SQL & PL/SQL :: What Is Hash Join And Sort Merge
Jun 12, 2012I tried to search on google for "Hash Join" And "Sort Merge". But unfortunatly i am unable to understand that articles. "Hash join" And "Sort Merge".
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Performance Tuning :: How Oracle Optimizer Choose Joins (hash / Merge And Nested Loop Join)
Oct 18, 2012I want to know how the Oracle optimizer choose joins and apply them while executing the query. So that I will insure about optimizer join before writing any query.
View 2 Replies View RelatedSQL & PL/SQL :: What Is Hash Join
Jul 12, 2012what is Hash join?how it is different from inner join?what is the sign used for inner join?(eg: like the (+) sign used for outer join)?
View 1 Replies View RelatedPL/SQL :: How To Use Hash Join
Jan 13, 2013If i have a table T1 and a table T2. Table T1 is having 100 rows and table T2 is having 20 rows. When performing a Hash join ,which table should be used to make the hash table ,the larger one or the smaller one and why ?IF the data set is too small for considerations then please conser table T1 with 10 million of rows and table T2 with 1 million of rows.
View 11 Replies View RelatedSQL & PL/SQL :: Hash Join And Nested Loops
Mar 16, 2011What is the difference between Hash join and Nested Loops in pl / sql?
View 1 Replies View RelatedHash Value Generation
Aug 21, 2012I have a question.
When and Where HASH VALUE for a given SQL statement get generated?
SQL & PL/SQL :: How Hash Is Computed
May 22, 2013Is it true that the SQL hash is computed on the SQL text only ?
View 4 Replies View RelatedPerformance Tuning :: Different SQL ID For Same HASH-VALUE?
Nov 2, 2012I see one of my SQL's which is ran by the user on a 10.2.0.3 database changing its SQL_ID after some runs even if the query is not changed a bit! However the HASH VALUE for this query remains the same.
how a same query can have different SQL_ID's but same HASH_VALUE?
Note: Statistics are not modified on the base tables of this query.
SQL & PL/SQL :: Hash Partition Table
Jun 27, 2010I am facing a problem in fetching / updating records from a customer details table having around 20 million records. The table contains around 30 fields with 'MOBILE_NO' as primary key. most of the queries are having 'mobile_no' in where clause .I am planning to hash partition that table using mobile_no column as there is no other column available which can be used for partition.
clarify whether creating hash partition on such key would increase performance of data extraction as I have read on net that hash partitioning is not effective for performance tuning.
Hash Group By Improvement?
Aug 7, 2013I see that one of my queries from an application time is spending most of its time in the hash group by. I'm running Oracle 11g with a quarter rack exadata appliance. Is there a better way to run or design this table? query:
SELECT COUNT(*)
FROM (
SELECT "DDTMDAY", "MRKTNM", "BSMNM", "BSCNM", "CLNM", "CSCDNM", "BTSID", "SECTSEQID", "BNDID", "FAID", SUM("VATTCNT"), SUM("VMBLORGCNT"), SUM("VMBLTERCNT"), SUM("VSILENTRETRYCNT"), SUM("VCUSTBLKCNT"), SUM("VAXSFCNT"), SUM("VCEBLKCNT"), SUM("VWCDBLKCNT"), SUM("VT1BHLBLKCNT"), SUM("VPWRBLKCNT"), SUM("VNONBTSEQBLKCNT"), SUM("VSFULCALLCNT"), SUM("VDRPCALLCNT"),
[code]...
SQL & PL/SQL :: Normal Join And Outer Join
Oct 19, 2013Lets say I have three tables t1 and t2 and t3.
SELECT * FROM T1;
Id
____
1
2
3
4
SELECT * FROM T2;
Id
____
1
SELECT * FROM T3;
Id
____
1
Now when data exists in T2 and T3, I want to return only the records in T1 that match the records in T2 and T3 which is basically a normal join
select t1.id from t1, t2,t3 where t1.id = t2.id and t1.id = t3.id
However when there are no records in T2 or T3, I want to return all records in T1 i.e 1,2,3,4
One way of doing that is using the not exists clause
select * from t1 where not exists ( select null from t2 where t2.Id != t1.id) and not exists ( select null from t3 where t1.Id != t3.id)
Is there a better way of doing this in sql ?
