unique reference number

Key differs from primary keyKey is usually the index synonym. If the keyword attribute primary key is given in the column definition, then primary key can also be specified as key only. The purpose of this is to be compatible with other database

Unique indexIf the primary key is not set to a clustered index when it is created, it must be a unique nonclustered index. In fact, the unique index, the name Incredibles, is that it requires the value on that column to be unique. A unique index

clustered index, nonclustered index, nonclustered unique indexWe all know that establishing an appropriate index can improve query speed and optimize queries. First, whether a clustered or nonclustered index is a B-tree structure . The

clustered index, nonclustered index, nonclustered unique indexWe all know that establishing an appropriate index can improve query speed and optimize queries. First, whether a clustered or nonclustered index is a B-tree structure . The

Clustered index, nonclustered index, nonclustered unique indexWe all know that establishing an appropriate index can improve query speed and optimize queries. First, whether a clustered or nonclustered index is a B-tree structure . The

Important:(1) If SQL is created without specifying a type then the default nonclustered index(2) Clustered and nonclustered indexes can have duplicate records, and unique indexes cannot have duplicate records.(3) The primary key defaults to a

Python uses the current time and random number to generate a unique number. python current time This example describes how Python uses the current time and random number to generate a unique number. We will share this with you for your reference.

A field that defines a unique constraint cannot contain duplicate values, and you can define a unique constraint for one or more fields. Therefore, aUNIQUE can be defined at the field level or at the table level, and the field on the uniqued

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This article mainly describes how Python uses the current time, random numbers to produce a unique number of methods, involving Python time and random numbers related operations skills, the need for friends can refer to the following This example