但在oracle和mongodb数据库中有单独的字段判断唯一性;所以设计中没有自增长字段方式(mysql和mssql都有);并且也不提倡用自增长
在数据库设计原理中;自增长字段的目的是为了unique的索引来判断每条记录唯一性;同时保证大数据库量的时候的查询速度。
但在Oracle和mongodb数据库中有单独的字段判断唯一性;所以设计中没有自增长字段方式(mysql和mssql都有);并且也不提倡用自增长字段设计表结构。
不过经常用习惯这种方式的程序员;oracle和mongodb数据库也可以实现类似的功能;oracle中有sequence方式。
那我们也可以试试在mongodb数据库中实现自增长字段模式;就是模仿一下oracle中有sequence方式。
1:在mongodb数据库中建立一个名为:sequence的collection;
2个field:coll_name(记录其它collection名字)和cnt(其它collection的自增长字段最大序号)。
2:java代码:
//得到用户表的sequence 自增长id
private static int getSequence(String tableName){
DBCollection table = conn.getDb().getCollection("sequence");
DBObject query = new BasicDBObject();
query.put("coll_name", tableName);
DBObject newDocument =new BasicDBObject();
newDocument.put("$inc", new BasicDBObject().append("cnt", 1));
DBObject ret = table.findAndModify(query, newDocument);
if (ret == null){
return 0;
}else{
return (Integer)ret.get("cnt") + 1;
}
}
//新增用户
public static void addUser(UserInfo user){
int id = getSequence("admin_user");
if(id != 0){
DBCollection table = conn.getDb().getCollection("admin_user");
DBObject query = new BasicDBObject();
query.put("id", id);
query.put("name", user.getName());
query.put("e_mail", user.geteEmail());
query.put("passwd", user.getPassword());
query.put("is_del", false);
query.put("create_time", user.getCreateTime());
table.insert(query);
}
}

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MySQL is suitable for beginners to learn database skills. 1. Install MySQL server and client tools. 2. Understand basic SQL queries, such as SELECT. 3. Master data operations: create tables, insert, update, and delete data. 4. Learn advanced skills: subquery and window functions. 5. Debugging and optimization: Check syntax, use indexes, avoid SELECT*, and use LIMIT.

MySQL efficiently manages structured data through table structure and SQL query, and implements inter-table relationships through foreign keys. 1. Define the data format and type when creating a table. 2. Use foreign keys to establish relationships between tables. 3. Improve performance through indexing and query optimization. 4. Regularly backup and monitor databases to ensure data security and performance optimization.

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SQL is used to interact with MySQL database to realize data addition, deletion, modification, inspection and database design. 1) SQL performs data operations through SELECT, INSERT, UPDATE, DELETE statements; 2) Use CREATE, ALTER, DROP statements for database design and management; 3) Complex queries and data analysis are implemented through SQL to improve business decision-making efficiency.

The basic operations of MySQL include creating databases, tables, and using SQL to perform CRUD operations on data. 1. Create a database: CREATEDATABASEmy_first_db; 2. Create a table: CREATETABLEbooks(idINTAUTO_INCREMENTPRIMARYKEY, titleVARCHAR(100)NOTNULL, authorVARCHAR(100)NOTNULL, published_yearINT); 3. Insert data: INSERTINTObooks(title, author, published_year)VA


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