08. Delete duplicate massive data

There are two types of repeated data: one is a completely repeated record, that is, the values of all fields are the same; the other is a record with some field values repeated. 1. Deleting completely duplicated records data is usually caused by the absence of a unique primary key constraint. Test data: duplicate_allduplicate_all (c1int, c2int, c3var

There are two types of repeated data: one is a completely repeated record, that is, the values of all fields are the same; the other is a record with some field values repeated. 1. delete data that is completely duplicated in a record. This is usually caused by the absence of primary key/unique key constraints. Test data:) duplicate_all (c1 int, c2 int, c3 var

There are two types of repeated data: one is a completely repeated record, the Hong Kong server, that is, the values of all fields are the same; the other is a record with some field values repeated.

1. delete completely Repeated Records
Completely duplicated data is usually caused by the absence of primary key/unique key constraints.
Test data:

) Duplicate_all (c1 int, c2 int, c3 varchar (100) duplicate_all, website space, U.S. Server