本文主要是介绍Addition, deletion, modification and query of MySQL,对大家解决编程问题具有一定的参考价值,需要的程序猿们随着小编来一起学习吧!
The source of this article is 白居不易
Before the specific work, we should first establish a database containing the data table “student”.(http://www.cnblogs.com/heyangblog/p/7624591.html)
![](/upload/202111/21/202111211940456199.png)
'Addition':Add data
1)Add data for all data in the table
Specify all field names in the Insert statement
Example:INSERT INTO student(id,name,grade)
VALUES(1,'zhangshan',98)
![](/upload/202111/21/202111211940458075.png)
The above result is success
The field name is not specified in the Insert statement
If no field name is specified, the order of the added values should be exactly the same as that of the fields in the table.
Example:INSERT INTO student
VALUES (2,'lisi',62);
![](/upload/202111/21/202111211940459962.png)
The above result is success
2)Adds data to the specified field of the table
Add data for the specified field, that is, add values to only some fields, while the values of other fields are the default values when the table is defined.
Example:INSERT INTO student(id,name)
VALUES(3,'wangwu');
![](/upload/202111/21/202111211940461683.png)
The above result is success
It can be seen that the grade field value of the new record is null because it indicates the grade value when adding, and the system will automatically add the default value.
3)Other ways to write Insert statements
Example:INSERT INTO student
SET id=4,name='zhaoliu',grade=72;
![](/upload/202111/21/202111211940463570.png)
The above result is success
4)Add multiple pieces of data at the same time
Example:INSERT INTO student VALUES
(5,‘lilei’,99),
(6,'hanmeimei',87),
(8,'poly',76);
![](/upload/202111/21/202111211940465468.png)
The above result is success
‘deletion’:Delete from ‘table name’ ‘where’ conditional expression
1)delete some data
command:DELETE FROM student
WHERE id=7;
![](/upload/202111/21/202111211940467364.png)
The above result is success
2)delete all data
command:DELETE FROM student
![](/upload/202111/21/202111211940469252.png)
The above result is success
‘modification’:Update data
Before executing the following statements, use the insert statement to insert the following data into the student table:
1)Update some data
command:UPDATE student
SET name=‘caocao’,grade=50
WHERE id=1;
The above result is success
2)Update all data
command:UPDATE student
SET grade=80;
The above result is success
'query':Single table query
Before the following operations, let's create a new data table student2
![](/upload/202111/21/202111211940476659.png)
Then insert the following data into the student2 table:
INSERT INTO student2(name,grade,gender)
VALUES ('songjiang',40,'男'),('wuyong',100,'男'),('qinming',90,'男'),('husanniang',88,'女'),('sunerniang',66,'女'),('wusong',86,'男'),('linchong',92,'男'),('yanqing',90,NULL);
![](/upload/202111/21/202111211940478398.png)
1)Simple query
Query all fields
command:SELECT id,name,grade ,gender
FROM student2;
![](/upload/202111/21/202111211940480302.png)
The above result is success
Query the specified part of the field
command:SELECT name,gender FROM student2;
![](/upload/202111/21/202111211940482206.png)
The above result is success
The amount of tasks is a little large, unfinished to be continued
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