table of Contents
2. Operation table
1.C (Create): Create
① Grammar:
create table 表名（
Column name 1 data type 1,
Column name 2 data type 2,
......
Column name n data type n
);
Note: There is no need to add a comma (,) in the last column
type of data:
1. int: integer type age int,
2.double: decimal type score double(5,2);
###Note (5, 2) Up to 5 decimal places to retain 2 decimal places
3.date: date, including only year, month and day, yyyy-MM-dd
4.datetime: date, including year, month, day, hour, minute and second yyyy-MM-dd HH:mm:ss
5.timestamp: The time error type includes year, month, day, hour, minute and second yyyy-MM-dd HH:mm:ss
If you do not give this future field assignment, or assignment bit null, the system defaults to the current time, to automatically assign values
6.varchar: string
name varchar(20); The maximum name is 20 characters
zhangsan 8 characters Zhang San 2
2.R (Retrieve): query
Query all the table names in a database show tables;
Query table structure desc table name;
Exercise: ###Create a table:
create table student(
id int,
name varchar(30),
age int,
score double(4,1),
birthday date,
insert_time timestamp
);
3.U(Update): modify
① Modify the table name
alter table table name rename to new table name;
② Modify the character set of the table
alter table table name character set character set name;
③Add a column
alter table table name add column name data type;
④ Modify the column name type
alter table table name change column name new column name new data type;
alter table table name modify column name new data type;
⑤Delete column
alter table table name drop column name;
4. Copy table (insert one)
create table table name like the name of the table being copied;
5.D (Delete): delete
drop table table name;
drop table if exists 表名;
