Performance using union

I am using union of around 6 queries in a report. The same query in the database runs faster where as the report takes long time. Please suggest what can be done.
thanks,
deep

Since union does an extra sort it has a performance difference compared to union all.
SQL> select user from dual union select user from dual ;
USER
HR
SQL> select user from dual union all select user from dual ;
USER
HR
HRİf there is up to date and appropriate object statistics Oracle's Cost Based Optimizer will choose best access path, join method and join order depending on your query. Only exceptions are hints, outlines and sql profiles since they stabilize the execution plan.
For further commenting please post your oracle version, query's test results and its statistics taken from sql*plus timing and autotrace options - http://www.bhatipoglu.com/entry/17/oracle-performance-analysis-tracing-and-performance-evaluation

Similar Messages

  • Performance using UNION ALL

    Hello
    i have 2 schemas S1 and S2 containing complex relational tables. The tables in each schema are related to each other via foreign key relationships. i made views for feature tables in both the schemas , querying column values from their related tables.
    the data structure in both the schemas are exactly the same. Dut to management reasons we have to split them in 2 schemas. S1 contain data for region A and S2 contains data from region B. Now the client wants to see a combined data from region A & B.
    we are planning to create another schema S3 and make views combining views from S1 and S2 in both schemas (V1 in S1 + V1 in S2) using UNION ALL.
    Does UNION ALL will make use of the indexes we already built for parent tables in S1 and S2? Will there be a performance degradation using this approach? What can be the best approach? Our client needs to see real time data....
    regards
    sam

    Since union does an extra sort it has a performance difference compared to union all.
    SQL> select user from dual union select user from dual ;
    USER
    HR
    SQL> select user from dual union all select user from dual ;
    USER
    HR
    HRİf there is up to date and appropriate object statistics Oracle's Cost Based Optimizer will choose best access path, join method and join order depending on your query. Only exceptions are hints, outlines and sql profiles since they stabilize the execution plan.
    For further commenting please post your oracle version, query's test results and its statistics taken from sql*plus timing and autotrace options - http://www.bhatipoglu.com/entry/17/oracle-performance-analysis-tracing-and-performance-evaluation

  • How do I write a Dll to perform a union in visual studio for use in LabVIEW?

    Hello,
    I'm new to writing dll(s). I'm attempting to write a Dll that will perform a union on a number from LabVIEW and then return the result to LabVIEW for my use. I've been struggling with this for a few days and I'm finally giving in to get some help.
    This screenshot is the only description that I have to help me with what I am trying to do. Basically, I'm trying to pass a value that will be different based on a measured partial discharge value. In the screen below, the value used is "1061111989" This number is my reading. I need to pass this value from labVIEW into my dll to perform a union on it.
    In my Dll, I need to write MeterReading.IntVal's value and get the MeterReading.FloatVal back.
    I have Visual Studio 2012 Full and LabVIEW 2012 Full, I'm LabVIEW CLAD and I've written 17 test floors in the US to date; however, I've never had any need of Visual Studio until now. Can anyone help me out with this?
    Thanks in advance, -Chris
    -Chris
    "You must be some sort of an engineer?" -Close Friend
    Solved!
    Go to Solution.

    Sometimes, I try to solve simple issues in very complicated ways. What got me so confused here was the solution from the engineer of the device that I am reading from was using a union to get the value. I'm not familiar with unions so I thought that it was some structure that was not creatable in LabVIEW. Anyways, a typecast to single point gave me the proper value. Thank you.
    -Chris
    "You must be some sort of an engineer?" -Close Friend

  • How to get the values in a single row without using union

    Hi,
    I have a table with the following structure and data
    empid     address     phoneno     emailid
    1001     xyz          
    1001          1234234     
    1001               [email protected]
    1002          23434     
    1002               [email protected]
    1003     abcd          
    1003               [email protected]
    1004               [email protected]
    I need to have a result in this format.
    emp id     address     phoneno     emailid
    1001     xyz     1234234     [email protected]
    1002          23434     [email protected]
    1003     abcd          [email protected]
    1004               [email protected]
    I can do it using union however that gives a performance issues with a large table. So I wish to do using in any other way using lead or something, but with the complexity about the data, I couldn't do it.
    Can anyone please help me?
    Natarajan
    Edited by: Nattu on Dec 3, 2009 3:50 PM

    Select employee_id, max(address), max(phone), max(email)
    from emp
    group by employee_id;Max

