MySQL's _ additions and deletions to check

Additions and deletions (curd) Curd Explanation: representative creation (create), Updates (update), read (Retrieve), and delete queries basic use

• Querying all Columns

SELECT * from table name;Example:SELECT * from Classes;

• Querying a specified column
  Select column 1, column 2,... from table name;
  Example: select Id,name from Classes;
• Fixed-condition Query
  --Query name for all information of the Li Fei Knife
  SELECT * FROM students where name= "small Li Fei Knife";
  
  --Query name for all information of the Li Fei Knife
  SELECT * FROM students where id>3;
  
  
• You can use as to specify an alias for a column or table

Select field [As Alias], field [as Alias] from data table where ...;
Example: select name as name, gender as gender from students;
Order of Fields
Select ID as serial number, gender as gender, name as name from students; increase

format: INSERT [into] tb_name [(Col_name,...)] {VALUES | VALUE} ({expr | DEFAULT},...), (...),...

• Note: The primary key column is autogrow, but requires a placeholder for full column insertion, usually using 0 or default or null to occupy the position, and the actual data will prevail after the insert succeeds
• Full column Insert: The order of values corresponds to the order of the fields in the table

Insert into table name values (...)Example:INSERT into students values (0, ' Guo Jing ', 1, ' Mongolia ', ' 2016-1-2 ');

• Partial column insertion: The order of values corresponds to the given column order

Insert into table name (column 1,...) VALUES (value 1,...)Example:INSERT into students (Name,hometown,birthday) VALUES (' Huang Rong ', ' Peach Island ', ' 2016-3-2 ');

• The above statement can insert a row of data into a table at a time, and you can insert multiple rows of data at once, which can reduce communication with the database
• Full column multiple row inserts: The order of values corresponds to the given column order

Insert into table name values (...), (...) ...;Example:Insert into classes values (0, ' Python1 '), (0, ' python2 '); Insert into table name (column 1,...) VALUES (value 1,...), (value 1,...) ...;Example:INSERT into students (name) values (' Yang Kang '), (' Yang over '), (' Little Dragon Girl '); modify

format: UPDATE tbname SET col1={expr1| DEFAULT} [, Col2={expr2|default}] ... [Where condition judgment]

Update table name set column 1= value 1, column 2= value 2 ... where conditionExample:Update students set gender=0,hometown= ' Beijing ' where id=5; delete

DELETE from Tbname [where condition judgment]

--Physical deletion
--Delete from table name where condition
Delete from students; --all data in the entire data table is deleted
Delete from students where name= "small Li Fei Knife";

--Logical deletion
--Use a field to indicate whether the message is no longer available.
--Add a is_delete field bit type to the students table
ALTER TABLE students add Is_delete bit default 0;
Update students set is_delete=1 where id=6;

MySQL's _ additions and deletions to check