sql - SQL Server默认创建非聚集索引

Question

是的，它是 this 的重复 。但我只需要澄清this article作者:Pinal Dave，内容如下:

Scenario 4: Primary Key defaults to Clustered Index with other index defaults to Non-clustered index

In this case we will create two indexes on the both the tables but we will not specify the type of the index on the columns. When we check the results we will notice that Primary Key is automatically defaulted to Clustered Index and another column as a Non-clustered index.

-- Case 4 Primary Key and Defaults
USE TempDB
GO
-- Create table
CREATE TABLE TestTable
(ID INT NOT NULL PRIMARY KEY,
Col1 INT NOT NULL UNIQUE)
GO
-- Check Indexes
SELECT OBJECT_NAME(OBJECT_ID) TableObject,
[name] IndexName,
[Type_Desc]
FROM sys.indexes
WHERE OBJECT_NAME(OBJECT_ID) = 'TestTable'
GO
-- Clean up
DROP TABLE TestTable
GO

Answer 1

唯一自动创建的索引:

• 主键上的聚集索引(除非您另外指定 - 如果您将主键定义为非聚集，则将创建非聚集索引)

• 将UNIQUE CONSTRAINT应用于一列(或一组列)时的唯一非聚集索引