MySQL basic DML and DDL learning

DML Add data

# Additions and deletions 
USE atguigudb;
CREATE TABLE IF NOT EXISTS emp1(
	id INT,
	e_name VARCHAR(15),
	hire_date DATE,
	salary DOUBLE(10,2)
);
DESC emp1;
SELECT*FROM emp1;
# Add data 
# The way 1： Add data one by one 
#①  Be sure to add... In the order of the declared fields 
INSERT INTO emp1 
VALUES(1,'Tom','2000-12-21',3400);
SELECT*FROM emp1;
#②  Indicate the field to add   Recommended   More flexible 
INSERT INTO emp1(id,hire_date,salary,e_name)
VALUES(2,'1999-09-09',4000,'Jerry');
# If the fields are incomplete, the default is NULL
INSERT INTO emp1(id,salary,e_name)
VALUES(3,4500,'shk');
#③
INSERT INTO emp1(id,e_name,salary)
VALUES(4,'Jim',5000),(5,' Zhang Junjie ',5500);
SELECT*FROM emp1;
# The way 2： Insert the query results into the table 
SELECT*FROM emp1;

INSERT INTO emp1(id,e_name,salary,hire_date)
# Query statement 
SELECT employee_id,last_name,salary,hire_date# The fields to be queried must correspond to the fields added to the table one by one 
FROM employees
WHERE department_id IN(70,60);
SELECT*FROM emp1;
DESC emp1;
DESC employees;
# explain empl The length of the field to add data in the table cannot be less than employees The length of the query field in the table .
# If you add emp1 The field length of the data to be added in the table is less than employees Query fields in the table 
# There is a risk of adding failure 

DML Update delete operation

# Update data ( Modifying data )
#UPDATE...SET...WHERE...
# Batch modification of data can be realized ,
UPDATE emp1
SET hire_date = CURDATE()
WHERE id = 5;
SELECT*FROM emp1;

# Modify multiple fields of a piece of data at the same time 
UPDATE emp1
SET hire_date =  CURDATE(),salary = 6000
WHERE id = 4;
SELECT*FROM emp1;

# Include the characters... In the names in the table a Salary increase 20%
UPDATE emp1
SET salary = salary *1.2
WHERE e_name LIKE '%a%';
SELECT*FROM emp1;

# There may be unsuccessful cases when modifying data （ It may be due to constraints ）
#update employees
#set department_id = 10000
#where employee_id = 102;


# Delete data  delete ... from...where...
DELETE FROM emp1
WHERE id = 1;
SELECT*FROM emp1;
# When deleting data, it may also fail because of constraints 
#delete from department
#here department_id = 50;
# Summary ：DML Operation by default , Data will be submitted automatically after execution 
# If you want to not automatically submit data after execution , You need to use  SET autocmmit = FLASE;


#MySQL8 New features ： Calculated column 
CREATE TABLE test1(
a INT,
b INT,
c INT GENERATED ALWAYS  AS (a + b) VIRTUAL #C The field is the calculated column 
);

INSERT INTO test1(a,b)
VALUES(10,20);
SELECT*FROM test1;

UPDATE test1
SET a = 100;

DML And DDL Comprehensive case

# Super integrated instance 
# Create database test01_library
CREATE DATABASE IF NOT EXISTS test01_library CHARACTER SET 'utf8';
USE test01_library;

# Create table  books  The table structure is as follows 
CREATE TABLE books(
id INT,
NAME VARCHAR(50),
AUTHORS VARCHAR(100),
price FLOAT,
pubdate YEAR,
note VARCHAR(100),
num INT
);
DESC books;
SELECT*FROM books;

# towards books Insert records in the table 
#1） Do not specify field name , Insert the first record 
INSERT INTO books
VALUES(1,'Tal of AAA','Dickes',23,'1995','novel',11);
SELECT*FROM books;
#2） Specify all field names , Insert the second record 
INSERT INTO books(id,NAME,AUTHORS,price,pubdate,note,num)
VALUES(2,'EmmaT','Jane lura',35,'1993','joke',22);
SELECT*FROM books;
#3） Insert multiple records at the same time （ All the remaining records ）
INSERT INTO books(id,NAME,AUTHORS,price,pubdate,note,num)
VALUES
(3,'Story of Jane','Jane Tim',40,'2001','novel',0),
(4,'Lover Day','George Byron',20,'2005','novel',30),
(5,'Old land','Honore Blade',30,'2010','law',0),
(6,'The Battle','Upton Sara',30,'1999','medicine',40),
(7,'Rose Hood','Richard haggard',28,'2008','cartoon',28);

