Processing of duplicate data in a table

The SQL statement for querying and deleting duplicate data MySQL query columnName contains duplicate data, and the largest id is retained. SELECTMAX (id) ASid, columnName, COUNT (columnName) AScountNumberFROMtableNameGROUPBYcolumnNameHAVINGcountNumber1ORDERBYcountNumberDESC; Delete colum

The SQL statement for querying and deleting duplicate data MySQL query columnName contains duplicate data, and the largest id is retained. Select max (id) AS id, columnName, COUNT (columnName) AS countNumberFROM tableNameGROUP BY columnNameHAVING countNumber 1 order by countNumber DESC; Delete colum

SQL statement for querying and deleting duplicate data MySQL

Query repeated data in columnName and retain the largest id. Select max (id) AS id, columnName, COUNT (columnName) AS countNumberFROM tableNameGROUP BY columnNameHAVING countNumber> 1 order by countNumber DESC; Delete repeated columnName data and retain the smallest id. DELETE tableName t1FROM tableName t1, (SELECT min (id) id, columnName FROM tableName group by columnName having count (1)> 1) t2WHERE t1.columnName = t2.columnNameAND t1. id> t2.id;