在学习Spss统计分析、EA画 实体 关系 图、PowerDesigner画 数据库 模型图等时,苦于找不到一个好的实例。由于实际工作中项目使用的表结构属于公司的商业保密内容,且在和大家交流时,其结构大家也不熟悉;而使用简单创建的Teacher、Student、Class等数据模型
在学习Spss统计分析、EA画实体关系图、PowerDesigner画数据库模型图等时,苦于找不到一个好的实例。由于实际工作中项目使用的表结构属于公司的商业保密内容,且在和大家交流时,其结构大家也不熟悉;而使用简单创建的Teacher、Student、Class等数据模型时,建表、录数据也是一个麻烦事;使用SqlServer的示例数据库正好,大伙都熟悉,又是现成的。
很多书籍、教程都使用Northwind数据库作为模型,但我一直对它不甚了解,今天特意下载后了解了一下,现在简单的记录下笔记,以后依次进行Spss等的学习。
实体关系(E-R)说明:
该实例的模型包含企业员工(Employee)、客户(Custom)、产品(Product)和订单(Order)四部分,大致为客户向企业员工订购产品。
(1)员工Employee:
包括Region(东西南北四个地区)和Territory(区域、城市)以及Employee(员工),Territory属于Region,但是Employee和Territory的关系式关联而非属于,即为某个员工可以关联多个区域,好比张三即在财务部又在行政部一样。
1 Eastern
2 Western
3 Northern
4 Southern
(2)客户Custom
(3)产品Product
产品进行了分类,所有有Category,此外同一名称的产品,可能存在多个供应商Supplier,不同供应商有不同的单价等信息。
(4)订单Order
一个订单下有多个产品,然后使用某一家物流进行配货。
对应于该实体关系,数据库的设计,结构为:
其中员工表中有个自身关联,ReportTo为员工的直接领导,关联EmployeeID字段(领导也是公司员工嘛)。
理清了数据结构,然后就可以对其进行分析等处理了。

MySQL uses a GPL license. 1) The GPL license allows the free use, modification and distribution of MySQL, but the modified distribution must comply with GPL. 2) Commercial licenses can avoid public modifications and are suitable for commercial applications that require confidentiality.

The situations when choosing InnoDB instead of MyISAM include: 1) transaction support, 2) high concurrency environment, 3) high data consistency; conversely, the situation when choosing MyISAM includes: 1) mainly read operations, 2) no transaction support is required. InnoDB is suitable for applications that require high data consistency and transaction processing, such as e-commerce platforms, while MyISAM is suitable for read-intensive and transaction-free applications such as blog systems.

In MySQL, the function of foreign keys is to establish the relationship between tables and ensure the consistency and integrity of the data. Foreign keys maintain the effectiveness of data through reference integrity checks and cascading operations. Pay attention to performance optimization and avoid common errors when using them.

There are four main index types in MySQL: B-Tree index, hash index, full-text index and spatial index. 1.B-Tree index is suitable for range query, sorting and grouping, and is suitable for creation on the name column of the employees table. 2. Hash index is suitable for equivalent queries and is suitable for creation on the id column of the hash_table table of the MEMORY storage engine. 3. Full text index is used for text search, suitable for creation on the content column of the articles table. 4. Spatial index is used for geospatial query, suitable for creation on geom columns of locations table.

TocreateanindexinMySQL,usetheCREATEINDEXstatement.1)Forasinglecolumn,use"CREATEINDEXidx_lastnameONemployees(lastname);"2)Foracompositeindex,use"CREATEINDEXidx_nameONemployees(lastname,firstname);"3)Forauniqueindex,use"CREATEU

The main difference between MySQL and SQLite is the design concept and usage scenarios: 1. MySQL is suitable for large applications and enterprise-level solutions, supporting high performance and high concurrency; 2. SQLite is suitable for mobile applications and desktop software, lightweight and easy to embed.

Indexes in MySQL are an ordered structure of one or more columns in a database table, used to speed up data retrieval. 1) Indexes improve query speed by reducing the amount of scanned data. 2) B-Tree index uses a balanced tree structure, which is suitable for range query and sorting. 3) Use CREATEINDEX statements to create indexes, such as CREATEINDEXidx_customer_idONorders(customer_id). 4) Composite indexes can optimize multi-column queries, such as CREATEINDEXidx_customer_orderONorders(customer_id,order_date). 5) Use EXPLAIN to analyze query plans and avoid

Using transactions in MySQL ensures data consistency. 1) Start the transaction through STARTTRANSACTION, and then execute SQL operations and submit it with COMMIT or ROLLBACK. 2) Use SAVEPOINT to set a save point to allow partial rollback. 3) Performance optimization suggestions include shortening transaction time, avoiding large-scale queries and using isolation levels reasonably.


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