/* Cross the apply and Outer real usage is the apply? 
With their inner join and what is the difference between the Left join, can use a simple example shows that, under the thank you very much 
I simulation test under the Cross under the apply and inner join, Outer apply equivalent left associated */
Declare @ Studient table (PersonId varchar (50), PersonName Nvarchar (50)) 
Declare @ Score table (PersonId varchar (50), the Subject Nvarchar (50), Score INT) 
INSERT INTO @ Studient 
SELECT 'A01', 'zhang' union all 
SELECT 'how A02', 'bill' union all 
SELECT 'A05', 'Cathy' 
INSERT INTO @ Score 
SELECT 'A01', 'language', 90 union all 
SELECT 'how A02', 'mathematics', 95 union all 
SELECT 'A03', 'English', 100, 

- CROSS the APPLY of the SELECT * FROM @ Studient A INNER JOIN @ Score ON p. B ersonId=Amy polumbo ersonId 
SELECT * FROM @ Studient A 
CROSS the APPLY 
(SELECT * FROM @ Score B WHERE p. ersonId=Amy polumbo ersonId) C 
/* 
PersonId PersonName PersonId Subject Score 
A01 zhang SAN A01 Chinese 90 
How A02 li si how A02 math 95 
*/

- outer apply equivalent LEFT JOIN 
SELECT * FROM @ Studient A 
The outer apply (SELECT * FROM @ Score B WHERE p. ersonId=Amy polumbo ersonId) C 
/* 
PersonId PersonName PersonId Subject Score 
A01 zhang SAN A01 Chinese 90 
How A02 li si how A02 math 95 
A05 fifty and NULL NULL NULL 
*/