Combining Hash Cluster And Indexes
Oct 28, 2010A basic select and group by query I am optimising for my Database course has returned results that indicate it will perform better on a clustered index when returning a smaller number of rows (5% of the largest table) and on a hash clustered index when returning higher volumes (50% and 80%). I understand that it is possible to use more than one index type on a table to improve performance, but I am struggling to understand how I might establish a hash cluster and a cluster on the same table? and then use hints to drive the query down one access path or the other.
Site admin - this site is a very useful resource.
Single Table Hash Clusters
Mar 16, 2013I created a single table hash cluster like this :
create tablespace mssm datafile 'c:appmssm01.dbf' size 100m
segment space management manual;
create cluster hash_cluster_4k
( id number(2) )
size 8192 single table hash is id hashkeys 4 tablespace mssm;
-- Created a table in cluster with row size such that only one record fits one block and inserted 5 records each with a distinct key value
CREATE TABLE hash_cluster_tab_8k
( id number(2) ,
txt1 char(2000),
txt2 char(2000),
txt3 char(2000)
)
CLUSTER hash_cluster_8k( id );
[code]....
If I issue the same query after creating unique index on hash_cluster_tab(id), the execution plan shows hash access and single I/O (cr = 1).Does it mean that to have single I/o in a single table hash cluster, we have to create unique index? Won't it create additional overhead of maintaining an index?
What is the second I/O needed for in case unique index is absent?
Hash Partition On Primary Key Columns?
Jul 18, 2012I have a existing non partition table with more than 100 million records,planning to re design using Hash partition.This table doesn't has any range column to do range partitioning.
Table has 40 columns with a Primary Key on two columns (guest_sales_Id ,Version Flag). guest_sales_Id is unique for entire table but with anopther column version Flag declared as Primary key.(Version Falg will have only two distinct values in entire table)
If i do hash partition,do i need to declare on two columns which are declared ad Primary key ?If i use only guest_sales_id to declare hash prtition any issues ?
SQL & PL/SQL :: Hash Partition On Fact Table
Sep 27, 2010I created the 32 hash partition on a fact table. Based on hash parititon technique it should evenly distribute data accross the different partition.But when i analyze the table and check the distribution its not at all even.
P_Name Tabspace num_Rows
SYS_P21TBS_TBS0
SYS_P22TBS_TBS0
SYS_P23TBS_TBS0
[Code]....
Security :: How To Decrypt DBMS_CRYPTO.HASH Encrypted Value
Mar 27, 2013note we need to decrypt the data which is encrypted using dbms_crypto.hash algorithm. it is possible to decrypt dbms_crypt.hash
eg
SQL> select DBMS_CRYPTO.hash(utl_raw.cast_to_raw('Foo'), 3) FROM dual;
DBMS_CRYPTO.HASH(UTL_RAW.CAST_TO_RAW('FOO'),3)
--------------------------------------------------------------------------------
201A6B3053CC1422D2C3670B62616221D2290929
Performance Tuning :: Find SQL Using Hash Value - ORA-00060
Nov 18, 2010Getting an ORA-00060 in our database. This is the alert log:
Wed Nov 10 08:01:54 2010
Global Enqueue Services Deadlock detected. More info in file
/opt/oracle/admin/ngboot/bdump/ngboot1_lmd0_13119.trc.
This is part of the lmd file:
oprocp : (nil)
opid : 0
group lock owner : (nil)
xid : 0000-0000-00000000
dd_time : 0.0 secs
dd_count : 0
timeout : 0.0 secs
[Code] ......
How do I find the SQL causing this? I have the hash value of 3180952482. should I open up en SR as this i logged in an lmd trace?