  • Need sql query to remove duplicates using UNION ALL clause

    Hi,
    I have a sql query which has UNION clause.But the UNION clause is causing some performance issues.
    To overcome that I have used UNION ALL to improve performance but its returning duplicates.
    Kindly anyone send a sample SQL query where my primary objective is used to use UNION ALL clause and to consider unique rows (elimating duplicate
    ones)
    Any help will be needful for me
    Thanks and Regards

    why not UNION? :(
    another way also use MINUS
    SQL>
    SQL> with t as
      2  (
      3  select 1 if from dual union all
      4  select 2 if from dual union all
      5  select 1 if from dual union all
      6  select 3 if from dual union all
      7  select 3 if from dual
      8  )
      9  ,t2 as
    10  (
    11  select 1 if from dual union all
    12  select 2 if from dual union all
    13  select 3 if from dual union all
    14  select 4 if from dual union all
    15  select 5 if from dual
    16  )
    17  (select if from t
    18  union all
    19  select if from t2)
    20  /
            IF
             1
             2
             1
             3
             3
             1
             2
             3
             4
             5
    10 rows selected
    SQL> so
    SQL>
    SQL> with t as
      2  (
      3  select 1 if from dual union all
      4  select 2 if from dual union all
      5  select 1 if from dual union all
      6  select 3 if from dual union all
      7  select 3 if from dual
      8  )
      9  ,t2 as
    10  (
    11  select 1 if from dual union all
    12  select 2 if from dual union all
    13  select 3 if from dual union all
    14  select 4 if from dual union all
    15  select 5 if from dual
    16  )
    17  (select if from t
    18  union all
    19  select if from t2)
    20  minus
    21  select -99 from dual
    22  /
            IF
             1
             2
             3
             4
             5
    SQL>

  • Using union

    I have these views using union
    create or replace view V_CONSULTATION_SUMMARY
    AS SELECT
    Consul_date "DATE",
    Consultation_No,
    TO_NUMBER(NULL) "RECEIPT_NO",
    Consultation_fee "CREDIT",
    TO_NUMBER(NULL) "AMOUNT_PAID"
    FROM consultation
    union select
    B.Receipt_Date "DATE",
    A.Consultation_No,
    B.Receipt_No "RECEIPT_NO",
    TO_NUMBER(NULL) "CREDIT",
    B.Amount_Paid "AMOUNT_PAID"
    FROM consultation A, Receipt B WHERE
    b.Consultation_No=A.Consultation_No
    ORDER BY "DATE", Consultation_No, RECEIPT_NO;
    create or replace view V_PATIENT_FINANCIAL_RECORDS
    AS SELECT
    A.PID,
    B.*
    FROM cONSULTATION A, V_CONSULTATION_SUMMARY B
    WHERE A.Consultation_No=B.Consultation_No;
    then I tried to access it from oracle forms using datablock wizard to access both views, and both of them failed. could some one tell me why. The error message is:
    FRM-40505: ORACLE error: unable to perform query
    thank's

    Why not?
    but, you should try it next time ->
    insert into <dest_table>
    select BKNO,BKNAME,AUTHORNAME,PUBLISHER,PRICE,STATUS
    from (
              select BKNO,BKNAME,AUTHORNAME,PUBLISHER,PRICE,STATUS
              from lib_bk_det
              union
              select BKNO,BKNAME,AUTHORNAME,PUBLISHER,PRICE,STATUS
              from lib_bk_det_20
          );N.b.: Not Tested...
    Regards.
    Satyaki de.

  • How to use 'UNION' between two different databaseservers

    Hello,
    Could someone help me out. I am trying to find out if and how to use 'UNION' between two different databaseservers.
    We have 2 different queries, each queries on a different database; one MySQL the other MSSQL.
    Could someone tell me how to use 'UNION' between thes 2 queries?
    Thanks in advance,
    Samir Benalla

    Hello
    You may use openrowset statement, (OPENROWSET (Transact-SQL))., but before you use this, you must configure your server
    sample:
    SELECT a.*
    FROM OPENROWSET('SQLNCLI', 'Server=Seattle1;Trusted_Connection=yes;',
         'SELECT GroupName, Name, DepartmentID
          FROM AdventureWorks2012.HumanResources.Department
          ORDER BY GroupName, Name') AS a
    UNION
         SELECT GroupName, Name, DepartmentID
          FROM AdventureWorks2012.HumanResources.Department
          ORDER BY GroupName, Name
    With this you can define a connection using native client to server Seattle1, and execute a query there, The results will be spooled on your server.
    Connectionstring
    Server=[SERVER_NAME];datasource=[YOUR DATABASE NAME];user_id=sa;password=sapassword'
    if you use FQDN on your Query, than the datasource parameter in connection string can be letf out.
    Regards
    János.
    take care of performance, it can be very slow,

  • Adding new column in an existing report which was build using Union

    While working in OBIEE 11g I encounter an issue.
    My existing report was build using UNION at Criteria Tab in Analysis. Now I have a requirement to add a new column into the same report. For each criteria I have added the new column but when I go back to the "Result Columns". I see a new field added but it is not allowing me to open or edit column properties for that new column & at the same time it is not allowing me to navigate to other tabs like Results, Promts, and Advanced.
    I don’t want to build this report from scratch. Is there any workaround to get it resolved?

