I have a procedure that returns multiple rows on some criteria and in specific order. These rows are separated into few pages (50 rows per page).
How can I retrieve all rows from page having some specific row.
I've created a query the query that do this work, but it is not optimized and have huge impact on performance. Help me please to optimize it or give an alternative to it:
select *
from
(
select file_id, row_number() over (order by rownum) rn
from my_table
)
where trunc(rn/50) = (
select trunc(rn/50) from
(select t.*, rownum rn from my_table t)
where file_id = 29987);
You have to adjust it a little...
with tab as
(
-- the
-- row_number() over (order by rownum) rn
-- should be here
select level + 1000 as val
, level/50 as rn_50
from dual
connect by
level < 140
)
, val as
(
select rn_50
from tab
where val = 1004 -- pg 1
--where val = 1051 -- pg 2
--where val = 1101 -- pg 3
)
select *
from tab t
where rn_50 >= (select floor(rn_50) from val)
and rn_50 <= (select ceil (rn_50) from val)
;
Related
The table contains numbers from 944900000 to 944999999 and i want to split these numbers into ranges of 1000 each like
944900000 to 944900999 -- 1000
944901000 to 944901999 -- 1000
..
..
944999000 to 944999999 -- 1000
is there any way to generate this through oracle SQL not with PL/SQL
You could also use this.
--Your data
CREATE TABLE your_table(your_column) AS
SELECT 944900000 + LEVEL - 1
FROM dual
CONNECT BY 944900000 + LEVEL < 944999999 + 2
;
--from 944900000 to 944999999
WITH cte AS (
SELECT your_column, CASE WHEN MOD(your_column, 1000) = 0 THEN your_column END start_range
FROM your_table
)
SELECT start_range, end_range
FROM (
SELECT start_range, CASE WHEN start_range IS NOT NULL THEN LEAD(your_column, 999)OVER(ORDER BY your_column) END end_range
FROM cte
)T
WHERE end_range IS NOT NULL /*because of the last execution of lead function in the inline view t*/
GROUP BY start_range, end_range
ORDER BY 1, 2
;
You could use ROW_NUMBER to number all records according to increasing number value. Then, compute a DENSE_RANK using the "group" of increments of 1000 to which each record belongs.
WITH cte AS (
SELECT t.*, ROW_NUMBER OVER (ORDER BY col) rn
FROM yourTable t
),
cte2 AS (
SELECT t.*, DENSE_RANK() OVER (ORDER BY FLOOR(rn / 1000)) dr
FROM cte t
)
SELECT *
FROM cte2
WHERE dr = 2; -- e.g. for 2nd partition of 1000 records
I have the following setup, which works fine and generates output as expected.
I'm trying to add the locations subquery into the CTE so my output will have a random location_id for each row.
The subquery is straight forward and should work but I am getting syntax errors when I try to place it into the 'data's CTE. I was hoping someone could help me out.
CREATE TABLE employees(
employee_id NUMBER(6),
emp_name VARCHAR2(30)
);
INSERT INTO employees(
employee_id,
emp_name
) VALUES
(1, 'John Doe');
INSERT INTO employees(
employee_id,
emp_name
) VALUES
(2, 'Jane Smith');
INSERT INTO employees(
employee_id,
emp_name
) VALUES
(3, 'Mike Jones');
CREATE TABLE locations AS
SELECT level AS location_id,
'Door ' || level AS location_name
FROM dual
CONNECT BY level <=
with rws as (
select level rn from dual connect by level <= 5 ),
data as ( select e.*,round (dbms_random.value(1,5)
) n from employees e)
select employee_id,
emp_name,
trunc (sysdate) + dbms_random.value (0, 5) AS random_date
from rws
join data d on rn <= n
order by employee_id;
-- trying to make this work
with rws as ( select level rn from dual connect by level <= 5 ),
data as ( select e.*, loc.location_id = (
select location_id
from locations order by dbms_random.value()
fetch first 1 row only
),
round (dbms_random.value(1,5)
) n from employees e )
select employee_id,
emp_name,
trunc (sysdate) + dbms_random.value (0, 5) AS random_date
from rws
join data d on rn <= n
order by employee_id;
You need to alias the subquery column expression, rather than trying to assign it to a [variable] name. So instead of this:
with rws as ( select level rn from dual connect by level <= 5 ),
data as ( select e.*, loc.location_id = (
select location_id
from locations order by dbms_random.value()
fetch first 1 row only
),
round (dbms_random.value(1,5)
) n from employees e )
you would do this:
with rws as (
select level rn
from dual
connect by level <= 5
),
data as (
select e.*,
(
select location_id
from locations
order by dbms_random.value()
fetch first 1 row only
) as location_id,
round (dbms_random.value(1,5)) as n
from employees e
)
db<>fiddle
But yes, you'll get the same location_id for each row, which probably isn't what you want.
