练习SQL CHECK CONSTRAINT with FUNCTION

Question

我试图从不是服务器的员工创建阻止订单。这是我的diagram该项目。我的代码，我创建运行正常，但我还可以凭谁不是在“服务器”

CREATE FUNCTION dbo.chk_server_position(@employee_ID int) 
RETURNS varchar(50) 
AS 
BEGIN 
    DECLARE @position varchar(50); 
    DECLARE @employeeID int; 
    DECLARE @output varchar(50); 
    SELECT @position = employee.position, @employeeID = orderInfo.employee_ID 
    FROM employee, orderInfo 
    WHERE employee.employee_ID = orderInfo.employee_ID 
    IF (@position = 'server') 
     SET @output = 'true' 
    return @output; 
END; 
GO 

ALTER TABLE orderInfo 
ADD CONSTRAINT chk_position CHECK (dbo.chk_server_position(employee_ID) = 'true') 

显然，我已经改变了代码，这

CREATE FUNCTION dbo.chk_server_position(@employee_ID int) 
RETURNS varchar(50) 
AS 
BEGIN 
    DECLARE @position varchar(50); 
    DECLARE @employeeID int; 
    DECLARE @output varchar(50); 
    SET @employeeID = (SELECT employee_ID FROM orderInfo) 
    SET @position = (SELECT position FROM employee, orderInfo 
        WHERE employee.employee_ID = orderInfo.employee_ID AND employee.employee_ID = @employee_ID) 

    IF (@position = 'server') 
     SET @output = 'true' 
    return @output; 
END; 
GO 

员工插入和现在，我得到错误信息 子查询返回多个值。当子查询遵循=，！=，<，< =，>，> =或当子查询用作表达式时，这是不允许的。 运行

ALTER TABLE orderInfo 
ADD CONSTRAINT chk_position CHECK (dbo.chk_server_position(employee_ID) = 'true') 

哪种方法更接近导致什么时候？

Answer 1

没关系，我解决了这个问题TRIGGER

CREATE TRIGGER check_employee_position 
ON orderInfo 
INSTEAD OF INSERT 
AS 
BEGIN 
    DECLARE @position VARCHAR(50); 
    DECLARE @employeeID INT = (SELECT i.employee_ID FROM inserted i); 
    SET @position = (SELECT position FROM employee WHERE employee_ID = @employeeID) 
    IF (@position = 'server') 
     INSERT INTO orderInfo(employee_ID, tableNo) VALUES (@employeeID, (SELECT i.tableNo FROM inserted i)) 
END 

Answer 2

由于您的“上次选择”员工不是服务器，您总是插入记录，您错过了给定员工的过滤。

您在USP的Where子句中没有使用@employee_ID参数。 修改您的where子句，如： WHERE employee.employee_ID = orderInfo.employee_ID and employee.employee_ID = @employee_ID

更新： 为什么你需要选择@EmployeeID在USP？你可以写，就像下面：

CREATE FUNCTION dbo.chk_server_position(@employee_ID int) 
RETURNS varchar(50) 
AS 
BEGIN 
    DECLARE @position varchar(50); 
    DECLARE @output varchar(50) = 'false'; 

    SELECT @position = position FROM employee 
    inner join orderInfo ON employee.employee_ID = orderInfo.employee_ID 
    WHERE employee.employee_ID = @employee_ID) 

    IF (@position = 'server') 
     SET @output = 'true' 
    return @output; 

END; 
GO