MySQL's most basic select statement

1. Basic statement

（1） View all databases

show databases;

（2） Create your own database

create database Database name

（3） Use your own database

use Database name

（4） View all tables in a library

show tables from Database name

（5） Create a new table

create table The name of the table ( Field name data type ,

Field name data type );

explain ： If it is the last field , Then add a comma , Because the comma is used to separate each field .

（6） View the data of a table

select * from Database table name ;

（7） Add a record

insert into The name of the table values( List of values );

 （8） View the table creation information

show tables;

（9） View database creation information

show create database Database name \G

（10） Delete table

drop table The name of the table ;

（11） Delete database

drop database Database name

（12） Import an existing data table , The data table

One .source The full pathname of the file

explain ： Can only be used at the command prompt

Two . Tools based on specific graphical interfaces can import data

explain ： I'm using SQLyog,Windows The system is case insensitive

however SQLyog Keyword functions in are capitalized , So the following statements will be capitalized

2. The most basic SELECT sentence

（1）SELECT Field 1, Field 2,.....FROM Table name ;

dual: false （ false ） surface         *： All fields in the table （ Or column ）

（2） Full name of the column

as： Full name （alias（ Alias ））, It can be omitted

Column aliases can use a pair of " " Lead up , Do not use ' '

（3） Remove duplicate lines

SELECT DISTINCT Field FROM Table name ;

（4） Null values participate in the operation

Null value ：null

null Not equal to 0,' ','null'

Null values participate in the operation ： The result must also be empty

Solutions to practical problems ： introduce IFNULL

（5） mark of emphasis

SELECT * EROM 'order';// Same name as keyword

（6） Query constant

Columns such as ：SELECT 'huyangyang',123,emplovee_id,last_name

FROM employees;

（7） Display table structure

DESCRIBE Table name ;

Shows the details of the fields in the table

or DESC

（8） Filtering data

SELECT * FROM Table name WHERE Field = 'huyangyang';

The query field is 'huyangyang' Employee information