view的效率问题

遇到一个问题，关于view的效率，请求大家帮忙分析
第一段，
SELECT  a.id ,
        a.change ,
        a.last_quote
FROM    ( SELECT    * ,
                    DATEADD(hh,
                            ( SELECT    CASE WHEN time_zone IS NULL THEN -5
                                             ELSE time_zone
                                        END AS time_zone
                              FROM      users
                              WHERE     id = 15
                            ) + 5, b.time) AS time1 ,
                    DATEADD(hh,
                            ( SELECT    CASE WHEN time_zone IS NULL THEN -5
                                             ELSE time_zone
                                        END AS time_zone
                              FROM      users
                              WHERE     id = 15
                            ) + 5, b.delayed_time) AS delayed_time1 ,
                    ( SELECT TOP 1
                                order_index
                      FROM      USER_SECTION_SETTINGS
                      WHERE     user_id = b.user_id
                                AND theme_id = b.theme_id
                                AND symbol_id = b.id
                                AND order_index IS NOT NULL
                    ) AS order_index
          FROM      V2_SECTION_231 b
          WHERE     id IN ( SELECT  symbol_id
                            FROM    USER_SECTION_SETTINGS
                            WHERE   user_id = 15
                                    AND theme_id = '19' )
                    AND theme_id = '19'
                    AND b.user_id = 15
                    AND b.theme_id = '19'
        ) a
        LEFT JOIN symbols ON a.id = symbols.id
WHERE   is_rt = 1
如果换成 select * 如下显示，速度会快很多，为什么啊 ? 
SELECT  *
FROM    ( SELECT    * ,
                    DATEADD(hh,
                            ( SELECT    CASE WHEN time_zone IS NULL THEN -5
                                             ELSE time_zone
                                        END AS time_zone
                              FROM      users
                              WHERE     id = 15
                            ) + 5, b.time) AS time1 ,
                    DATEADD(hh,
                            ( SELECT    CASE WHEN time_zone IS NULL THEN -5
                                             ELSE time_zone
                                        END AS time_zone
                              FROM      users
                              WHERE     id = 15
                            ) + 5, b.delayed_time) AS delayed_time1 ,
                    ( SELECT TOP 1
                                order_index
                      FROM      USER_SECTION_SETTINGS
                      WHERE     user_id = b.user_id
                                AND theme_id = b.theme_id
                                AND symbol_id = b.id
                                AND order_index IS NOT NULL
                    ) AS order_index
          FROM      V2_SECTION_231 b
          WHERE     id IN ( SELECT  symbol_id
                            FROM    USER_SECTION_SETTINGS
                            WHERE   user_id = 15
                                    AND theme_id = '19' )
                    AND theme_id = '19'
                    AND b.user_id = 15
                    AND b.theme_id = '19'
        ) a
        LEFT JOIN symbols ON a.id = symbols.id
WHERE   is_rt = 1如果换成 select * 如下显示，速度会快很多，为什么啊 ?