Database Knowledge Collation

relational database knowledge-based collation:

A, relational database management system introduction:

1.1 Reasons to use the database:

1. Reduce the redundancy of storage data
2. Improved consistency of data
3. Standards that you can follow to establish a database
4. Stored data can be shared
5. Easy to maintain data integrity
6. The ability to achieve data security

1.2 Basic concepts:

1. For any database, there are three basic types of relationships between tables: one-to-one, one-to-many, many-to-many, and only three.
2. The current popular relational database server management system is: Microsoft-MS SQL Server, Oracle-oracle, IBM-DB2, open source MySQL and PostgreSQL. (has been asked in the interview).
3. SQL: is a structured Query language, a computer language for shutting down a relational database and communicating data in a database. Whether we use the Business database management system SQL Server, Oracle, DB2, MYSQL, some features are the same for RDBMS-relational database management systems.
4. The primary key (primary key) in the relational data uniquely identifies each row, and the foreign key (Forergn key) represents the association between the table and the table.

1.3SQL statement:

The SQL standard defines the operational relational database and the various techniques that contain the data, and divides the SQL statements into:

1.3.1 Data Definition Language (DDL)-Used to create, modify, and delete data structures within a database. (Note that it differs from the operating language and that it is the data structure rather than the information)

1. Create and DELETE statements for database creation and drop databases. (Delete database, table, and index with drop instead of delete)
2. Create, delete, rename, and modify statements for the table's CREATE TABLE, drop table, rename table, ALTER TABLE.
3. Creating and Deleting Indexes: CREATE index and DROP index.

1.3.2 Data Query Language (DQL):

The data query Language DQL is used to query the specified data from one or more tables in the database, and DQL contains the SQL statement that contains the SELECT statement, which we call the SELECT statement as an SQL statement.

1.3.3 Data Manipulation Language (DML)-Used to insert, delete, modify data:

1. Insert statement that inserts data into a table.
2. Update the existing Data UPDATE statement in the table.
3. Delete an existing data DELETE statement in the data table. (This knowledge point is involved in the written test)

1.3.4 Data Control Language (DCL)-Used to control access to the database:

1. Grant statement that grants access to the user.
2. The REVOKE statement that cancels the user's access rights.

Summary: The above basic things are the necessary skills for work and interview, not careless. (continued )

Database Knowledge Collation