1. Data storage 3 Stages 1. Manual Management Phase 2. File system Phase 3. Database system phase Database composition 1. The database consists of several tables, and the table consists of several fields of 2. The tables of the relational database are two-dimensional table 2. Database generics (requirements to create a database) 1. First Paradigm (1NF) : The minimum required table for the design database cannot have duplicate fields, and each field cannot be split 3. Database technology composition 1. Database system 2.SQL statements 3. Database access Technology 4.sql language classification 1.DDL (data definition Language): Mainly used to create tables, views, indexes, triggers, etc. These include create (creating table), Alter (modify table), Drop (delete table) statement 2.DML (Database manipulation language): Mainly used for inserting (select), deleting (delete), modifying (Updata), querying (select) data. 3.DCL (Data Control Language): Primarily used to control user permissions. This includes the grant (add permissions to the user) statement and the REVOKE (revoke user rights) statement 5. Database access technology 1. Only the SQL statements in the technology application will take effect 2. Different language database access technologies are not the same. such as early Odbc,c#aod.net,java use JDBC to access the database. When you use these database access technologies, you must install the appropriate drivers separately. 3.ODBC Technology: Provides a common interface for accessing different relational databases. With an interface provided by ODBC, an application can connect to a database. Then execute the SQL language to manipulate the data in the database 4. ODBC access MySQL: You must install the driver connector/odbc5.php Access MYSQL:PHP5 to start providing the Mysqli interface. PHP can access the database through the MySQL function module and the MYSQLI interface 6. Database data type
