SQL CREATE 关键字
CREATE DATABASE
The CREATE DATABASE command is used is to create a new SQL database.
The following SQL creates a database called "testDB"
Example
CREATE DATABASE testDB;
提示: 确保您在创建任何数据库之前拥有管理员权限。创建数据库后，您可以使用以下 SQL 命令在数据库列表中检查它：SHOW DATABASES;
CREATE TABLE
The CREATE TABLE command creates a new table in the database.
The following SQL creates a table called "Persons" that contains five columns: PersonID, LastName, FirstName, Address, and City
Example
CREATE TABLE Persons (
PersonID int,
LastName varchar(255),
FirstName varchar(255),
Address varchar(255),
City varchar(255)
);
CREATE TABLE Using Another Table
The following SQL creates a new table called "TestTables" (which is a copy of two columns of the "Customers" table):
Example
CREATE TABLE TestTable AS
SELECT customername, contactname
FROM customers;
CREATE INDEX
The CREATE INDEX command is used to create indexes in tables (allows duplicate values).
Indexes are used to retrieve data from the database very fast. The users cannot see the indexes, they are just used to speed up searches/queries.
The following SQL creates an index named "idx_lastname" on the "LastName" column in the "Persons" table
CREATE INDEX idx_lastname
ON Persons (LastName);If you want to create an index on a combination of columns, you can list the column names within the parentheses, separated by commas
CREATE INDEX idx_pname
ON Persons (LastName, FirstName);注意: 创建索引的语法在不同的数据库中有所不同。因此：检查您的数据库中创建索引的语法。
注意: 更新带索引的表比更新不带索引的表需要更多时间（因为索引也需要更新）。因此，只对经常搜索的列创建索引。
CREATE UNIQUE INDEX
The CREATE UNIQUE INDEX command creates a unique index on a table (no duplicate values allowed)
The following SQL creates an index named "uidx_pid" on the "PersonID" column in the "Persons" table
CREATE UNIQUE INDEX uidx_pid
ON Persons (PersonID);CREATE VIEW
The CREATE VIEW command creates a view.
A view is a virtual table based on the result set of an SQL statement.
The following SQL creates a view that selects all customers from Brazil
Example
CREATE VIEW [Brazil Customers] AS
SELECT CustomerName, ContactName
FROM Customers
WHERE Country = "Brazil";
CREATE OR REPLACE VIEW
The CREATE OR REPLACE VIEW command updates a view.
The following SQL adds the "City" column to the "Brazil Customers" view
Example
CREATE OR REPLACE VIEW [Brazil Customers] AS
SELECT CustomerName, ContactName, City
FROM Customers
WHERE Country = "Brazil";
Query The View
We can query the view above as follows
Example
SELECT * FROM [Brazil Customers];
CREATE PROCEDURE
The CREATE PROCEDURE command is used to create a stored procedure.
A stored procedure is a prepared SQL code that you can save, so the code can be reused over and over again.
The following SQL creates a stored procedure named "SelectAllCustomers" that selects all records from the "Customers" table
Example
CREATE PROCEDURE SelectAllCustomers
AS
SELECT * FROM Customers
GO;
Execute the stored procedure above as follows
Example
EXEC SelectAllCustomers;
