MySQL (ii)

Table operation of the data 1. Create a table

Syntax: CREATE TABLE table_name (column_name column_type);

CREATE TABLE student,    ID int not NULL auto_increment,    name CHAR (+) NOT NULL,--age    INT not NU LL,    register_data DATE,    PRIMARY KEY (ID)    );

Auto_increment said: increased by 1. When the write content is empty, the default is to populate the table with a drop-down. Primary key: Represents a constraint (cannot be duplicated and cannot be empty); Accelerate find NOT null: not empty

2. View the table

Show tables;      --See what tables are DESC student;     --View Student table information show create table student;    -View the information created by table student

3. Delete a table

#drop Table name drop table student;

4. Modify the table

Method:

Add Column: ALTER TABLE table name add column name type Delete column: ALTER TABLE table name drop Column name Modify column:        ALTER TABLE table name modify column name type;  --type ALTER TABLE name change original column name        new column name type;--column name, type   add primary key:        ALTER TABLE table name add primary key (column name); Delete PRIMARY key:        alter TABL e table Name drop primary key;        ALTER TABLE name  modify  column name int, drop primary key;   Add foreign key: ALTER TABLE from TABLE ADD constraint foreign key name (shape: fk_ from Table _ Main Table) foreign key from table (foreign key field) references Main Table (primary key field); Delete foreign key: ALTER TABLE name drop for Eign key FOREIGN Key name   modifies default value: ALTER TABLE TESTALTER_TBL alter I SET default 1000; Delete defaults: ALTER TABLE TESTALTER_TBL alter I DROP D Efault;

1. Add alter TABLE student add sex CHAR (+);    #--> add a column 2. Delete alter TABLE student drop sex;     #--> Delete a column 3. Modify the table name alter tables student RENAME to students;   #--> Rename 4. Modify the column name alter TABLE students change regisiter_date register_date date, #change field name, type can be changed, modify can only change type

　　

MySQL (ii)