MySQL learning record (3)

1. Update of data

UPDATE < Table name > 

SET < Name > = < expression > [, < Name 2>=< expression 2>...]; 

WHERE < Conditions >;

--  Optional , It's very important .

ORDER BY  Clause ; -

- Optional  LIMIT  Clause ; -- Optional 
--  Modify all registration times ( Here we should connect them to make a sentence ）
UPDATE product
   SET regist_date = '2009-10-10';  
--  Only modify the unit price of some goods 
UPDATE product
   SET sale_price = sale_price * 10
 WHERE product_type = ' Kitchenware '; 
--WHERE Is the condition , Select the desired operation object that meets the conditions . 

UPDATE= to update , Use UPDATE When setting WHERE Conditions , Otherwise, it is the modification of the overall situation .

-- Single column update 
-- take ID by 008 The date of the product of is changed to null NULL
--  Number the item as 0008 The data of （ Ball pen ） The registration date of is updated to NULL  
UPDATE product
   SET regist_date = NULL
 WHERE product_id = '0008'; 

-- Multi column update 
UPDATE product
   SET sale_price = sale_price * 10,
       purchase_price = purchase_price / 2
 WHERE product_type = ' Kitchenware ';  

Only unset Only columns with non empty constraints and primary key constraints can be cleared to NULL.** If the column with the above constraints is updated to NULL, Will report a mistake .

2.INSERT sentence （ Insert ）

Create a new table first productins

CREATE TABLE productins
(product_id    CHAR(4)      NOT NULL,
product_name   VARCHAR(100) NOT NULL,
product_type   VARCHAR(32)  NOT NULL,
sale_price     INTEGER      DEFAULT 0,
purchase_price INTEGER ,
regist_date    DATE ,
PRIMARY KEY (product_id)); 

INSERT Basic syntax ：INSERT INTO < Table name > ( Column 1, Column 2, Column 3, ……) VALUES ( value 1, value 2, value 3, ……);

--  Contains a list of columns 
INSERT INTO productins (product_id, product_name, product_type, 
sale_price, purchase_price, regist_date) VALUES ('0005', ' pressure cooker ', ' Kitchenware ', 6800, 5000, '2009-01-15');
--  Omit the list 
INSERT INTO productins 
VALUES ('0005', ' pressure cooker ', ' Kitchenware ', 6800, 5000, '2009-01-15');

When inserting a full column , You can omit column names , Directly write the corresponding data to be inserted  

--  Multiple lines INSERT （ DB2、SQL、SQL Server、 PostgreSQL  and  MySQL Multi line insertion ）
INSERT INTO productins VALUES ('0002', ' Punch ', 
' Office Supplies ', 500, 320, '2009-09-11'),
('0003', ' motion T T-shirt ', ' clothes ', 4000, 2800, NULL),
('0004', ' kitchen knife ', ' Kitchenware ', 3000, 2800, '2009-09-20');  
-- Insert multiple lines with （） and , Segmentation 

INSERT The statement wants to assign... To a column NULL When the value of , Can be directly in VALUES Clause in the list of values NULL. Want to insert NULL Columns must not be set NOT NULL constraint .

INSERT INTO productins (product_id, product_name, product_type, 
sale_price, purchase_price, regist_date) VALUES ('0006', ' Fork ', 
' Kitchenware ', 500, NULL, '2009-09-20');  

You can also insert default values into the table （ Initial value ）. You can create a table by CREATE TABLE Set... In the statement DEFAULT Constraints to set default values .

Join in DEFAULT 0, The default value is 0

CREATE TABLE productins
(product_id CHAR(4) NOT NULL,
（ A little ）
sale_price INTEGER
（ A little ）	DEFAULT 0, --  The default value of the sales unit price is set to 0;
PRIMARY KEY (product_id)); 

4. Copy the data

Use INSERT … SELECT Statement to copy data from other tables .

--  Copy the data in the item table to the item table 
INSERT INTO productocpy (product_id, product_name, product_type, sale_price, purchase_price, regist_date)
SELECT product_id, product_name, product_type, sale_price, 
purchase_price, regist_date
FROM Product;  
-- Find the source table data （FROM） Use SELECT Select data retrieval and then use INSERT Insert into the replication table 

- DML ： insert data 
STARTTRANSACTION;
INSERT INTO product VALUES('0001', 'T shirt ', ' clothes ', 1000, 500, '2009-09-20');
INSERT INTO product VALUES('0002', ' Punch ', ' Office Supplies ', 500, 320, '2009-09-11');
INSERT INTO product VALUES('0003', ' motion T T-shirt ', ' clothes ', 4000, 2800, NULL);
INSERT INTO product VALUES('0004', ' kitchen knife ', ' Kitchenware ', 3000, 2800, '2009-09-20');
INSERT INTO product VALUES('0005', ' pressure cooker ', ' Kitchenware ', 6800, 5000, '2009-01-15');
INSERT INTO product VALUES('0006', ' Fork ', ' Kitchenware ', 500, NULL, '2009-09-20');
INSERT INTO product VALUES('0007', ' Clean the board ', ' Kitchenware ', 880, 790, '2008-04-28');
INSERT INTO product VALUES('0008', ' Ball pen ', ' Office Supplies ', 100, NULL, '2009-11-11');
COMMIT;

 

use shop;
-- /* Create a ADDRESSBOOK surface */ 
create TABLE Addressbook (
	regist_no INTEGER NOT NULL,
	name  varchar(128) NOT NULL,
    address VARCHAR(256) NOT NULL,
    tel_no CHAR(10),
    mail_address CHAR(20),
    primary key (regist_no)
    );
	--  Add a column to the table   Fixed length string （8）  Non empty constraint  
ALTER TABLE Addressbook add column	postal_code CHAR(8) NOT NULL;
--  Delete the table  
truncate table Addressbook;

   I watched the tutorial from Alibaba cloud Tianchi  , For personal notes only .