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oracle oracle-10g asked 2 hours ago Shaunyl 36819 1 vote 2answers 98 views What is the best way to purge data from a table with minimum damage to performance? When you purge records from a database table, deleting them, you have impact on the logical and physical structure of the target table, as well as indexes and statistics. mysql asked 1 hour ago travisantonio 61 4 votes 2answers 107 views Is a weekly rebuild of indexes a good idea? We had a SQL expert suggest rebuilding our table indexes weekly
Other People Are Reading How to Remove Duplicates in Access How to Prevent Duplicate Values in a Microsoft Access Database Instructions Open your SQL command interface. You can delete duplicates by copying all distinct records to another table, then removing the old table and renaming the new table to the name of the old one
SQL FAQ - Oracle FAQ
COMMIT - save work done SAVEPOINT - identify a point in a transaction to which you can later roll back ROLLBACK - undo the modification I made since the last COMMIT SET TRANSACTION - Change transaction options like isolation level and what rollback segment to use SET ROLE - set the current active roles DML are not auto-commit. If you include the SAMPLE clause within a multi-table or remote query, you will get a parse error or "ORA-30561: SAMPLE option not allowed in statement with multiple table references"
http://javarevisited.blogspot.com/2012/12/how-to-find-duplicate-records-in-table-mysql-query-example.htmlYou can see in first query that it listed Ruby as duplicate record even though both Ruby have different phone number because we only performed group by on name. Can you please write something about DB performance tuning as well as its being repetitvely asked to me and am unable to convince a great deal as I havent really worked on such scenarios December 17, 2012 at 8:07 AM Anonymous said..
Type into the console: select count() from TheTable and select distinct from TheTable The 1st command tells you how many total records you have in the table, and the 2nd command tells you how many duplicates you have. The total count of the original table should be the difference between the number counted before the delete query and the number deleted from the table
We extensively use GROUP BY and we all know problem with GROUP BY (We should have all selected column from select clause in group by clause, other wise we cannot use group by). The problem is: the system by mistake inserted duplicate data in R2-R5 (R1 is PK assuem autonumber) and in one of these duplicates R6 and R7 are also filled
To create the sample table and populate it with data, execute the following script: CREATE TABLE Customers ( ID INT PRIMARY KEY CLUSTERED, FirstName VARCHAR(20), LastName VARCHAR(20) ) INSERT INTO Customers VALUES (1, 'Bob', 'Brown') INSERT INTO Customers VALUES (2, 'Jim', 'Jones') INSERT INTO Customers VALUES (3, 'Jim', 'Jones') INSERT INTO Customers VALUES (4, 'Jim', 'Jones') INSERT INTO Customers VALUES (5, 'Bob', 'Brown') INSERT INTO Customers VALUES (6, 'Pam', 'Penny') Finding the duplicates is relatively simple. OPEN DuplicateCursor FETCH NEXT FROM DuplicateCursor INTO @FirstName, @LastName, @Count The cursor will process every row from the temporary table within a WHILE loop
select * from mytable union select * from mytable, thsi query returns the exact records, and i guess we can use this data to build a new table or replacing the previous one. I need to get rid of the duplications, meaning that when names are shown more than once for a given month and year, I only want one of the duplicated intervention records to show up
sql - removing duplicate rows from a table in DB2 in a single query - Stack Overflow
In order to be able to use a fullselect as the target for a delete clause, it has to match the rules for a deletable view (see "deletable view" under the notes section)
Remove duplicate records from SQL tables - CodeProject
Assuming that duplicate records might have different fields other than the Primary Key, we will use the MAX aggregate function to select records with maximal values in all fields. License This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL) Share email twitter facebook linkedin reddit google+ About the Author Eugene Ochakovsky Chief Technology Officer Patrol-IT United States No Biography provided You may also be interested in..
How to delete duplicate records using SQL
Delete duplicate records Delete Duplicate Records using SQL By duplicate record I mean that every field in one record is identical to every field in a different record, i.e. To check that you have duplicate records in your table do the following: select count(*) from MyTable and select distinct * from MyTable unfortunately SQL does not permit a select count(distinct)
Remove Duplicate Rows from a Table in SQL Server - CodeProject
Easiest way to delete more than one duplicate row from a table in SQL Server Introduction Most of the times, we use primary key or unique key for preventing insertion of duplicate rows in SQL Server. Is it too complicated? History 16th February, 2011: Initial post License This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL) Share email twitter facebook linkedin reddit google+ About the Author Sadeque Sharif Software Developer Meridian Group Bangladesh I am: Manager (IT) at Meridian Group
Result set after the usage of ranking function will look as below with all ranks defined 1 for unique values and all duplicates with values greater than 1
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