data deduplication

. Rows.Add (_DR. ItemArray); Console.WriteLine ("--------------------table with duplicate data originally----------------------"); _dt. AsEnumerable (). ToList (). ForEach (M={Console.WriteLine (m["ID"]. ToString () +" "+ m["name"]. ToString () +" "+ m["Address"]. ToString ()); }); Console.WriteLine ("--------------------Remove the duplicate table----------------------"); var_compresult = _dt. AsEnumerable (). D

name,address, which requires the result set to be unique for both fieldsSelect Identity (int,1,1) as Autoid, * into #Tmp from TableNameSelect min (autoid) as autoid into #Tmp2 from #Tmp Group by name,autoidSELECT * from #Tmp where autoid on (select Autoid from #tmp2) The last select is the result set that name,address not duplicate (but one more autoid field that can be written when actually writing Omit this column in the SELECT clause) (iv) Duplication of queriesSELECT * FROM tablename where

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In the table, duplicate values may be included. That's not a problem, but sometimes you might want to just list different values (distinct). Keyword DISTINCT is used to return only different values.Table A:Example 1Select distinct name from AThe following results are performed:Example 2Select DISTINCT name, ID from AThe following results are performed:is actually based on "Name+id".Example 3: StatisticsSelect COUNT (distinct name) from A; --The number of the table name to go back to, SQL Server

1, use distinct to weight (suitable for querying the total number of the whole table)There are multiple schools + teachers to contribute, need to count the total number of authorsSelectcount (author)As total from files each author has a lot of contributions, there are duplicate records here. Selectdistinctauthor from files;It is possible that the names of teachers in both schools are the same, and only one error is counted. SelectdistinctAuthor,sid the combined unique value of the From files sta

and truncate carefully, especially when there is no backup. Otherwise, it's too late to cry.6. On the use, want to delete some data rows with delete, note with the WHERE clause. The rollback segment should be large enough. If you want to delete a table, delete all of the data by dropping it to keep the table. If it is unrelated to the transaction, use truncate. If it is related to a transaction, or if you

// Define an array to store the results after deduplication$ Result = array ();// Read the uid list file$ Fp = fopen('test.txt ', 'r ');While (! Feof ($ fp )){ $ Uid = fgets ($ fp );$ Uid = trim ($ uid );$ Uid = trim ($ uid ,"");$ Uid = trim ($ uid ,"");If ($ uid = ''){ Continue;} // Use uid as the key to check whether the value existsIf (empty ($ result [$ uid]){ $ Result [$ uid] = 1;} }Fclose ($ fp );// Sa

Tags: mongodbRecently wrote a crawler tool, the data stored in the Web site MongoDB, because the data are duplicated, so I set up the database when the index, the following is my step, the set name is Drugitem,Here is the collection:I want to create a unique index for the name field because I want to ensure that name is not duplicated:In this way I run the program to find that the

); - //registering a merge class $Job.setcombinerclass (Reduce.class); the //Register Reducer Class theJob.setreducerclass (Reduce.class); the //registering the output format class theJob.setoutputkeyclass (Text.class); -Job.setoutputvalueclass (Text.class); in //setting the input and output path theFileinputformat.addinputpath (Job,NewPath (otherargs[0])); theFileoutputformat.setoutputpath (Job,NewPath (otherargs[1])); About the //Run the

Label:How is duplicate data removed from the Oracle database? When working with data tables, there are often duplicate data, so how do you delete them? Let's talk about removing data duplication from Oracle databases. There are two ways we are going to talk today.First, according to rowID come and go heavy.We all know

Label:In a database table, duplicate values may be included. That's not a problem, but sometimes you might want to just list different values (distinct). Keyword DISTINCT is used to return only different values. Table A: 1. Acting on a single rowSelect distinct from A The following results are performed: Acting on multi-column Example 2.1Select distinct from A The following results are performed: In fact, it is the same way that access and SQL Server support it, depending on the name and ID t

Business Requirements:A table has the Id,n1,n2,n3 field, which is a new empty table,Table B has id,n1,n2,n3,n4,n5 fields, such as old tables containing data,Now the record of the N1,N2,N3 combination in B table is re-imported into a table, and a table primary key is also entered valueScenario: The records of B table after the query to go to the weight, while the results of the records are numbered, the sequence number as a table to insert the ID value

var New Array (); if ($ ("input[name= ' type ']"). val ()! = "") {= $ ("input[name= ' type ')"). Val (). Split ("," ); if (SelectedValue! = "" $.inarray (SelectedValue, valuearr) = =-1) { valuearr.push (selectedvalue); } $ ("input[name= ' type ']"). Val (Valuearr.sort (). join ());JavaScript strings are transferred to and from arrays, and

main field = @idFetch cur_rows into @id, @maxEndClose Cur_rowsSET ROWCOUNT 0Method TwoThere are two meanings of duplicate records, one is a completely duplicate record, that is, all fields are duplicated records, and second, some key fieldsDuplicate records, such as the Name field, and the other fields may not be repeated or repeated can be ignored.1, for the first kind of repetition, easier to solve, usingSELECT DISTINCT * from TableNameYou can get a result set with no duplicate records.If the

Tags: unique values Group Stat author A10 sage how multiple artReference: Http://blog.sina.com.cn/s/blog_6c9d65a10101bkgk.htmlHttp://www.jb51.net/article/39302.htm 1, use distinct to weight (suitable for querying the total number of the whole table)There are multiple schools + teachers to contribute, need to count the total number of authorsSelect COUNT (author) as Total from files each author has a lot of contributions, there are duplicate records here. Select distinct author from files; It is

Label:CREATE TABLE #tp(Headerno VARCHAR (10),Machineno VARCHAR (10),Descrption NVARCHAR (20),Artno VARCHAR (20),Qty INT,Repartno varchar (20),Repqty INT) INSERT INTO #tp SELECT ' HD01 ', ' 0101520 ', N ' battery problem ', ' 102020 ', 2, ' 102020 ', 2INSERT INTO #tp SELECT ' HD01 ', ' 0101520 ', N ' battery problem ', ' 101010 ', 2, ' 202020 ', 2INSERT INTO #tp SELECT ' HD01 ', ' 0101520 ', N ' battery problem ', ' 126888 ', 2, ' 102020 ', 2INSERT INTO #tp SELECT ' HD02 ', ' 01012221 ', N ' d mo

--Under the sql2005, sql2000 can notCREATE TABLE TB (ID int,name varchar (4))Insert TB Select 1, ' AA 'UNION ALL Select 1, ' AA 'UNION ALL Select 2, ' BB 'UNION ALL select 3, ' BB 'UNION ALL Select 4, ' CC 'UNION ALL Select 1, ' AA 'UNION ALL Select 4, ' CC 'Delete a From(select Id,name,rn=row_number () over (partition by id,name order by ID) from TB) a where rn>1SELECT * FROM TBOriginal: http://blog.csdn.net/hzvcan/article/details/4862927SQL Server Data