[mysql_11] addition, deletion and modification of data processing

1. insert data

With atguigudb.departments Table as an example

1.1 The way 1：VALUES The way to add

Using this syntax, only one piece of data can be inserted into the table at a time . situation 1： Inserts data in the default order for all fields of the table

INSERT INTO  Table name  VALUES (value1,value2,....);
 Copy code 

The above insertion method needs to specify values for each field of the table , And the order of values must be the same as that of fields in the data table . give an example ：

INSERT INTO departments VALUES (70, 'Pub', 100, 1700);

INSERT INTO departments VALUES(100, 'Finance', NULL, NULL);
 Copy code 

situation 2： Insert data for the specified fields of the table

INSERT INTO  Table name (column1 [, column2, …, columnn]) VALUES (value1 [,value2, …, valuen]);
 Copy code 

Insert data for the specified fields of the table , Is in the INSERT Statement inserts values into only some fields , The values of other fields are the default values when the table is defined . stay INSERT Column names are arbitrarily listed in the clause , But once listed ,VALUES To insert value1,....valuen Need and column1,...columnn The columns correspond one by one . If the type is different , Will not be able to insert , also MySQL There will be mistakes . give an example ：

INSERT INTO departments(department_id, department_name) VALUES (80, 'IT');
 Copy code 

situation 3： Insert multiple records at the same time INSERT Statement can insert multiple records into the data table at the same time , Specify multiple value lists when inserting , Each value list is separated by commas , The basic syntax is as follows ：

INSERT INTO table_name 
VALUES 
(value1 [,value2, …, valuen]),
(value1 [,value2, …, valuen]),
……
(value1 [,value2, …, valuen]);
 Copy code 

perhaps

INSERT INTO table_name(column1 [, column2, …, columnn]) 
VALUES 
(value1 [,value2, …, valuen]),
(value1 [,value2, …, valuen]),
……
(value1 [,value2, …, valuen]);
 Copy code 

give an example ：

mysql> INSERT INTO emp(emp_id,emp_name)
    -> VALUES (1001,'shkstart'),
    -> (1002,'atguigu'),
    -> (1003,'Tom');
Query OK, 3 rows affected (0.00 sec)
Records: 3  Duplicates: 0  Warnings: 0
 Copy code 

Use INSERT When inserting multiple records at the same time ,MySQL It will return some additional information that is not available when performing single line insertion , The meaning of this information is as follows ：

• Records： Indicates the number of records inserted .
• Duplicates： Indicates the records that were ignored during insertion , The reason may be that these records contain duplicate primary key values .
• Warnings： Data values indicating a problem , For example, data type conversion occurs .

A that inserts multiple rows of records at the same time INSERT Statement is equivalent to multiple single line inserts INSERT sentence , But multi line INSERT Statement during processing More efficient . because MySQL Execute a single article INSERT Statement inserts more rows of data than using multiple INSERT Fast sentence , Therefore, when inserting multiple records, it is best to choose to use a single record INSERT Insert... In the form of a statement .

Summary ：

• VALUES Or you could write it as VALUE , however VALUES It's standard writing .
• Character and date data should be enclosed in single quotes .

1.2 The way 2： Insert the query results into the table

INSERT Can also be SELECT Insert the result of the statement query into the table , At this time, it is not necessary to input the values of each record one by one , Just use one INSERT Statement and a line SELECT Statements can quickly insert multiple rows from one or more tables into a table . The basic syntax is as follows ：

INSERT INTO  Target table name 
(tar_column1 [, tar_column2, …, tar_columnn])
SELECT
(src_column1 [, src_column2, …, src_columnn])
FROM  Source table name 
[WHERE condition]
 Copy code 

To summarize the rules of this insertion ：

• stay INSERT Add a subquery to the statement .
• There's no need to write VALUES Clause .
• The list of values in the subquery should be the same as INSERT The column name in Clause corresponds to .

give an example ：

--  All columns 
INSERT INTO emp2 
SELECT * 
FROM employees
WHERE department_id = 90;

--  Specify column insertion 
INSERT INTO sales_reps(id, name, salary, commission_pct)
SELECT employee_id, last_name, salary, commission_pct
FROM   employees
WHERE  job_id LIKE '%REP%';
 Copy code 

2. Update data

• Use UPDATE Statement update data . The grammar is as follows ：

UPDATE table_name
SET column1=value1, column2=value2, … , column=valuen
[WHERE condition]
 Copy code 

• You can update more than one piece of data at a time .
• If you need to roll back data , It needs to be guaranteed in DML front , Set it up ：SET AUTOCOMMIT = FALSE;
• Use WHERE Clause specifies the data to be updated .

UPDATE employees
SET    department_id = 70
WHERE  employee_id = 113;
 Copy code 

• If omitted WHERE Clause , Then all data in the table will be updated .

UPDATE  copy_emp
SET  department_id = 110;
 Copy code 

• Update data integrity error （ Foreign key constraint ）

3. Delete data

• Use DELETE Statement to delete data from a table

DELETE FROM table_name [WHERE <condition>];

-- table_name Specify the table to delete ;
-- “[WHERE ]” Is an optional parameter , Specify deletion criteria , without WHERE Clause ,DELETE Statement will delete all records in the table .
 Copy code 

• Use WHERE Clause deletes the specified record .

