Mysql = = file (table)

Table Description:

A table is equivalent to a file, and a record in a table is equivalent to a row of files, and a record in a table has a corresponding title, called a field of a table, at different points.

For example: Id,name, age is called a field, and the rest, a line of content is called a record.

1. Create a table

Syntax: CREATE TABLE table name (field name 1 type [(width) constraint], field name 2 Type [(width) constraint]);
Example:
CREATE TABLE T1 (ID int,name char (12));
CREATE TABLE T1 (ID int,name char) engine =innodb default CharSet UTF8;
Note: 1. Field names cannot be the same in a single table. 2. Width and constraints are optional, that is, 3. Field names and types are required.

2. View the table

Syntax: 1.show tables;2.show CREATE table T1; View table structure: 1.describe  t1;  2.desc  T1;

3. Modify the table

Syntax: 1. ALTER TABLE T1 modify name char (n);   #修改表中字段的宽度2. ALTER TABLE course charset = UTF8;        #修改表中的类型3. ALTER TABLE T1 modify name char (n) character set UTF8; #修改表中的类型4. ALTER TABLE t1 rename T2;         #重命名表的名字5. ALTER TABLE T1 add age int;   #添加表中的字段6. ALTER TABLE T1 drop age;      #删除表中的字段7. ALTER TABLE t1 modify ID int not  null primary key auto_increment;  #修改为主键和自动增长8. ALTER TABLE t1 modify ID int not  null;   #删除自增约束9. ALTER TABLE T1 drop PRIMARY key;   #删除主键

4. Copying a table

Copy table structure + record (key will not be copied: primary key, foreign key and Index) syntax: 1. CREATE TABLE NEW_T1 select * from T1; Copy table structure only: 1.select * from T1 where 1=2;  #条件为假, no records are found, so the table's records are not copied 2.create table New_t2 select * from T1 where 1=2;  #只复制表的结构

5. Delete a table

Syntax: Drop  table  name; For example: drop table  t1;

　　

Mysql = = file (table)