I'm using Db2 on AS/400, and I am trying to execute a JPQL query that will return results from row x to row y.
In SQL this works:
select cur.* from (
SELECT ROW_NUMBER() OVER() AS ROWNUM FROM tableName d) as cur
WHERE cur.ROWNUM > 0 AND cur.ROWNUM < 10
How can I do this in JQPL? I tried it in many ways but every time I got an exception.
I want to limit my result inside the query, and not by using the setMaxResult, setFirstResult methods.
Query q = em.createQuery("select e from SomeEntity e")
.setFirstResult(0)
.setMaxResults(10);
That cannot be done. JPQL operates to entities and entities are mapped to tables in database. Row number in db2 is concept in result set, not in database table.
Related
normal sql query which work correctly in db in sql developer passing values for bID and period.
SELECT * FROM A WHERE abcID IN (SELECT abcID FROM B WHERE bID=1) AND period=3
in project at Repository class I passed as this
#Query("select a from A where a.abcID IN:(select b.abcId from B where bID=:RevID) and period=:period")
error comes as
Space is not allowed after parameter prefix ':' [select a from A
where a.abcID IN:(select b.abcId from B where bID=:RevID) and
period=:period]
I want to know how should I insert above query correctly in #Query annotation
First of all I would tell you below points.
you can't use select query as select a from A where a.abcID. Here a is a column so can't define something like a.abcID. It need to be select column from tableA a where a.abcID
Same for query use in IN clause. It needs to be like select b.abcId from tableB b where b.bID=:RevID
What you use as :RevID, :period need to be passed as #Param("RevID"), #Param("period") to the query method.
This is the query template.
#Query("select a.nameOfcolumnYouWantToRetrieve from tableA a where a.someColumn in(select b.someColumn from tableB b where b.columnValueOfTableBYouwantToMatch=:RevID) and a.period=:period")
Using this points, try below query.
#Query("select a.id from A a where a.abcID in(select b.abcId from B b where b.bID =:RevID) and a.period=:period")
I have created the following query:
select t.id, t.row_id, t.content, t.location, t.retweet_count, t.favorite_count, t.happened_at,
a.id, a.screen_name, a.name, a.description, a.followers_count, a.friends_count, a.statuses_count,
c.id, c.code, c.name,
t.parent_id
from tweets t
join accounts a on a.id = t.author_id
left outer join countries c on c.id = t.country_id
where t.row_id > %s
-- order by t.row_id
limit 100
Where %s is a number that starts at 0 and is incremented by 100 after each such query is conducted. I want to fetch all records from the database using this method, where I just increase the %s in the where condition. I found this approach on https://ivopereira.net/efficient-pagination-dont-use-offset-limit. I also included a column in my table which is corresponding to row number (I named it row_id). Now the problem is when I run this query the first time, it returns rows which have an row_id of 3 million. I would like the cursor (not sure if my terminology is correct) to start from rows with row_id 1 through 100 and so on. The table contains 7 million rows. Am I missing something obvious with which I could achieve my goal?
I have a nested select query that is returning the proper amount of rows. The query builds a recordset and compares it to a table and returns the records in the query that are not in the table.
I converted the select query to an update query. I am trying to populate the table with the rows returned from the query. When I run the update query it is returning with zero rows to update. I dont understand why because the select query is returning record and I am using the same code in the update query.
Thanks
Select Query: (This is returning several records)
Select *
From
(SELECT DISTINCT
ProductClass,SalProductClass.[Description],B.Branch,B.BranchDesc,B.Salesperson,B.Name,
CAST(0 AS FLOAT) AS Rate,'N' AS Split
FROM (SELECT SalBranch.Branch,SalBranch.[Description] AS BranchDesc,A.Salesperson,A.Name
FROM (SELECT DISTINCT
Salesperson,Name
FROM SalSalesperson
) A
CROSS JOIN SalBranch
) B
CROSS JOIN SalProductClass
) C
Left Outer Join RateComm On
RateComm.ProductClass = C.ProductClass and
RateComm.Branch = C.Branch And RateComm.Salesperson = C.Salesperson
Where RateComm.ProductClass is Null
Update Query: (This is returning zero records)
UPDATE RateComm
SET RateComm.ProductClass=C.ProductClass,RateComm.ProdClassDesc=C.ProdClassDesc,
RateComm.Branch=C.Branch,RateComm.BranchDesc=C.BranchDesc,RateComm.Salesperson=C.Salesperson,
RateComm.Name=C.Name,RateComm.Rate=C.Rate,RateComm.Split=C.Split
FROM (SELECT DISTINCT
ProductClass,SalProductClass.[Description] AS ProdClassDesc,B.Branch,B.BranchDesc,B.Salesperson,B.Name,
CAST(0 AS FLOAT) AS Rate,'N' AS Split
FROM (SELECT SalBranch.Branch,SalBranch.[Description] AS BranchDesc,A.Salesperson,A.Name
FROM (SELECT DISTINCT
Salesperson,Name
FROM SalSalesperson
) A
CROSS JOIN SalBranch
) B
CROSS JOIN SalProductClass
) C
LEFT OUTER JOIN RateComm ON C.ProductClass=RateComm.ProductClass AND
C.Salesperson=RateComm.Salesperson AND C.Branch=RateComm.Branch
WHERE RateComm.ProductClass IS NULL
It's difficult to update what doesn't exist. Have you tried an INSERT query instead?
