SQL Database Structured Query Language

1. Database

• Common databases

  • MySQL: Open source free database, small database.
  • Oracle: A large database of fees, Oracle's products
    
  • DB2:IBM company fee database, often used in the banking system
    
  • Sqlserver:microsoft company charges for medium-sized databases, C #,. NET and other languages are used frequently
    
  • SQLite: A small embedded database, applied to the mobile phone side

2. SQL language

• Database Structured Query Language

  • SQL is the abbreviation for Structure query Language (Structured Query language), which is a database application language that uses the relational model.

• The SQL statement is divided into the following 3 types.

  • DDL (data definition Language) Statements: Data definition statements that define different data segments, databases, tables, columns, indexes, and other database objects. The commonly used statement keywords include create, drop, alter and so on.

  • DML (data manipulation Language) statement: Data manipulation statements for adding, deleting, updating, and querying database records, and for checking data integrity. Common statement keywords include insert, delete, update, select, and so on.

  • DCL (Data Control Language) statement: A statement that controls the level of permission and access to different data segments directly. These statements define the database, table, field, user's access rights, and security level. The main statement keywords include GRANT, revoke, and so on.

SQL Database Structured Query Language