There are probably better ways to avoid it (or to approach whatever you're actually trying to achieve) but one option is to force the subquery to be correlated by adding something like:
where location_id != -1 * e.employee_id
db<>fiddle
although that might be expensive. It's probably worth asking a new question about that specific aspect.
I am getting the same location_id for every employee_id, which I don't want either.
The subquery is in the wrong place then; move it to the main query, and correlate against both ID and n:
with rws as (
select level rn
from dual
connect by level <= 5
),
data as (
select e.*,
round (dbms_random.value(1,5)) as n
from employees e
)
select d.employee_id,
d.emp_name,
(
select location_id
from locations
where location_id != -1 * d.employee_id * d.n
order by dbms_random.value()
fetch first 1 row only
) as location_id,
trunc (sysdate) + dbms_random.value (0, 5) AS random_date
from rws r
join data d on r.rn <= d.n
order by d.employee_id;
db<>fiddle
Or move the location part to a new CTE, I suppose, with its own row number; and join that on one of your other generated values.
when i run the query:
select *
from ( select a.*,
ROWNUM rnum
from ( select *
from test
order by null ) a
where ROWNUM <= 2000 )
where rnum >=1
I'm getting all the columns along with rownum as a separate column which I don't want, How to achieve this or is there any way to limit records?
Since the final filter is for ROWNUM >= 1 (which will always be true), you can eliminate that and just use:
select *
from (
select *
from test
order by null
)
where ROWNUM <= 2000
(Note: ORDER BY NULL will apply a non-deterministic ordering.)
If you want to specify a different starting row then you will need to specify the columns you want to return:
select col_1,
col_2,
-- ...
col_n
from (
select a.*,
ROWNUM rnum
from (
select *
from test
order by null
) a
where ROWNUM <= 2000
)
WHERE rnum > 1000
In Oracle 12c you can use:
SELECT *
FROM test
ORDER BY NULL
FETCH FIRST 2000 ROWS ONLY;
or
SELECT *
FROM test
ORDER BY NULL
OFFSET 1000 ROWS FETCH NEXT 1000 ROWS ONLY;
i'm trying to get total count by using UNION operator but it gives wrong count.
select count(*) as companyRatings from (
select count(*) hrs from (
select distinct hrs from companyA
)
union
select count(*) financehrs from (
select distinct finance_hrs from companyB
)
union
select count(*) hrids from (
select regexp_substr(hr_id,'[^/]+',1,3) hrid from companyZ
)
union
select count(*) cities from (
select regexp_substr(city,'[^/]+',1,3) city from companyY
)
);
individual query's working fine but total count not matching.
individual results here: 12 19 3 6
present total count: 31
Actual total count:40.
so there is any alternate solution without UNION operator?
To add values you'd use +. UNION is to add data sets.
select
(select count(distinct hrs) from companyA)
+
(select count(distinct finance_hrs) from companyB)
+
(select count(regexp_substr(hr_id,'[^/]+',1,3)) from companyZ)
+
(select count(regexp_substr(city,'[^/]+',1,3)) from companyY)
as total
from dual;
But I agree with juergen d; you should not have separate tables per company in the first place.
Edit. Updated query using Sum
select sum(cnt) as companyRatings from
(
select count(*) as cnt from (select distinct hrs from companyA)
union all
select count(*) as cnt from (select distinct finance_hrs from companyB)
union all
select count(*) as cnt from (select regexp_substr(hr_id,'[^/]+',1,3) hrid from companyZ)
union all
select count(*) as cnt from (select regexp_substr(city,'[^/]+',1,3) city from companyY)
)
Previous answer:
Try this
SELECT (
SELECT count(*) hrs
FROM (
SELECT DISTINCT hrs
FROM companyA
)
)
+
(
SELECT count(*) financehrs
FROM (
SELECT DISTINCT finance_hrs
FROM companyB
)
)
+
(
SELECT count(*) hrids
FROM (
SELECT regexp_substr(hr_id, '[^/]+', 1, 3) hrid
FROM companyZ
)
)
+
(
SELECT count(*) cities
FROM (
SELECT regexp_substr(city, '[^/]+', 1, 3) city
FROM companyY
)
)
AS total_count
FROM dual
I have identified a way to get fast paged results from the database using CTEs and the Row_Number function, as follows...
