T-sql:不明白为什么IF子句永远不会被调用

I have a table like this:

我有一张这样的桌子:

    CREATE TABLE [dbo].[Scores](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [Score] [float] NULL,
 CONSTRAINT [PK_Scores] PRIMARY KEY CLUSTERED 
(
    [Id] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]
    CR