SQL Basics 1 (MICK)

Database and SQL

C:\PostgreSQL\9.5\bin\psql.exe -U postgres -d shop

The basic idea of ​​the database

Database (DB) : it will save large amounts of data through computer processing of data can be efficiently accessed by a set of
database management system (DBMS) : used to manage the database of the computer system
the importance of the DBMS :( text files and spreadsheets can not do)

• People can not share data
• We can not provide a large number of operations required data format
• The ability to read and write automation needs programming
• Unable to deal with unexpected incidents
  kinds of DBMS
• Hierarchical databases: Hierarchical DB
• Relational Database: Relational DB using SQL (Structured Query Language) queries
  • Relational database management system: Relational Database Management System
    • Oracle
    • SQL Server
    • DB2
    • Postgresql
    • MySQL
• Object-oriented database: Object Oriented DB
• XML database: XMLDB

• Key-value storage system: Key_Value Store

  Structure of the database

  Common RDBMS architecture of
  the client, the server, the client by calling SQL data
  tables structure
• Table: two-dimensional table consisting of rows and columns
• According to the data contents of the SQL statement returned must be in the form of two-dimensional table
• Field, recording a relational database reads and writes data in units

• Column (vertical direction) and a row (horizontal direction) intersecting grid called cell, a cell only one data input

  SQL summary

• SQL is a language for manipulating relational databases
• The type of SQL statements
  • DDL (Data Definition Language) to create or delete data stored in databases and database objects such as tables
    • CREATE: to create the database and data tables
    • DROP: delete the database and data tables
    • ALTER: modify the structure of the database and tables
  • DML (Data Manipulation Language) is used to query or change records in the table
    • SELECT: data look-up table
    • INSERT: insert new data into the table
    • UPDATE: update table data
    • DELETE: to delete the data in the table
  • DCL (Data Control Language) is used to confirm or cancel the changes to the data in the database
    • COMMIT: to confirm the changes to the data in the database
    • ROLLBACK: Cancel changes to the data in the database
    • GRANT: gives user rights
    • REVOKE: cancel the user's operating authority
• The basic rules of writing SQL
  • SQL statements with a semicolon (;) end of a SQL statement may describe the operation of a database
  • SQL statements are not case-sensitive To facilitate understanding of the Uniform Rules
    • Keyword Capitalization
    • The first letter of the table name in uppercase
    • Column name lowercase
    • Inserted into the data table is case-sensitive, the cell Gerry Computer, COMPUTER, computer is not the same
  • Notation is fixed constant
    • Dates to recommend a unified single quotes '2010-01-26' format
    • Numeric constant without filling in single quotes

    • Half-size space word need to separate or break lines

      Create a table

• Creating a database

CREATE DATABASE <数据库名>;
CREATE DATABASE shop;

• Create a table

CREATE TABLE <表名>
                    (<列名1><数据类型><该列的约束>
                     <列名2><数据类型><该列的约束>
                     <列名3><数据类型><该列的约束>
                     ...
                     <该表的约束1><该表的约束2>);
CREATE TABLE Product
                     (product_id CHAR(4) NOT NULL,
                      product_name VARCHAR(10) NOT NULL,
                      product_type VARCHAR(32) NOT NULL,
                      sale_price INTEGER ,
                      purchase_price INTEGER ,
                      regist_date DATE ,
                      PRIMARY KEY (product_id)
                     );  --Postgresql通过 \dt来查看数据库里的表 \dt <表名>来查看表的定义

• Naming Rules
  • Use only half-width letters, numbers, underscores (_) name as the database, table and column
  • The name must begin with a half-width letters
  • You can not create a database with two tables with the same name
• type of data
  • All columns must specify the data type of
    the data type indicates the type including numeric, character and date data type - INTEGER for integer storage, can not store decimal
    • CHAR string used to specify the storing fixed-length string is case-sensitive
    • VARCHAR variable to store the string used to specify a case-sensitive string - Oracle used VARCHAR2
    • DATE is used to specify the storage date
• Set constraint: In addition to data type, data stored in a column or limiting conditions added functionality
  • NOT NULL non-empty

  • PRIMARY KEY key primary (non-empty not repeated)

    Delete, and update the table

• Delete table

     DROP TABLE <表名>;
     DROP TABLE <Product>; --无法恢复           

• Update table

1. Increase Column

ALTER TABLE <表名> ADD COLUMN <列名>;
-- Oracle和MS SQL 可以不写COLUMN
-- Oracle添加多列：ALTER TABLE <表名> ADD (<列名1>,<列名2>,...);

1. Remove Columns

ALTER TABLE <表名> DROP COLUMN <列名>;
-- Oracle不用写COLUMN
-- Oracle删除多列：ALTER TABLE <表名> DROP (<列名1>,<列名2>,...); --无法恢复

1. Inserting data into the table

-- DML：插入数据
BEGIN TRANSACTION;
INSERT INTO Product VALUES ('0001','T恤衫','衣服',1000,500,'2009-09-20');
INSERT INTO Product VALUES ('0002','打孔器','办公用品',500,320,'2009-09-11');
INSERT INTO Product VALUES ('0003','运动T恤','衣服',4000,2800,NULL);
INSERT INTO Product VALUES ('0004','菜刀','厨房用具',3000,2800,'2009-09-20');
INSERT INTO Product VALUES ('0005','高压锅','厨房用具',6800,5000,'2009-01-15');
INSERT INTO Product VALUES ('0006','叉子','厨房用具',500,NULL,'2009-09-20');
INSERT INTO Product VALUES ('0007','擦菜板','厨房用具',880,790,'2008-04-28');
INSERT INTO Product VALUES ('0008','圆珠笔','办公用品',100,NULL,'2009-11-11');
COMMIT;  
-- MySQL改为：START TRANSACTION -- Oracle和DB2中不用BEGIN TRANSACTION

1. Modify the table name

ALTER TABLE Poduct RENAME TO Product; -- Oracle/PostgreSQL
RENAME TABLE Poduct TO Product; -- DB2:
sp_rename 'Poduct','Product'; -- SQL SEVER:
RENAME TABLE Poduct TO Product; --MySQL: