We will complete the process from table creation to query in the form of statements
custom database
First we need to create a non-system database
。
define a database
create database <命名>
After creating the database, we need to jump the query statement to our self-built database before creating the table. We use the following code to complete this operation
use <命名>
go
Define base table
create a table
create table <命名>{
<列名><数据类型>[列级完整性约束],
<列名><数据类型>[列级完整性约束],
<列名><数据类型>[列级完整性约束],
primary key<列名>
};
The primary key defines the primary key and is placed in the last row of the created table
.
In addition to basic tables, you can also create table-to-table joins
Create a foreign key
foreign key<命名> references(被参照列)
When defining a foreign key, the referencing table and the referenced table can be the same table
Modify the base table
| clause | effect |
|---|---|
| ADD | Add to |
| DROP | delete |
| ALTER | choose |
delete table
drop table <命名>
Add and delete operations on table columns
ALTER table <命名>
add[column]<新增列名><数据类型>[完整性约束]
add <表级完整性约束>
drop[column] <列名>
special definition of list
cascade 和它相关联的所有对象一起删除，例如视图