Common basic database operations

First, the data definition statements (DDL)

1. Create a database

　1) Syntax: create database if not exists database name

　2) database name naming requirements:

• The first character must be uppercase or lowercase letters, or special characters underscore _, @, #;
• Subsequent characters can be letters, numbers, @, $, symbols or numbers underlined;
• Identifier can not do RDBMS reserved words;
• Do not allow embedded spaces or other special characters.

2, modifying the database character set: alter database table name character set = UTF-8

3, delete the database: drop database database name

4, create a table: create table table name (
    Column Name Data Type Constraints,
   Column Name Data Type Constraints
)

5, the operation of common data table

• Deleting a table // drop ---> DROP TABLE tongxun;
• Rename the table // rename to | as: ALTER TABLE tongxun RENAME TO tongxun1;
  or ALTER TABLE tongxun1 RENAME AS tongxun;
• Copy a table structure // like: CREATE TABLE tongxun LIKE tongxunlu;
• Copy a table structure and data // as (select * from the old table): CREATE TABLE tongxun AS (SELECT * FROM tongxunlu);
• Add a new column to the table // add column a new column name data type: ALTER TABLE tongxunlu ADD COLUMN scode1 INT auto_increment PRIMARY KEY;
• To delete a table // alter table drop column column: ALTER TABLE tongxunlu DROP COLUMN scode1;
• Modify the column names and types // change column column column names old new column name data type: ALTER TABLE tongxunlu CHANGE COLUMN scode school VARCHAR (10);

Second, the data manipulation statements (DML)

1, insert data

• Insert data insert into the table (a column name, a column name 2 ...) values ​​(value 1, value 2 ...): INSERT INTO Students (sname, saddress, sgrade, semail, ssex) VALUES ( 'John Doe', 'Chengdu', 6, '123 @ qq.com', 0);
• Selecting students from the table insert new table corresponding to the content in TongXunLu: INSERT INTO TongXunLu (name, address, email) SELECT sname, saddress, semail FROM Students;
• Use multiple insert statement batch execution: insert into table (1 column names, column names, 2 ...) values ​​(1 values ​​list, a list of values ​​... 2)

2, modify the data

• update table set where the initial content of the modified content: UPDATE students SET sname = "John Doe" WHERE sname = 'John Doe';

3, delete data

• DELETE FROM table name WHERE deletion condition: DELETE FROM students WHERE sname = 'John Doe';
• To delete all the data in the table: DELETE FROM students;