that set.
Something like:
Select *
from (select *
from table
order by dbms_random.value) -- you can also use DBMS_RANDOM.RANDOM
where rownum < 21;
Best used for small tables to avoid selecting large chunks of data only to discard most of it.
Here's how to pick a random sample out of each group:
SELECT GROUPING_COLUMN,
MIN (COLUMN_NAME) KEEP (DENSE_RANK FIRST ORDER BY DBMS_RANDOM.VALUE)
AS RANDOM_SAMPLE
FROM TABLE_NAME
GROUP BY GROUPING_COLUMN
ORDER BY GROUPING_COLUMN;
I'm not sure how efficient it is, but if you have a lot of categories and sub-categories, this seems to do the job nicely.
-- Q. How to find Random 50% records from table ?
when we want percent wise randomly data
SELECT *
FROM (
SELECT *
FROM table_name
ORDER BY DBMS_RANDOM.RANDOM)
WHERE rownum <= (select count(*) from table_name) * 50/100;
I have 60,000 records in the dbf file in FoxPro. I want to split it into each 20,000 records (20000 * 3 = 60,000).
How can I achieve this?
I am new to FoxPro. I am using Visual FoxPro 5.0.
Thanks in advance.
You must issue a SKIP command when using the COPY command to make sure you are starting on the next record.
USE MyTable
GO TOP
COPY NEXT 20000 TO NewTable1
SKIP 1
COPY NEXT 20000 TO NewTable2
SKIP 1
COPY NEXT 20000 TO NewTable3
Todd's suggestion will work if you don't care how the records are split. If you want to divide them up based on their content, you'll want to do something like Stuart's first suggestion, though his exact answer will only work if the IDs for the records run from 1 to 60,000 in order.
What's the ultimate goal here? Why divide the table up?
Tamar
You can directly select from the first table:
SELECT * from MyBigTable INTO TABLE SmallTable1 WHERE ID < 20000
SELECT * from MyBigTable INTO TABLE SmallTable2 WHERE ID BETWEEN (20000, 39999)
SELECT * from MyBigTable INTO TABLE SmallTable3 WHERE ID > 39999
if you want more control, though, or you need to manipulate the data, you can use xbase code, something like this:
SELECT MyBigTable
scan
scatter name oRecord memo
if oRecord.Id < 20000
select SmallTable1
append blank
gather name oRecord memo
else if oRecord.Id < 40000
select SmallTable2
append blank
gather name oRecord memo
else
select SmallTable3
append blank
gather name oRecord memo
endscan
It's been a while since I used VFP and I don't have it here, so apologies for any syntax errors.
use in 0 YourTable
select YourTable
go top
copy to NewTable1 next 20000
copy to NewTable2 next 20000
copy to NewTable3 next 20000
If you wanted to split based on record numbers, try this:
SELECT * FROM table INTO TABLE tbl1 WHERE RECNO() <= 20000
SELECT * FROM table INTO TABLE tbl2 WHERE BETWEEN(RECNO(), 20001, 40000)
SELECT * FROM table INTO TABLE tbl3 WHERE RECNO() > 40000
This question already has answers here:
SQL IN Clause 1000 item limit
(5 answers)
Closed 8 years ago.
Is there any way to get around the Oracle 10g limitation of 1000 items in a static IN clause? I have a comma delimited list of many of IDs that I want to use in an IN clause, Sometimes this list can exceed 1000 items, at which point Oracle throws an error. The query is similar to this...
select * from table1 where ID in (1,2,3,4,...,1001,1002,...)
Put the values in a temporary table and then do a select where id in (select id from temptable)
select column_X, ... from my_table
where ('magic', column_X ) in (
('magic', 1),
('magic', 2),
('magic', 3),
('magic', 4),
...
('magic', 99999)
) ...
I am almost sure you can split values across multiple INs using OR:
select * from table1 where ID in (1,2,3,4,...,1000) or
ID in (1001,1002,...,2000)
You may try to use the following form:
select * from table1 where ID in (1,2,3,4,...,1000)
union all
select * from table1 where ID in (1001,1002,...)
Where do you get the list of ids from in the first place? Since they are IDs in your database, did they come from some previous query?
When I have seen this in the past it has been because:-
a reference table is missing and the correct way would be to add the new table, put an attribute on that table and join to it
a list of ids is extracted from the database, and then used in a subsequent SQL statement (perhaps later or on another server or whatever). In this case, the answer is to never extract it from the database. Either store in a temporary table or just write one query.
I think there may be better ways to rework this code that just getting this SQL statement to work. If you provide more details you might get some ideas.