# Fixed query table statement 
SELECT*FROM books;

# Type the novel (novel) The prices of all the books have increased 5
UPDATE books 
SET price = price + 5
WHERE note = 'novel';

# Title The Book EmmaT Change the price of your book to 40, And change the description to drama.
UPDATE books
SET price = 40,note = 'drama'
WHERE NAME = 'EmmaT';

# Delete repository as 0 The record of 
DELETE FROM books 
WHERE num = 0;

# Included in the title of the statistical book a A Book of letters 
SELECT NAME
FROM books
WHERE NAME LIKE '%a%';

# Included in the title of the statistical book a The number of alphabetic books and the total stock 
SELECT COUNT(*),SUM(num)
FROM books
WHERE NAME LIKE '%a%';

# find "novel" Type of book , In descending order of price 
SELECT NAME,note
FROM books
WHERE note = 'novel'
ORDER BY price DESC;

# Search for book information , Sort by inventory quantity in descending order , If the inventory is the same, follow note Ascending sort 
SELECT *FROM books
ORDER BY num DESC,note ASC;

# according to note Number of classified statistical books 
SELECT note,COUNT(*) " Number "
FROM books
GROUP BY note;

# according to note Inventory quantity of classified statistics , Show that the inventory exceeds 30 Ben's 
SELECT note,SUM(num) " Inventory "
FROM books
GROUP BY note
HAVING SUM(num)>30;

# Search all books , Each page displays five , Show second page 
SELECT*FROM books
LIMIT 5,5;

# according to note Inventory quantity of classified statistics , Displays the most in stock 
# The way 1
SELECT note,MAX(sum_num)
FROM(
SELECT note,SUM(num) sum_num
FROM books
GROUP BY note
) b;
# The way 2
SELECT note,SUM(num) sum_num
FROM books
GROUP BY note
ORDER BY sum_num DESC
LIMIT 0,1;

# Query the title of the book to 10 Number of characters , Not including the space inside 
SELECT NAME
FROM books
WHERE CHAR_LENGTH(REPLACE(NAME,' ','')) >=10;

# Check the title and type of the book , among note The value is novel Show novel ,law Show legal ,medicine Show medicine 
#cartoon Show cartoon ,joke Show jokes 
SELECT NAME " Title ",note,CASE note WHEN 'novel' THEN ' A novel '
				  WHEN 'law' THEN ' law '
				  WHEN 'medicine' THEN ' medicine '
				  WHEN 'cartoon' THEN ' cartoon '
				  WHEN 'joke' THEN ' joke '
				  ELSE ' other '
				  END " type "
FROM books

# Check the title and inventory , among num Value exceeds 30 Ben's , Show unsalable , Greater than 0 And below 10 Of ,
# Show best sellers , by 0 The display of is out of stock 
SELECT NAME " Title ",num AS " stock ",CASE WHEN num>30 THEN ' Unsalable '
				       WHEN num>0 AND num<10 THEN ' Sell well '
				       WHEN num=0 THEN ' No goods '
				       ELSE ' normal '
				       END " Display state "
FROM books;
# Count each Note Total inventory and total amount 
SELECT IFNULL(note,' Total inventory ') AS note,SUM(num)
FROM books
GROUP BY note WITH ROLLUP;

# Count each note The number of , And total 
SELECT IFNULL(note,' Total inventory ') AS note,COUNT(*)
FROM books
GROUP BY note WITH ROLLUP;

# Count the top three books in stock 
SELECT*FROM books
ORDER BY num DESC
LIMIT 0,3;

# Find the first book published 
SELECT *FROM books
ORDER BY pubdate ASC 
LIMIT 0,1;

# find novel The most expensive book in 
SELECT * FROM books
WHERE note = 'novel'
ORDER BY price DESC
LIMIT 0,1

# Find the book with the most words in the title , No spaces 
SELECT *
FROM books
ORDER BY  CHAR_LENGTH(REPLACE(NAME,' ','')) DESC 
LIMIT 0,1;