I am new to Firebird and I am messing around in it's meta data to get some information about the table structure and etc.
My problem is that I can't seem to find some information about estimated table cardinality. Is there a way to get this information from Firebird?
Edit:
By cardinality i mean the number of rows in a table :) and for my use the select count(*) is not an option.
You can use an aproximative method, using the selectivity of primary key like this:
SELECT
R.RDB$RELATION_NAME TABLENAME,
(
CASE
WHEN I.RDB$STATISTICS = 0 THEN 0
ELSE 1 / I.RDB$STATISTICS
END) AS COUNTRECORDS8
FROM RDB$RELATIONS R
JOIN RDB$RELATION_CONSTRAINTS C ON (R.RDB$RELATION_NAME = C.RDB$RELATION_NAME AND C.RDB$CONSTRAINT_TYPE = 'PRIMARY KEY')
JOIN RDB$INDICES I ON (I.RDB$RELATION_NAME = C.RDB$RELATION_NAME AND I.RDB$INDEX_NAME = C.RDB$INDEX_NAME)
To get the number of rows in a table you use the COUNT() function as in any other SQL DB, ie
SELECT count(*) FROM table;
Why not use a query:
select count(distinct field_name)/(count(field_name) + 0.0000) from table_name
The closer result to 1 the higher cardinality of a specified column.
Currently I've a query as follows:
-- Query 1
SELECT
acc_code, acc_name, alias, LAmt, coalesce(LAmt,0) AS amt
FROM
(SELECT
acc_code, acc_name, alias,
(SELECT
(SUM(cr_amt)-SUM(dr_amt))
FROM
ledger_mcg l
WHERE
(l.acc_code LIKE a.acc_code + '.%' OR l.acc_code=a.acc_code)
AND
fy_id=1
AND
posted_date BETWEEN '2010-01-01' AND '2011-06-02') AS LAmt
FROM
acc_head_mcg AS a
WHERE
(acc_type='4')) AS T1
WHERE
coalesce(LAmt,0)<>0
Query 2 is same as Query 1 except that acc_type = '5' in Query 2. Query 2 always returns a resultset with a single row. Now, I need the union of the two queries i.e
Query 1
UNION
Query 2
only when the amt returned by Query 2 is less than 0. Else, I don't need a union but only the resulset from Query 1.
The best way I can think of is to create a parameterised scalar function. How best can I do this?
You could store the result of the first query into a temporary table, then, if the table wasn't empty, execute the other query.
IF OBJECT_ID('tempdb..#MultipleQueriesResults') IS NOT NULL
DROP TABLE #MultipleQueriesResults;
SELECT
acc_code, acc_name, alias, LAmt, coalesce(LAmt,0) AS amt
INTO #MultipleQueriesResults
FROM
(SELECT
acc_code, acc_name, alias,
(SELECT
(SUM(cr_amt)-SUM(dr_amt))
FROM
ledger_mcg l
WHERE
(l.acc_code LIKE a.acc_code + '.%' OR l.acc_code=a.acc_code)
AND
fy_id=1
AND
posted_date BETWEEN '2010-01-01' AND '2011-06-02') AS LAmt
FROM
acc_head_mcg AS a
WHERE
(acc_type='4')) AS T1
WHERE
coalesce(LAmt,0)<>0;
IF NOT EXISTS (SELECT * FROM #MultipleQueriesResults)
… /* run Query 2 */