A review of some knowledge points in the database

1. Some knowledge points

The Mysql.exe path (D:\program files\wamp\bin\mysql\mysql5.5.20\bin) can be added to the environment variable path in the system properties of the computer so that MySQL can be used in any directory. For example: input the MySQL system in CMD can be identified;

A database is made up of many tables, and you can use keys as a reference between tables.

2. Some of the commands and their use

A) Create the database: creation databases Suyd;

b) View the database that exists in the system: show databases;

c) Switch the database, the default current operation in this library: use Suyd;

d) View the tables that exist in the database suyd: show tables;

e) Creating tables: Create table users (ID int not NULL auto_increment primary key, username char (+) NOT null default ', PASSW Ord varchar (+) NOT null default ", age int. NOT NULL default 0, sex char (4) is not null default", email varchar (+) not Nu ll default "); (there is a point in quotation marks) '

f) View the created table: show tables;

g) View table users ' specific structure: desc users;

h) View the statement creating Table users: show create table users;

i) operation of the table

　　　　Insert : INSERT into users (IDs, username, password, age, sex, email) VALUES (' 1 ', ' suyd ', ' 123456 ', ' A ', ' Girl ', ' [email Protected] ');

Query table information for users: SELECT * from users;

　　　　modified : Update users set username = ' Su ' where id = 2;

Modify multiple values at the same time: Update users set age = n, sex = ' girl ';

Modify multiple values for a person at the same time: Update users set age = 1, sex = ' girl ' where-id = +;

Delete : Delete from users where id = 1;

Enquiry

Querying the table for all cases: SELECT * from users;

Query the case of an item in the table: Select ID, username from users;

To query the condition of an item in a table according to a requirement:

Select ID, username, age+10 as age10 from users;

Select ID, username, age from the users where age > 10;

j) Delete the entire table or library:

drop table users;

Drop database Suyd;

A review of some knowledge points in the database