    Hi,
    Just check it once the new added column data types are mismatched or not?
    and the new added column should be navigated into excluded section, so u should edit the report and dragged into the table column section.
    Thanks..

  • Query takes long when using UNION

    Hi ,
    I habe a query as follows;
    SELECT
                        '9999' site_id,
                        m.ghi_prov_num provnum,
                           SUBSTR (l.seq_num, 1, 3)provloc,
                        t.dea_number dea,
                            t.license_number statelicensenumber ,
                            n.npi_num npi,
                            m.prefix prefixname,
                            m.lastname lastname,
                            m.firstname firstname,
                            t.middle_name middleinitial,
                            m.suffix suffixname,
                            null clinicname,
                            l.street1 addressline1,
                            l.street2 addressline2,
                            l.city city,
                            l.state state,
                            l.zip5 zip,
                            l.phone phoneprimary,
                            null ext,
                            null fax,
                            null email,
                            null alt_phone,
                            null alt_phone_ext
                     FROM provider m, LOCATION l, npi n,TEMP_VITAL_CACTUS t,test_provider_pin pin
                      WHERE m.ghi_prov_num=l.ghi_prov_num
                          and m.ghi_prov_num=n.ghi_prov_num(+)
                          and m.ghi_prov_num=t.ghi_prov_num(+)
                          and m.tax_id=pin.tax_id
         UNION
          SELECT   
                        '9999', m.ghi_prov_num ,
                            m.location provloc,
                           null  ,
                           null  ,
                            n.npi_num  ,
                            null ,
                            m.lastname ,
                            m.firstname  ,
                            null,
                            null  ,
                            null  ,
                            m.street1  ,
                            m.street2  ,
                            m.city ,
                            m.state  ,
                            m.zip5 ,
                            m.phone  ,
                            null  ,
                            null  ,
                            null  ,
                            null  ,
                            null
                           FROM dental_provider m, npi n,test_provider_pin pin
                       WHERE m.ghi_prov_num=n.tax_id(+)
                           and m.location=n.location(+)
                            and pin.tax_id=m.ghi_prov_num;The query takes for ever;
    But Individual query takes less than a sec to execute.Is there any way can i rewrite the query?
    Please help
    Hena.

    user11253970 wrote:
    But Individual query takes less than a sec to execute.Is there any way can i rewrite the query?Have a feeling you are using Toad/SQL Navigator or similar tool which returns data one screen at a time. If so, then it does not "takes less than a sec to execute" but rather to fetch first screen of rows. When you use UNION Oracle has to return distinct rows from both queries. Therefore it must fetch not just first screen but all rows. To verify, issue first query and in yiour GUI tool click on get last screen. Then you'll know how long whole select takes. Do the same for second query. Also, do you need distinct rows or akll rows? IF all rows, change UNION to UNION ALL.
    SY.

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    Not sure if this is the best practice.
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    Regards,
    Sam

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  • How to use union statement with declare & set function?

    Hi Experts,
            i  have small query about how to use union statement with declare & set function?
    Example as below :
    DECLARE @name AS date
    Declare @name2  AS date
    /* SELECT FROM [2013].[dbo].[OINV] T0 */
    /* WHERE */
    SET @name = /* T0.DocDate */ '[%1]'
    SET @name2 = /* T0.DocDate */ '[%2]'
    select  '2013',t5.U_salmannm,t1.CardName,t2.sumapplied as CollectionAmount,t2.DcntSum ,t3.DocTotal as InvoiceTotal,
    datediff(dd,t3.DocDate,t1.Docdate) as Days
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    inner join 2013.dbo.RCT2 t2 on t1.DocNum = t2.DocNum
    left join 2013.dbo.oinv t3 on
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    inner join 2013.dbo.ocrd t4 on t1.Cardcode = t4.CardCode
    inner join [2013].[dbo].[@CQ_RTSM] t5 on t4.U_BeatCode = t5.U_RoutCode
    where t2.DcntSum <> 0.000000 and t3.DocDate between [%1] and [%2]
    Union
    /* SELECT FROM [2014].[dbo].[OINV] T0 */
    /* WHERE */
    SET @name = /* T0.DocDate */ '[%1]'
    SET @name2 = /* T0.DocDate */ '[%2]'
    select  '2014',t5.U_salmannm,t1.CardName,t2.sumapplied as CollectionAmount,t2.DcntSum ,t3.DocTotal as InvoiceTotal,
    datediff(dd,t3.DocDate,t1.Docdate) as Days
    from 2014.dbo.orct t1
    inner join 2014.dbo.RCT2 t2 on t1.DocNum = t2.DocNum
    left join 2014.dbo.oinv t3 on
    t3.docentry = t2.baseAbs
    inner join 2014.dbo.ocrd t4 on t1.Cardcode = t4.CardCode
    inner join [2014].[dbo].[@CQ_RTSM] t5 on t4.U_BeatCode = t5.U_RoutCode
    where t2.DcntSum <> 0.000000 and t3.DocDate between [%1] and [%2]

    You have to create stored procedure in SQL only .
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    Exec @Test '20140101' '20140501'
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    Example
    Create Proc [@Test]
    as begin
    DECLARE @name AS date
    Declare @name2  AS date
    /* SELECT FROM [2013].[dbo].[OINV] T0 */
    /* WHERE */
    select  '2013',t5.U_salmannm,t1.CardName,t2.sumapplied as CollectionAmount,t2.DcntSum ,t3.DocTotal as InvoiceTotal,
    datediff(dd,t3.DocDate,t1.Docdate) as Days
    from 2013.dbo.orct t1
    inner join 2013.dbo.RCT2 t2 on t1.DocNum = t2.DocNum
    left join 2013.dbo.oinv t3 on
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    inner join [2013].[dbo].[@CQ_RTSM] t5 on t4.U_BeatCode = t5.U_RoutCode
    where t2.DcntSum <> 0.000000 and t3.DocDate between @Name and @Name2
    Union
    /* SELECT FROM [2014].[dbo].[OINV] T0 */
    /* WHERE */
    select  '2014',t5.U_salmannm,t1.CardName,t2.sumapplied as CollectionAmount,t2.DcntSum ,t3.DocTotal as InvoiceTotal,
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    inner join 2014.dbo.RCT2 t2 on t1.DocNum = t2.DocNum
    left join 2014.dbo.oinv t3 on
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    inner join [2014].[dbo].[@CQ_RTSM] t5 on t4.U_BeatCode = t5.U_RoutCode
    where t2.DcntSum <> 0.000000 and t3.DocDate between
    between @Name and @Name2
    end

  • Join two tables using union

    Hi Gurus,
    I have three tables. I want to join all tables using union in SQL statement. The query is returning all the records from both tables but i only require unique rows based on a specific column value. Here is my table structure -
    TableA -
    LIC_ID          NUMBER(10)     NOT NULL
    LIC_NUMBER     VARCHAR2(20)
    COMMENCE_DATE     DATE
    EXPIRY_DATE     DATE
    TERM          VARCHAR2(20)LIC_ID is the primary key in this table -
    Sample data from TableA
    LIC_ID          LIC_NUMBER     COMMENCE_DATE          EXPIRY_DATE     TERM
    2          TR4323          12/04/2008          11/03/2010     2 Years
    34          TR5432          23/07/2009          22/07/2010     1 Year
    45          TR5321          24/06/2009          23/06/2010     1 Year
    65          TR6666          23/07/2010          22/07/2011     1 Year
    32          TR2423          30/05/2010          29/05/2011     1 YearTableB -
    MAR_ID          NUMBER(10)     NOT NULL
    LIC_ID          NUMBER(10)     NOT NULL
    ZONE_NAME     VARCHAR2(20)
    DEPARTMENT     VARCHAR2(20)
    ACTIVITIES     VARCHAR2(200)
    COMMENTS     VARCHAR2(200)MAR_ID is the primary key in this table and LIC_ID is the foreign key on TableA
    Sample data from TableB -
    MAR_ID          LIC_ID          ZONE_NAME     DEPARTMENT     ACTIVITIES     COMMENTS
    23          2          ZONE A          IT          NONE               
    43          34          ZONE B          IT          NONE
    33          65          ZONE C          ACCOUNT          NONE     
              TableC
    REC_ID          NUMBER(10)     NOT NULL
    LIC_ID          NUMBER(10)     NOT NULL
    DIST_NAME     VARCHAR2(20)
    REGION          VARCHAR2(20)
    ACTIVITIES     VARCHAR2(200)
    COMMENTS     VARCHAR2(200)REC_ID is the primary key in this table and LIC_ID is the foreign key.
    Sample data -
    REC_ID          LIC_ID          DIST_NAME     REGION          ACTIVITIES     COMMENTS
    2          45          SA          NORTH          NONE
    3          65          TA          NORTH          NONE
    5          32          NT          SOUTH          NONEHere is my sql query -
    select a.lic_id, a.lic_number, a.commence_date, a.expiry_date from
    TableA a, TableB b
    where a.lic_id=b.lic_id
    union
    select a.lic_id, a.lic_number, a.commence_date, a.expiry_date from
    TableA a, TableC c
    where a.lic_id=c.lic_idThe above query returns -
    lic_id          lic_number     commence_date          expiry_date          
    2          TR4323          12/04/2008          11/03/2010     
    34          TR5432          23/07/2009          22/07/2010     
    45          TR5321          24/06/2009          23/06/2010     
    65          TR6666          23/07/2010          22/07/2011     
    32          TR2423          30/05/2010          29/05/2011
    65          TR6666          23/07/2010          22/07/2011     LIC_ID 65 exists in both table TableB and TableC hence it repeats in query but I want to display that only once. How can I do that? I want to return unique record on LIC_NUMBER.
    Hope this make sence.
    Many thanks,
    Tajuddin

