duplicate annihilator

SQL statements remove duplicate records, get duplicate records --Query a table to effectively remove duplicate records, UserID as a self-growing primary key, Roleid as a repeating field The code is as follows Copy Code SELECT MIN (UserID) as UserID, Roleid from Tmptable GROUP by RoleidSELECT Roleid from Tmptable GROUP by Roleid (COUN

In peacetime development, we often encounter data tables in the duplication of data, then how to solve it? Here are two cases of data-weight method, one, complete duplication of data to weight, two, part of the field data duplication to heavy. A completely repetitive data-weight method For full duplicate data in a table, you can use the following SQL statement. Code CreateTable "#temp" as (selectdistinct * from table name);--Create a temporary tab

For example, if column A is defined as unique and the value is 1, the following statement has the same effect, that is, if there is a a=1 in the record that is in and out, the C = C + 1 is directly updated without performing the operation of C = 3. Copy Code code as follows: Insert into table (A, B, c) VALUES (1, 2, 3) on duplicate key Update C = c + 1;1 Update table Set c = C + 1 where a = 1; Also worth mentioning is that th

There is an automatic growth column C1 in a table, at the same time, there are two health columns pointing to the other two primary key c2,c3, and suddenly one day I want to C2 and C3 together as a unique key, this time must remove the C2 and C3 of the duplicate key (because C1 can not repeat), this is the topic to be discussed today, How to remove duplicate keys in this case. In the online query about the

#tmp From Duplicate_all where C1 = 1 Go Delete Duplicate_all where C1 = 1 Go INSERT INTO Duplicate_all SELECT * FROM #tmp (2) using Row_number Copy Code code as follows: With TMP As ( Select *,row_number () over (PARTITION by c1,c2,c3 Order by (GETDATE ()) as Num From Duplicate_all where C1 = 1 ) Delete tmp where num > 1 If multiple tables have completely duplicate rows, consider combining m

field in which the index resides cannot allow null values, otherwise the replace is exactly the same as the insert.After you perform the replace, the system returns the number of rows affected, and if 1 is returned, indicating that there are no duplicate records in the table, and if 2 is returned, a duplicate record is called, and the system automatically calls the delete to delete the record, and then rec

First, the resolution of the entity duplication in the database.Entity repetition is a complete repetition: the two rows of records in the table are exactly the same. This kind of data duplication needs to delete a record, the workaround is relatively simple, the following:Use SELECT DISTINCT * FROM tablename to get a result set with no duplicate records.If the table needs to delete duplicate records (

Duplicate data may be in the following two cases: the first is that only some fields in the table are the same, and the second is that the records in the two rows are the same. 1. Deletion of duplicated data in some fields 1. query duplicate data Select Field 1, Field 2, count (*) from table name group by field 1, Field 2 having count (*)> 1 Example: Select owner from dba_tables group by owner having coun

1, look for redundant records in the table, duplicate records are based on a single field (Peopleid) to determine the select * from peoplewhere Peopleid in (select Peopleid from People GROUP by Peopleid have count (Peopleid) > 1)2, delete redundant records in the table, duplicate records are based on a single field (Peopleid) to judge, leaving only the smallest ROWID recordsDelete from peoplewhere Peopleid

Ready to be sortedFor a version upgrade of a database based on a production environment or to test the performance and impact of a new application, backup recovery, and so on, we can clone it locally from the production environment without affecting the normal use of the production database. We can do this by using the Rman duplicate method and its simple way. Unlike OS-level backups, the duplicate method g

First, error hintsWe may often encounter such an error during our code writing:1. Duplicate symbols for architecture x86_64 2.clang: error:linker command failed with exit code 1 (use-v to see invocation) Second, analysis of the cause of the errorRead the cause of the error carefully to find a few key words: "Duplicate" and "symbols".The Chinese meaning of duplicate