MySQL syntax (basic)

MySQL grammar

1. Download and install MySQL

2. Log in to the database

   mysql -uroot -p # Use root The user login mysql The server

3. Display all databases

   show databases;

4. Using a database

   use Database name ;

5. Query all data tables in the database

   show tables;

6. View the column information in the data table
   desc Data sheet ;

   mysql> desc person;
   +-------+-------------+------+-----+---------+----------------+
   | Field | Type        | Null | Key | Default | Extra          |
   +-------+-------------+------+-----+---------+----------------+
   | id    | int         | NO   | PRI | NULL    | auto_increment |
   | name  | varchar(10) | NO   |     | NULL    |                |
   +-------+-------------+------+-----+---------+----------------+

7. Create database

   create database Database name ;

8. Delete database
   drop database Database name ;

9. Create data table
   create table Data table name ( Field name , Field type );

   # auto_increment Defined as self increasing , Generally used for primary key , The value will automatically +1
   # primary key Used to define the primary key 
   # default charset  Set the encoding format 
   create table test(id int(10) not null auto_increment,
   name varchar(10) not null,
   age int(10) not null,
   primary key(id)) default charset=utf8;
   

10. Delete data table
    drop table Data table name ;

11. insert data
    insert into Data table name (key1, key2, key3...) values (value1, value2, value3...);

    insert into test(name, age) values (" Zhang San ", 18);

12. Query data
    select * from Data table name ; # Query all contents in the data table
    select Column  from database where Conditions limit N; # Query the contents of the specified conditions in the data table （ front N Data ）

    #  Inquire about test Everything in 
    select * from test;
    
    #  Inquire about test in id=1 Of name
    select name from test where id=1;
    
    #  Inquire about test in age=33 Before 4 individual name
    select name from test where age=33 limit 4;

13. Update data
    update Data table name set column1=value1, column2=value2..where Conditions ;

    #  to update test In the table id=1 when ,name and age Value 
    update test set name=" Li Si ", age=28 where id=1;

14. Delete data
    delete from Data table name where Conditions ;

    #  Delete test Everything in the table ,test The watch still exists , Content delete 
    delete from test;
    
    #  Delete test In the table name=" Li Si " The line of 
    delete from test where name=" Li Si "

15. like usage
    select column from Data sheet where column like "%";

    #  Inquire about test In the table x At the beginning name
    select name from test where name like "x%";
    
    #  Inquire about test In the table d At the end of the name
    select name from test where name like "%d";

16. union usage
    Connect more than two select The results of a statement are combined into a set of results
    select column from table1 union select column from table2;

    #  from person Table and test Table acquisition name Set （ Delete duplicate data ）
    select name from person union select name from test;
    
    #  from person Table and test Table acquisition name Set （ Contains duplicate data ）
    select name from person union all select name from test;

17. alter usage
    add to 、 Delete 、 Modify the columns of the table / constraint

    #  Modify the name of the table 
    alter table person rename to t_person;
    
    #  add to age Column 
    alter table person add age int(10);
    
    #  Delete age Column 
    alter table person drop age;
    
    #  modify age Change the name to column_age
    alter table person change age column_age int(10);
    
    #  modify age Column properties 
    alter table person modify age int(20);