why use primary key

As an important mechanism for periodically cleaning up invalid data, primary key failures exist in most caching systems, and Redis is no exception. Of the many commands provided by Redis, EXPIRE, Expireat, Pexpire, Pexpireat, and Setex and Psetex

There's a thing that's been bothering me in my head, but it's not clear that it's going to hinder my progress. Do your own project demo can always use only one sheet ... So today is still learning the next foreign key hope to understand some

Directory:1. Implementation method One: the properties corresponding to the composite primary key are put together with other normal properties of the entity2. Implementation method Two: Extract the primary key attribute into a primary key class,

one, compound primary key The so-called compound primary key means that your table's primary key contains more than one field composition, and does not use an ID with no business meaning as the primary key. Like what CREATE TABLE Test ( name

Hibernate Federated primary Key mappings 1. Implement one: Combine the properties of a composite primary key with other common attributes of the entity 2. Implementation mode Two: Extract the primary key attribute into a primary key class, and the

There are three main ways of using Hibernate annotations for federated primary keys:First, the field of the Federated primary key is placed in a single class, which needs to implement the Java.io.Serializable interface and override Equals and

A Preliminary Study on the combination of primary keys and primary keys of SQL statements; a preliminary study on the primary keys of SQL statements I. Composite primary key The so-called composite primary key means that the primary key of your

The primary key and foreign key are the adhesives that organize multiple tables into a valid relational database. The primary key and foreign key design have a decisive impact on the performance and availability of the physical database. The

Oracle Primary Key usage explanation, oracleprimary Oracle/PLSQL: Primary Key Usage1 goal The example shows how to create, delete, disable, and enable a primary key. 2 preface-what is a primary key? In Oracle, a primary key indicates a single data

SQLServer sets two primary keys, and sqlserver sets the primary keyZookeeper First, a table cannot have two primary keys. However, two fields can be combined into a primary key, which is why two fields in the table sometimes have a primary key flag,