Use ...from table(... :
create or replace type numbertype
as object
(nr number(20,10) )
/
create or replace type number_table
as table of numbertype
/
create or replace procedure tableselect
( p_numbers in number_table
, p_ref_result out sys_refcursor)
is
begin
open p_ref_result for
select *
from employees , (select /*+ cardinality(tab 10) */ tab.nr from table(p_numbers) tab) tbnrs
where id = tbnrs.nr;
end;
/
This is one of the rare cases where you need a hint, else Oracle will not use the index on column id. One of the advantages of this approach is that Oracle doesn't need to hard parse the query again and again. Using a temporary table is most of the times slower.
edit 1 simplified the procedure (thanks to jimmyorr) + example
create or replace procedure tableselect
( p_numbers in number_table
, p_ref_result out sys_refcursor)
is
begin
open p_ref_result for
select /*+ cardinality(tab 10) */ emp.*
from employees emp
, table(p_numbers) tab
where tab.nr = id;
end;
/
Example:
set serveroutput on
create table employees ( id number(10),name varchar2(100));
insert into employees values (3,'Raymond');
insert into employees values (4,'Hans');
commit;
declare
l_number number_table := number_table();
l_sys_refcursor sys_refcursor;
l_employee employees%rowtype;
begin
l_number.extend;
l_number(1) := numbertype(3);
l_number.extend;
l_number(2) := numbertype(4);
tableselect(l_number, l_sys_refcursor);
loop
fetch l_sys_refcursor into l_employee;
exit when l_sys_refcursor%notfound;
dbms_output.put_line(l_employee.name);
end loop;
close l_sys_refcursor;
end;
/
This will output:
Raymond
Hans
I wound up here looking for a solution as well.
Depending on the high-end number of items you need to query against, and assuming your items are unique, you could split your query into batches queries of 1000 items, and combine the results on your end instead (pseudocode here):
//remove dupes
items = items.RemoveDuplicates();
//how to break the items into 1000 item batches
batches = new batch list;
batch = new batch;
for (int i = 0; i < items.Count; i++)
{
if (batch.Count == 1000)
{
batches.Add(batch);
batch.Clear()
}
batch.Add(items[i]);
if (i == items.Count - 1)
{
//add the final batch (it has < 1000 items).
batches.Add(batch);
}
}
// now go query the db for each batch
results = new results;
foreach(batch in batches)
{
results.Add(query(batch));
}
This may be a good trade-off in the scenario where you don't typically have over 1000 items - as having over 1000 items would be your "high end" edge-case scenario. For example, in the event that you have 1500 items, two queries of (1000, 500) wouldn't be so bad. This also assumes that each query isn't particularly expensive in of its own right.
This wouldn't be appropriate if your typical number of expected items got to be much larger - say, in the 100000 range - requiring 100 queries. If so, then you should probably look more seriously into using the global temporary tables solution provided above as the most "correct" solution. Furthermore, if your items are not unique, you would need to resolve duplicate results in your batches as well.
Yes, very weird situation for oracle.
if you specify 2000 ids inside the IN clause, it will fail.
this fails:
select ...
where id in (1,2,....2000)
but if you simply put the 2000 ids in another table (temp table for example), it will works
below query:
select ...
where id in (select userId
from temptable_with_2000_ids )
what you can do, actually could split the records into a lot of 1000 records and execute them group by group.
Here is some Perl code that tries to work around the limit by creating an inline view and then selecting from it. The statement text is compressed by using rows of twelve items each instead of selecting each item from DUAL individually, then uncompressed by unioning together all columns. UNION or UNION ALL in decompression should make no difference here as it all goes inside an IN which will impose uniqueness before joining against it anyway, but in the compression, UNION ALL is used to prevent a lot of unnecessary comparing. As the data I'm filtering on are all whole numbers, quoting is not an issue.
#
# generate the innards of an IN expression with more than a thousand items
#
use English '-no_match_vars';
sub big_IN_list{
#_ < 13 and return join ', ',#_;
my $padding_required = (12 - (#_ % 12)) % 12;
# get first dozen and make length of #_ an even multiple of 12
my ($a,$b,$c,$d,$e,$f,$g,$h,$i,$j,$k,$l) = splice #_,0,12, ( ('NULL') x $padding_required );
my #dozens;
local $LIST_SEPARATOR = ', '; # how to join elements within each dozen
while(#_){
push #dozens, "SELECT #{[ splice #_,0,12 ]} FROM DUAL"
};
$LIST_SEPARATOR = "\n union all\n "; # how to join #dozens
return <<"EXP";
WITH t AS (
select $a A, $b B, $c C, $d D, $e E, $f F, $g G, $h H, $i I, $j J, $k K, $l L FROM DUAL
union all
#dozens
)
select A from t union select B from t union select C from t union
select D from t union select E from t union select F from t union
select G from t union select H from t union select I from t union
select J from t union select K from t union select L from t
EXP
}
One would use that like so:
my $bases_list_expr = big_IN_list(list_your_bases());
$dbh->do(<<"UPDATE");
update bases_table set belong_to = 'us'
where id in ($bases_list_expr)
UPDATE
Instead of using IN clause, can you try using JOIN with the other table, which is fetching the id. that way we don't need to worry about limit. just a thought from my side.
Instead of SELECT * FROM table1 WHERE ID IN (1,2,3,4,...,1000);
Use this :
SELECT * FROM table1 WHERE ID IN (SELECT rownum AS ID FROM dual connect BY level <= 1000);
*Note that you need to be sure the ID does not refer any other foreign IDS if this is a dependency. To ensure only existing ids are available then :
SELECT * FROM table1 WHERE ID IN (SELECT distinct(ID) FROM tablewhereidsareavailable);
Cheers