为什么优化会恶化时间以及如何优化查询？

我有一个请求 - 显示所有学生并为所有参加过“文学”课程的人指明成绩，格式为：全名，成绩：

SELECT T1.FIO, T2.ItogovayaOcenka 
FROM ( SELECT DISTINCT ( SELECT Chelovek.FIO 
                         FROM Chelovek 
                         WHERE Chelovek.NumerPassporta = ObuchayushchijsyaNumerPassporta) FIO  
       FROM Ocenka) T1
LEFT JOIN ( SELECT ( SELECT Chelovek.FIO 
                     FROM Chelovek 
                     WHERE Chelovek.NumerPassporta = ObuchayushchijsyaNumerPassporta ) FIO,
                   ItogovayaOcenka 
            FROM Ocenka 
            WHERE ZHurnal_OcenokKursNazvanie='Литература') T2 ON T2.FIO=T1.FIO;

下面是它的物理计划： 现在，不添加索引，我将查询更改为这个（优化查询）：

WITH 
T1 AS ( SELECT DISTINCT ( SELECT Chelovek.FIO 
                          FROM Chelovek 
                          WHERE Chelovek.NumerPassporta = ObuchayushchijsyaNumerPassporta) FIO  
        FROM Ocenka ),
T2 as ( SELECT ( SELECT Chelovek.FIO 
                 FROM Chelovek 
                 WHERE Chelovek.NumerPassporta = ObuchayushchijsyaNumerPassporta) FIO ,
               ItogovayaOcenka 
        FROM Ocenka 
        WHERE ZHurnal_OcenokKursNazvanie='Литература'),
JOINED AS ( SELECT T1.FIO, T2.ItogovayaOcenka 
            FROM T1 
            LEFT JOIN T2 ON T2.FIO=T1.FIO)
SELECT * FROM JOINED; 

但是通过 DATEDIFF 的时间测量指标显示第一个（非优化查询）表现更好。而他的物理位面并没有改变：

优化第一个查询的最佳方法是什么？

Chelovek 表定义如下：

CREATE TABLE Chelovek               
(
NumerPassporta NVARCHAR(200) PRIMARY KEY NOT NULL CHECK (NumerPassporta!=''), 
FIO NVARCHAR(200) UNIQUE NOT NULL CHECK(FIO !='')
);

评价表：

CREATE TABLE Ocenka
(
    Id INT IDENTITY ,--PRIMARY KEY,
    PromezhutochnyeOcenka1 INT NOT NULL CHECK (PromezhutochnyeOcenka1>0),--ПромежуточныеОценки
    PromezhutochnyeOcenka2 INT NOT NULL CHECK (PromezhutochnyeOcenka2>0),--ПромежуточныеОценки
    PromezhutochnyeOcenka3 INT NOT NULL CHECK (PromezhutochnyeOcenka3>0),--ПромежуточныеОценки
    ItogovayaOcenka int NOT NULL CHECK (ItogovayaOcenka>0),
    ZHurnal_OcenokKursNazvanie NVARCHAR(200) NOT NULL CHECK (ZHurnal_OcenokKursNazvanie!=''),
    CONSTRAINT FOREIGN_KursNazvanie FOREIGN KEY (ZHurnal_OcenokKursNazvanie)  REFERENCES ZHurnal_Ocenok(KursNazvanie),
    ObuchayushchijsyaNumerPassporta NVARCHAR(200)  NOT NULL CHECK (ObuchayushchijsyaNumerPassporta!=''),
    --FOREIGN KEY (ObuchayushchijsyaNumerPassporta) REFERENCES Obuchayushchijsya(NumerPassporta)
    CONSTRAINT PRIMARY_KEY_Id PRIMARY KEY(Id)
    
);

这些表填充在一个循环中：

Declare @_NumPass varchar(11)
Set @_NumPass = ''

Declare @_FIO varchar(80)
Set @_FIO = ''

Declare @_PromezhutochnyeOcenka1 int
Set @_PromezhutochnyeOcenka1 = 0

Declare @_PromezhutochnyeOcenka2 int
Set @_PromezhutochnyeOcenka2 = 0

Declare @_PromezhutochnyeOcenka3 int
Set @_PromezhutochnyeOcenka3 = 0

Declare @_ItogovayaOcenka int
Set @_ItogovayaOcenka = 0

Declare @_ZHurnal_OcenokKursNazvanie varchar(80)
Set @_ZHurnal_OcenokKursNazvanie = ''

Declare @RandNumForSubject int
Set @RandNumForSubject=0






Declare @top int 
Set @top = 1000000

Declare @cnt int
Set @cnt = 0

While @cnt < @top
Begin   
    set @_NumPass = convert(varchar(36),newid())
    set @_FIO = convert(varchar(36),newid())
    set @RandNumForSubject = ABS(CHECKSUM(NEWID())) % 7+1
    IF @RandNumForSubject = 1
        BEGIN
            set @_ZHurnal_OcenokKursNazvanie='Matematica'
        END;
    IF @RandNumForSubject = 2
        BEGIN
            set @_ZHurnal_OcenokKursNazvanie='История'
        END;
    IF @RandNumForSubject = 3
        BEGIN
            set @_ZHurnal_OcenokKursNazvanie='Литература'
        END;
    IF @RandNumForSubject = 4
        BEGIN
            set @_ZHurnal_OcenokKursNazvanie='География'
        END;
    IF @RandNumForSubject = 5
        BEGIN
            set @_ZHurnal_OcenokKursNazvanie='Базовая'+'информатика'
        END;
    IF @RandNumForSubject = 6
        BEGIN
            set @_ZHurnal_OcenokKursNazvanie='Биология'
        END;
    IF @RandNumForSubject = 7
        BEGIN
            set @_ZHurnal_OcenokKursNazvanie='Химия'
        END;
    set @_PromezhutochnyeOcenka1 = ABS(CHECKSUM(NEWID())) % 5+1
    set @_PromezhutochnyeOcenka2 = ABS(CHECKSUM(NEWID())) % 5+1
    set @_PromezhutochnyeOcenka3 = ABS(CHECKSUM(NEWID())) % 5+1
    set @_ItogovayaOcenka = (@_PromezhutochnyeOcenka1+@_PromezhutochnyeOcenka2+@_PromezhutochnyeOcenka3)/3


    Insert Into Chelovek values (@_NumPass,@_FIO)

    Insert Into Ocenka values (@_PromezhutochnyeOcenka1,@_PromezhutochnyeOcenka2,@_PromezhutochnyeOcenka3,@_ItogovayaOcenka,@_ZHurnal_OcenokKursNazvanie,@_NumPass)


    Set @cnt = @cnt + 1
End