    Thanks for all your reply and suggestions. David altering session did not work.
    Sven your idea helped me to figure it out what to do. I found a way around to fix it. Here is my current code -
    select a.lic_id, a.lic_number, a.commence_date, a.expiry_date from
    TableA a, TableB b
    where a.lic_id=b.lic_id
    union
    select a.lic_id, a.lic_number, a.commence_date, a.expiry_date from
    TableA a, TableC c
    where a.lic_id=c.lic_id and c.lic_id not in ( select lic_id from TableB)This will exclude any LIC_ID exists in TableB.
    Thanks again for your help guys.
    Regards,
    M Tajuddin
    Web: http://tajuddin.whitepagesbd.com
    Blog: http://aspblog.whitepagesbd.com

  • Writing query using UNION Operator

    Question -
    (1)
    Write an SQL Statement to list the following items: Customer ID, Customer Name, number of invoices, sum of total for invoices. Ensure that all customers are returned in the result set.
    Answer for the above is written as below by one person. That seams to be correct. Is there another way of writing this same query.;
    select c.CUSTOMER_ID,c.NAME,i.cnt,i.s
    from gee_customer c,(select customer_id,count(*) as cnt, sum(TOTAL) as s
    from gee_invoice
    group by customer_id) i
    where c.CUSTOMER_ID = i.customer_id (+)
    (2)
    My other question is How to write the above answer (or what you sugest) using UNION operator ?
    Any ideas please
    Message was edited by:
    user483578

    In fact the outer join means you use the union of two result sets - usual join result
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    SQL> select d.deptno, e.ename from emp e, dept d
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      3  order by 1,2
      4  /
        DEPTNO ENAME
            10 CLARK
            10 KING
            10 MILLER
            20 ADAMS
            20 FORD
            20 JONES
            20 SCOTT
            20 SMITH
            30 ALLEN
            30 BLAKE
            30 JAMES
            30 MARTIN
            30 TURNER
            30 WARD
            40
    15 rows selected.
    SQL> select d.deptno,e.ename from emp e, dept d
      2  where d.deptno = e.deptno
      3  union
      4  select deptno, null
      5  from dept d where not exists (select null from emp e where e.deptno = d.deptno)
      6  order by 1,2
      7  /
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            10 CLARK
            10 KING
            10 MILLER
            20 ADAMS
            20 FORD
            20 JONES
            20 SCOTT
            20 SMITH
            30 ALLEN
            30 BLAKE
            30 JAMES
            30 MARTIN
            30 TURNER
            30 WARD
            40
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    with i as (select customer_id,count(*) as cnt, sum(TOTAL) as s
    from gee_invoice group by customer_id)
    select c.CUSTOMER_ID,c.NAME,i.cnt,i.s
    from gee_customer c, i
    where c.CUSTOMER_ID = i.customer_id
    union
    select c.CUSTOMER_ID,c.NAME,null,null
    from gee_customer c
    where not exists (select null from i where c.CUSTOMER_ID = i.customer_id)
    Rgds.

  • Using Union in popup LOV

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