SQL & PL/SQL :: DBMS_CRYPTO Hash A BLOB In A Union Over Dblink?
Dec 27, 2012With this table in local and remote database via a DBLink
CREATE TABLE PICTURES (
ID NUMBER(12),
PICNAME VARCHAR2(20),
PICTURE BLOB
);
How come I can get the hash of the picture column fine like this:
SELECT dbms_crypto.hash@dbLink(PICTURE, 3)from SCHEMA1.PICTURES@dbLink;
but I can't do it in a union with the local database?
SELECT dbms_crypto.hash@dbLink(PICTURE, 3)from SCHEMA1.PICTURES@dbLink
UNION
SELECT dbms_crypto.hash(PICTURE, 3)FROM SCHEMA1.PICTURES;
gives "ORA-06553: PLS-564: lob arguments are not permitted in calls to remote server"
Server Administration :: How To Calculate Number Of Hash Keys
Mar 31, 2011I was reading the documentation for oracle 11gr2, with reference to URL>.....
The following examples show how to correctly choose the cluster key and set the HASH IS, SIZE, and HASHKEYS parameters. For all examples, assume that the data block size is 2K and that on average, 1950 bytes of each block is available data space (block size minus overhead).Note that 34 hash keys are assigned for each data block
how they arrive at 34 hash keys because another portion of the document states
This space determines the maximum number of cluster or hash values stored in a data block. If SIZE is not a divisor of the data block size, then Oracle Database uses the next largest divisor.
if that is the case, then number of hash keys should be 1900/55 = 34.55 which should have rounded up to 35.
Use Range-hash Partitioning Of A Large Dimension Table
Apr 12, 2013At moment we use range-hash partitioning of a large dimension table (dimension model warehouse) table with 2 levels - range partitioned on columns only available at bottom level of hierarchy - date and issue_id.
Result is a partition with null value - assume would get a null partition in large fact table if was partitioned with reference to the large dimension.Large fact table similarly partitioned date range-hash local bitmap indexes
Suggested to use would get automatic partition-wise joins if used reference partitioningWould have thought would get that with range-hash on both dimension.
How To Sort Data
Nov 23, 2008I have the following three tables:
Buyer:
BuyerID
Name
Trans:
TransID
BuyerID
Trans_Item:
Qty
Price
BuyerID
TransID
I need to figure what buyer has bought the most things. I have a function already determines the amount each buyer has bought.
So that is done. I need to order this by buyerid. How do I sort something like that? ORDER BY and GROUP BY do not work.
SQL & PL/SQL :: Count And Sort?
Mar 10, 2010I am running this query but am not getting data that is correct.
SELECT a.prod_id, a.prod_name, a.artist_name, COUNT(*)
FROM po_my_purchase_tb a, cm_track_tb b
WHERE a.prod_id = b.prod_id and b.GNR_CD = 'GR000017' AND a.purchase_date > '10-FEB-10' AND ROWNUM<50
GROUP BY a.prod_id, a.prod_name, a.artist_name, a.buy_seq
ORDER BY COUNT(*) desc
SQL & PL/SQL :: Sort By Best Match
Jan 20, 2012Suppose I have a table in which I have first_name, last_name, dob. Now I have to fetch on the basis of first_name=some_value, last_name=some_value and dob=some_date. I want to sort it on the basis of exactly fetched values. Let me take an example-
test table contains-
first_name last_name dob
---------- --------- ----
Manu Batham 02-Feb-1988
Manu Sharma 01-Jul-1987
Avinash Pandey 03-Feb-1988
Ankit Gupta 02-Feb-1988
Manu Aggrawal 02-Feb-1988
Manu Batham 20-Jan-1985
Sikha Batham 17-Apr-1988
Now if I give parameters-
first_name='Manu'
last_name='Batham'
dob='02-Feb-1988'
then my result should be like below-
result-
first_name last_name dob
---------- --------- ----
Manu Batham 02-Feb-1988
Manu Aggrawal 02-Feb-1988
Manu Batham 20-Jan-1985
Manu Sharma 01-Jul-1987
Ankit Gupta 02-Feb-1988
Sikha Batham 17-Apr-1988
My result is based on the approach-
if matched first_name, last_name, dob --> 1st prefrence in order
if matched first_name, dob --> 2nd prefrence in order
if matched first_name, last_name --> 3rd prefrence in order
if matched last_name, dob --> 4th prefrence in order
if matched first_name --> 5th prefrence in order
if matched last_name --> 6th prefrence in order
if matched dob --> 7th prefrence in order
I designed the following query for the same-
Select first_name,last_name,dob,1 "Order" from test Where
first_name='Manu' and
last_name='Batham' and
dob=to_date('02/02/1988','dd/mm/yyyy')
union
Select a,b,c,2 from test Where
[code]......
