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Count duplicates records in MySQL table?
You can use if() from MySQL to count duplicate records. The syntax is as follows −
SELECT yourColumnName, COUNT(*) AS anyVariableName, IF ( COUNT(*)>1,"Duplicate Records", "Not Duplicate records") as anyVariableName FROM yourTableName group by yourColumnName;
To understand the above syntax, let us create a table. The query to create a table is as follows −
mysql> create table DuplicateRecords -> ( -> Id int NOT NULL AUTO_INCREMENT, -> Name varchar(30), -> PRIMARY KEY(Id) -> ); Query OK, 0 rows affected (0.82 sec)
Insert some records in the table using insert command. The query is as follows −
mysql> insert into DuplicateRecords(Name) values('Carol'); Query OK, 1 row affected (0.81 sec) mysql> insert into DuplicateRecords(Name) values('John'); Query OK, 1 row affected (0.17 sec) mysql> insert into DuplicateRecords(Name) values('Sam'); Query OK, 1 row affected (0.19 sec) mysql> insert into DuplicateRecords(Name) values('John'); Query OK, 1 row affected (0.17 sec) mysql> insert into DuplicateRecords(Name) values('Sam'); Query OK, 1 row affected (0.11 sec) mysql> insert into DuplicateRecords(Name) values('Sam'); Query OK, 1 row affected (0.20 sec) mysql> insert into DuplicateRecords(Name) values('John'); Query OK, 1 row affected (0.12 sec) mysql> insert into DuplicateRecords(Name) values('Carol'); Query OK, 1 row affected (0.14 sec) mysql> insert into DuplicateRecords(Name) values('Carol'); Query OK, 1 row affected (0.10 sec) mysql> insert into DuplicateRecords(Name) values('Mike'); Query OK, 1 row affected (0.14 sec)
Display all records from the table using select statement. The query is as follows −
mysql> select *from DuplicateRecords;
The following is the output −
+----+-------+ | Id | Name | +----+-------+ | 1 | Carol | | 2 | John | | 3 | Sam | | 4 | John | | 5 | Sam | | 6 | Sam | | 7 | John | | 8 | Carol | | 9 | Carol | | 10 | Mike | +----+-------+ 10 rows in set (0.00 sec)
Here is the query to count the duplicate records from the table −
mysql> SELECT Name, COUNT(*) AS Repetition, IF (COUNT(*)>1,"Duplicate Records", "Not Duplicate records") as IsDuplicateRecordsOrNot -> from DuplicateRecords group by Name;
The following is the output −
+-------+------------+-------------------------+ | Name | Repetition | IsDuplicateRecordsOrNot | +-------+------------+-------------------------+ | Carol | 3 | Duplicate Records | | John | 3 | Duplicate Records | | Sam | 3 | Duplicate Records | | Mike | 1 | Not Duplicate records | +-------+------------+-------------------------+ 4 rows in set (0.00 sec)
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