DELETE FROM departments WHERE department_name = 'Finance';
 Copy code 

• If omitted WHERE Clause , All data in the table will be deleted
• Data integrity error in delete （ Foreign key constraints ）

4. MySQL8 New characteristics ： Calculated column

What is a calculated column ？ Simply put, the value of a column is calculated from other columns . for example ,a The column value is 1、b The column value is 2,c Columns do not need to be inserted manually , Definition a+b As the result of the c Value , that c Is the calculation column , It is calculated from other columns . stay MySQL 8.0 in ,CREATE TABLE and ALTER TABLE Both support adding calculation Columns . Let's say CREATE TABLE For example . give an example ： Define data table tb1, Then define the fields id、 Field a、 Field b And field c, Which field c Is a calculated column , Used to calculate a+b Value . First create a test table tb1, The statement is as follows ：

CREATE TABLE tb1(
  id INT,
  a INT,
  b INT,
  c INT GENERATED ALWAYS AS (a + b) VIRTUAL
);
 Copy code 

Insert demo data , The statement is as follows ：

INSERT INTO tb1(a,b) VALUES (100,200);
 Copy code 

Query data table tb1 Data in , give the result as follows ：

mysql> SELECT * FROM tb1;
+------+------+------+------+
| id   | a    | b    | c    |
+------+------+------+------+
| NULL |  100 |  200 |  300 |
+------+------+------+------+
1 row in set (0.00 sec)
 Copy code 

Update the data in the data , The statement is as follows ：

mysql> UPDATE tb1 SET a = 500;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 1  Changed: 0  Warnings: 0
 Copy code 

5. Comprehensive case

1、 Create database test01_library 2、 Create table books, The table structure is as follows ： 3、 towards books Insert records in the table

1） Do not specify field name , Insert the first record

2） Specify all field names , Insert second record

3） Insert multiple records at the same time （ All the remaining records ）

4） Type the novel (novel) The prices of all the books have increased 5.

5） Name as EmmaT Change the price of your book to 40, And change the description to drama.

6） Delete inventory as 0 The record of .

7） Included in the title of the statistical book a A Book of letters

8） Included in the title of the statistical book a The number of alphabetic books and the total stock

9） find “novel” Type of book , In descending order of price

10） Search for book information , In descending order of inventory , If the inventory is the same, follow note Ascending order

11） according to note Number of classified statistical books

12） according to note Inventory of classified statistics , Show that the inventory exceeds 30 Ben's

13） Search all books , Each page shows 5 Ben , Show second page

14） according to note Inventory of classified statistics , Displays the most in stock

15） Query the title of the book to 10 A one character book , Not including the space inside

16） 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

17） Check the title of the book 、 stock , among num Value exceeds 30 Ben's , Show unsalable , Greater than 0 And below 10 Of , Show best sellers , by 0 The display needs to be out of stock

18） Count each note The stock of , And total

19） Count each note The number of , And total

20） Count the top three books in stock

21） Find the first book published

22） find novel The most expensive book in

23） Find the book with the most words in the title , No spaces

answer ：

#1、 Create database test01_library
CREATE DATABASE IF NOT EXISTS test01_library CHARACTER SET 'utf8';

# Specify which database to use 
USE test01_library;

#2、 Create table  books
CREATE TABLE books(
    id INT,
    name VARCHAR(50),
    `authors` VARCHAR(100) ,
    price FLOAT,
    pubdate YEAR ,
    note VARCHAR(100),
    num INT
);

#3、 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);

# 2） Specify all field names , Insert second record 
INSERT INTO books (id,name,`authors`,price,pubdate,note,num)
VALUES(2,'EmmaT','Jane lura',35,1993,'Joke',22);

# 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,'Lovey 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);

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

# 5、 Name as 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';

# 6、 Delete inventory as 0 The record of .
DELETE FROM books WHERE num=0;

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

# 8、 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%';

# 9、 find “novel” Type of book , In descending order of price 
SELECT * FROM books WHERE note = 'novel' ORDER BY price DESC;

# 10、 Search for book information , In descending order of inventory , If the inventory is the same, follow note Ascending order 
SELECT * FROM books ORDER BY num DESC,note ASC;

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

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

# 13、 Search all books , Each page shows 5 Ben , Show second page 
SELECT * FROM books LIMIT 5,5;

# 14、 according to note Inventory of classified statistics , Displays the most in stock 
SELECT note,SUM(num) sum_num FROM books GROUP BY note ORDER BY sum_num DESC LIMIT 0,1;

# 15、 Query the title of the book to 10 A one character book , Not including the space inside 
SELECT * FROM books WHERE CHAR_LENGTH(REPLACE(name,' ',''))>=10;

/* 16、 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 AS " 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 '
 END AS " type "
FROM books;
# 17、 Check the title of the book 、 stock , among num Value exceeds 30 Ben's , Show unsalable , Greater than 0 And below 10 Of , Show best sellers , by 0 The display needs to be out of stock 
SELECT name,num,CASE 
  WHEN num>30 THEN ' Unsalable '
  WHEN num>0 AND num<10 THEN ' Sell well '
  WHEN num=0 THEN ' No goods '
  ELSE ' normal '
  END AS " Inventory status "
FROM books;

# 18、 Count each note The stock of , And total 
SELECT IFNULL(note,' Total inventory ') AS note,SUM(num) FROM books GROUP BY note WITH ROLLUP;

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

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

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

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

# 23、 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;
 Copy code