SQL - 如果声明看似忽略'AND'

Question

我创建了以下存储过程,在创建新员工时将调用该过程.只要员工在Employee表中不存在,插入就应该成功.

为了检查这一点,我决定检查FirstName,LastName和DateOfBirth.如果一行包含所有这些列的3路匹配,则插入失败.

我所看到的是,If语句将我的AND视为OR.如果发生一次匹配,则插入失败.

经过一番搜索,我无法看到我的If结构出了什么问题.任何帮助,将不胜感激.

            Create Procedure CreateEmployee
            (
            @Role_ID Int,
            @FirstName Varchar(50),
            @LastName Varchar(50),
            @DateOfBirth Varchar(50),
            @Active Bit
            )
            As
            Begin

            If Not Exists (Select FirstName From Employee Where FirstName = @FirstName)
                AND Not Exists (Select LastName From Employee Where LastName = @LastName)
                AND Not Exists (Select DateOfBirth From Employee Where DateOfBirth = @DateOfBirth)

                Begin
                Insert Into Employee (Role_ID, FirstName, LastName, DateOfBirth, Active)
                Values (@Role_ID, @FirstName, @LastName, @DateOfBirth, @Active)
                End

            Else
                Begin
                Select 'User already exists!'
                End

            End

Answer 1

为什么你不只是为你的支票运行1个查询？

If Not Exists (Select 1 From Employee 
               Where FirstName = @FirstName 
                     and LastName = @LastName 
                     and DateOfBirth = @DateOfBirth)
    begin
        ...