DECLARE #PageSize INT = 1
DECLARE #PageNumber INT = 2
DECLARE #Customer TABLE (
ID INT IDENTITY(1, 1),
Name VARCHAR(10),
age INT,
employed BIT)
INSERT INTO #Customer
(name,age,employed)
SELECT 'bob',21,1
UNION ALL
SELECT 'fred',33,1
UNION ALL
SELECT 'joe',29,1
UNION ALL
SELECT 'sam',16,1
UNION ALL
SELECT 'arthur',17,0;
WITH cteCustomers
AS ( SELECT
id,
Row_Number( ) OVER(ORDER BY Age DESC) AS Row
FROM #Customer
WHERE employed = 1
/*Imagine I've joined to loads more tables with a really complex where clause*/
)
SELECT
name,
age,
Total = ( SELECT
Count( id )
FROM cteCustomers )
FROM cteCustomers
INNER JOIN #Customer cust
/*This is where I choose the columns I want to read, it returns really fast!*/
ON cust.id = cteCustomers.id
WHERE row BETWEEN ( #PageSize * #PageNumber - 1 ) AND ( #PageSize * ( #PageNumber ) )
ORDER BY row ASC
Using this technique the returned results is really really fast even on complex joins and filters.
To perform paging I need to know the Total Rows returned by the full CTE. I have "Bodged" this by putting a column that holds it
Total = ( SELECT
Count( id )
FROM cteCustomers )
Is there a better way to return the total in a different result set without bodging it into a column? Because it's a CTE I can't seem to get it into a second result set.
Without using a temp table first, I'd use a CROSS JOIN to reduce the risk of row by row evaluation on the COUNT
To get total row, this needs to happen separately to the WHERE
WITH cteCustomers
AS ( SELECT
id,
Row_Number( ) OVER(ORDER BY Age DESC) AS Row
FROM #Customer
WHERE employed = 1
/*Imagine I've joined to loads more tables with a really complex where clause*/
)
SELECT
name,
age,
Total
FROM cteCustomers
INNER JOIN #Customer cust
/*This is where I choose the columns I want to read, it returns really fast!*/
ON cust.id = cteCustomers.id
CROSS JOIN
(SELECT Count( *) AS Total FROM cteCustomers ) foo
WHERE row BETWEEN ( #PageSize * #PageNumber - 1 ) AND ( #PageSize * ( #PageNumber ) )
ORDER BY row ASC
However, this isn't guaranteed to give accurate results as demonstrated here:
can I get count() and rows from one sql query in sql server?
Edit: after a few comments.
How to avoid a CROSS JOIN
WITH cteCustomers
AS ( SELECT
id,
Row_Number( ) OVER(ORDER BY Age DESC) AS Row,
COUNT(*) OVER () AS Total --the magic for this edit
FROM #Customer
WHERE employed = 1
/*Imagine I've joined to loads more tables with a really complex where clause*/
)
SELECT
name,
age,
Total
FROM cteCustomers
INNER JOIN #Customer cust
/*This is where I choose the columns I want to read, it returns really fast!*/
ON cust.id = cteCustomers.id
WHERE row BETWEEN ( #PageSize * #PageNumber - 1 ) AND ( #PageSize * ( #PageNumber ) )
ORDER BY row ASC
Note: YMMV for performance depending on 2005 or 2008, Service pack etc
Edit 2:
SQL Server Central shows another technique where you have reverse ROW_NUMBER. Looks useful
#Digiguru
OMG, this really is the wholy grail!
WITH cteCustomers
AS ( SELECT id,
Row_Number() OVER(ORDER BY Age DESC) AS Row,
Row_Number() OVER(ORDER BY id ASC)
+ Row_Number() OVER(ORDER BY id DESC) - 1 AS Total /*<- voodoo here*/
FROM #Customer
WHERE employed = 1
/*Imagine I've joined to loads more tables with a really complex where clause*/
)
SELECT name, age, Total
/*This is where I choose the columns I want to read, it returns really fast!*/
FROM cteCustomers
INNER JOIN #Customer cust
ON cust.id = cteCustomers.id
WHERE row BETWEEN ( #PageSize * #PageNumber - 1 ) AND ( #PageSize * ( #PageNumber ) )
ORDER BY row ASC
So obvious now.