Apply運(yùn)算符可以實(shí)現(xiàn)兩個(gè)查詢結(jié)果的全組合結(jié)果，又稱為交叉集合。例如兩個(gè)數(shù)據(jù)組合（A,B）、（A,B），他們的交叉集合為（AA，AB，AA，AB）。
create table StudentList(
id int Identity(1,1) not null,
Name nvarchar(20) not null,
Sex bit not null,
Birthday date not null,
Class nvarchar(2) not null,
Grade nvarchar(2) not null,
regdate date not null,
Primary key (id));
create table ScoreInfo(
id int Identity(1,1) not null primary key,
StudentID int not null,
ClassID int not null,
Score int not null,
TestDate date not null,
regdate date not null);
insert into StudentList(Name, Sex, Birthday, Class, Grade, regdate) values('張三', 1, '1988-05-28', 1, 8, '2010-05-05');
insert into StudentList(Name, Sex, Birthday, Class, Grade, regdate) values('李四', 1, '1985-09-13', 4, 4, '2010-05-05');
insert into StudentList(Name, Sex, Birthday, Class, Grade, regdate) values('王麗', 0, '1987-11-05', 1, 7, '2010-05-05');
insert into ScoreInfo(StudentID, ClassID, Score, TestDate, regdate) values(1, 1, 98, '2010-04-15', '2010-05-01');
insert into ScoreInfo(StudentID, ClassID, Score, TestDate, regdate) values(1, 2, 92, '2010-04-15', '2010-05-01');
insert into ScoreInfo(StudentID, ClassID, Score, TestDate, regdate) values(1, 3, 86, '2010-04-15', '2010-05-01');
insert into ScoreInfo(StudentID, ClassID, Score, TestDate, regdate) values(2, 1, 95, '2010-04-15', '2010-05-01');
insert into ScoreInfo(StudentID, ClassID, Score, TestDate, regdate) values(2, 2, 94, '2010-04-15', '2010-05-01');
insert into ScoreInfo(StudentID, ClassID, Score, TestDate, regdate) values(2, 3, 91, '2010-04-15', '2010-05-01');
insert into ScoreInfo(StudentID, ClassID, Score, TestDate, regdate) values(3, 1, 90, '2010-04-15', '2010-05-01');
insert into ScoreInfo(StudentID, ClassID, Score, TestDate, regdate) values(3, 2, 88, '2010-04-15', '2010-05-01');
insert into ScoreInfo(StudentID, ClassID, Score, TestDate, regdate) values(3, 3, 90, '2010-04-15', '2010-05-01');
Cross Apply把語句兩邊的兩個(gè)Select查詢結(jié)果進(jìn)行交叉配對(duì)，將所有結(jié)果展示出來。Cross Apply查詢確保在查詢兩個(gè)子集數(shù)據(jù)的交集時(shí)，只有有效信息的集合才被列出來。