I know that this is not the best possible solution as the table is very big and doing so many hits on that table will certainly decrease the performance.
Performance Tuning :: Create Hash Partition On Fact Tables?
Aug 5, 2010I have to create a hash partition on fact tables.. we can use temp tablespace or permanent tablespace.
View 10 Replies View RelatedServer Administration :: Partition Exchange In Hash Partitioned Table
Mar 13, 2012While trying partition exchange feature of Oracle with 2 hash partitioned tables, I come to know that I can't directly exchange partitions between 2 partitioned tables
I have two hash partitioned tables , so to move partition data from one table to another will include-
1) Exchange from partitioned table to non-partitioned table.
2) exchange from non-partitioned table to new partitioned table.
But I am not sure in which hash partition my data will go in new partitioned table (data need to be moved has single key value on basis of which tables are partitioned),
Split Value And Sort By Lastname?
Dec 11, 2008I have a field called fullname that outputs records with fullname of people.
Here is what I have when I do this sql:
Select fullname from tableOne;
John Jones
Bill Aronsen
Sam Baker
George Williams
Dave Smith
I would like to sort in order of last name but cant figure out how to do the sql:
Bill Aronsen
Sam Baker
John Jones
Dave Smith
George Williams
SQL & PL/SQL :: Sort On Multiple Columns
Jun 16, 2010how does sorting on multiple columns work
suppose my query is
select * from person order by first_name desc
and sys_person_id asc
this query works , but is this write way to sort on multiple column ?
SQL & PL/SQL :: Sort Alphanumeric Data
Nov 20, 2008I have an urgent request which is pending with the following problem.
Problem :
I have a table which contains data of various datatypes like alphanumeric,varchar and number.
Now my query is " how to sort the data of the table using alphanumeric field"
How to select the data in a required(MyRequirement) sort order.
Data
============
12.4PI1
12.4
12.2
12.4T
12.3PI1
[Code]....
afterSorting(which I am getting Now)
============
12.2
12.3PI1
12.4
12.4PI1
12.4PI10
12.4PI11
[Code]...
MyRequirement
===============
12.2
12.3PI1
12.4
12.4PI1
12.4PI2
12.4PI3
12.4PI10
[Code]..
Means it has to sort the data order by lefthand side of PI and also righthand side of PI.
Pls check the attachment if you are not getting the above data in correct order.
SQL & PL/SQL :: Trigger To Sort Out Positions
Jun 22, 2011I want a trigger i have made a software abut school system i need a trigger to sort out the positions...if total number like 100,99,98 than in positions column 1,2,3 but if total marks same like 100,100 in position column shows 1,2..i need if the marks are same than in position column also same like if marks 100,100 in position column shows 1,1
View 3 Replies View RelatedPL/SQL :: Sort Column Based On Value
Oct 17, 2012Query result gives out put like in the following order
CITY NAME
CHENNAI
DELHI
LONDON
RIO DE GENARO
How to get output in the following sort order
LONDON
CHENNAI
DELHI
RIO DE GENARO
i dont want to hardcode the column values ..it will be great if i get option to generate dynamically.