find duplicates query sql

duplicate field 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, which can be written in the SELECT clause without this column in the actual write)FourDuplicate querySELECT * FROM tablena

Use pt-query-digest to find the SQL statement that is not suitable, pt-query-digestsql Overview of pt-query-digest1. Indexes can be executed more quickly, but there must be unreasonable indexes. If you want to find those indexes t

can be only one primary key for 11 tables, and a unique index may build multiple.The 2 primary key can be used as a foreign key for other tables.3 The primary key is not nullable, and the unique index can be null. Clustered index: A directory in which data within a table is arranged according to certain rules. Because of this, there is only one focus index in a table. To this we should note that the "primary key is the focus index" is extremely wrong, is a focus on the index of a waste. (althou

Label:This article is a guide: how to find inefficient SQL statements in MySQL? This may be a problem for many people, and when MySQL uses the slow query log to locate those SQL statements that perform less efficiently, and start with the--log-slow-queries[=file_name] option, Mysqld writes a containing all execution ti

Label:I've often been asked this question repeatedly: "I have a poorly performing SQL Server." How do I find the worst performance query? “。 So in today's article there are some information and wizards that make it easy to find answers to your questions. Ask SQL server! One

Label:How to find your worst-performing SQL Server queryI've often been asked this question repeatedly: "I have a poorly performing SQL Server." How do I find the worst performance query? “。 So in today's article there are some information and wizards that make it easy to

MySQL slow query can help us optimize the efficiency of the MySQL database. The following describes how to enable MySQL slow query to find SQL statements that affect the efficiency. During website operation, the website may suddenly slow down. In general, it is related to the slow MySQL

I've often been asked this question repeatedly: "I have a poorly performing SQL Server." How do I find the worst performance query? “。 So in today's article you will be given some information guides that make it easy to find answers to your questions. Ask SQL server! One ad

/*Department parentdept departmanage Rank--------------- -------------------- ----------------------- -----------Technical Department general manager Tom 0Program Group Technical Department GiGi 1Design Group Technical Department Yoyo 1Special Group program group Yue 2*/ --Query department manager is Gigi's superior department name; with HgO as(SELECT *,0 as rank from #EnterPrise where departmanage= ' GiGi 'UNION ALLSelect h.*,h1.rank+1 from #EnterPr

Find a SQL query statement

10 million text messages to find the top 10 duplicates Analysis: For the subject, some interviewers want to use the database method to achieve: first the text into the database, and then use the SELECT statement some methods to obtain the first 10 text messages. But actually using the database is not enough to solve this condition for 5 minutes. This is because 10 million text messages even 1 seconds into

Label:I've often been asked this question repeatedly: "I have a poorly performing SQL Server." How do I find the worst performance query? “。 So in today's article there are some information and wizards that make it easy to find answers to your questions.Ask SQL server!One ad

said that he could use the Inverse thinking of the binary method to do this, for example, 2-> 4-> 8-> 16-> 32-> 64-> 100. The span is getting bigger and bigger, it may take up to 30 times. Although this method is not the desired result, it provides us with an inspiration that we can find a suitable degree. For example, if you can directly find a building and fail to return, you can save a lot of floors. Th

Title, to turn on MySQL's slow query log, you can set two items in the MySQL configuration file under [mysqld]:Log-slow-queries = D:/soft/phpnow/mysql-5.1.50/test.logLong_query_time = 1Log-slow-queries represents the log book storage location, Long_query_time indicates the execution time unit is seconds, so set up after restarting the MySQL server, query more than 1 seconds of

U.userid=ur. User_ID left joins Base_roleinfor R on R.role_id=ur. role_id) t where t.userid=t1. USERID for XML Path (")) as RoleName from (select R.role_name,u.userid,u.username,u.truename from base_userinfor u left Joi n base_userrole ur on u.userid=ur. User_ID left joins Base_roleinfor R on R.role_id=ur. role_id) T1 GROUP by Userid,truename,usernameLook at the results of the query, not what we want.It is important to pay attention to the following

"-" occurrence CHARINDEX ('-', reverse (@str)) Gets the character after the last "-" Reverse (substring (reverse (@str), 1,charindex ('-', reverse (@str))-1)) Type conversions CAST (@XX as char (20)) CONVERT (char), @XX) Cast (0 as bit) --Simple Case function Case Sex When ' 1 ' Then ' men ' When ' 2 ' then ' women ' Else ' other ' end --case search function case If sex = ' 1 ' Then ' man ' When sex = ' 2 ' Then ' women ' Else ' other ' end declaring and using variables declare @OldItemPath

With SQL statements, delete duplicates only keep one In thousands of records, there are some same records, how can you use SQL statements, delete duplicates1, look for redundant records in the table, duplicate records are based on a single field (Peopleid) to determineSELECT * from Peoplewhere Peopleid in (select Peopleid from People GROUP by Peoplei

fromVitaeGroup byPeopleid,seq having Count(*)> 1) androwID not inch(Select min(ROWID) fromVitaeGroup byPeopleid,seq having Count(*)>1) 5, find redundant duplicate records (multiple fields) in the table, and do not contain ROWID minimum recordsSelect * fromVitae awhere(A.PEOPLEID,A.SEQ)inch(SelectPeopleid,seq fromVitaeGroup byPeopleid,seq having Count(*)> 1) androwID not inch(Select min(ROWID) fromVitaeGroup byPeopleid,seq having Count(*)>1)

35. use SQL query analyzer and SQL profilerUse SQL query AnalyzerUse SQL profilerOptimize T-SQL statementSummaryIn this chapter, we will continue with the description of the pre-stored

Find the corresponding SQL statement using the PID in the operating system, and find the SQL statement using the pid.In linux, we generally use the TOP command to view the processes with the largest performance consumption. If oracle is used, we need to query the