Question

我有一个用作事件日志的表，并存储状态为“In”，“Out”或“Rejected”的用户（有时用户根据外部条件被“拒绝”）。

以下是一些示例数据，以便您了解该表的外观：

Table MyTable
PersonID - State       - DateTime
// data sample
156      - 'Out'       - 02-14-2010 13:04:15
156      - 'In'        - 02-21-2010 09:01:13
16       - 'In'        - 02-21-2010 09:05:01
58       - 'Rejected'  - 02-21-2010 11:04:58
156      - 'Out'       - 02-21-2010 11:10:02

这是一些pseduo check restraint代码，概述了我想做的事情：

CHECK(
        CASE
            WHEN (
                [State] = 'In' AND
                (Select TOP 1 State FROM MyTable WHERE PersonID=@PersonID_ToUpdate)!='In' ORDER BY DateTime DESC)
            )
            THEN 'T'
            WHEN (
                [State] = 'Out' AND
                (Select TOP 1 State FROM MyTable WHERE PersonID=@PersonID_ToUpdate)!='Out' ORDER BY DateTime DESC)
            )
            THEN 'T'
            WHEN (
                [State] = 'Rejected' AND
                (Select TOP 1 State FROM MyTable WHERE PersonID=@PersonID_ToUpdate)!='In' ORDER BY DateTime DESC)
            )
            THEN 'T'
            ELSE 'F'
        END = 'T'
)

基本上：

如果某人的上一个州不'In'

IN

如果某个人的上一个州不'Out'，则可以签署 OUT
如果某个人的最后状态不'In'

拒绝

我不知道Check Constraint是否是执行此操作的最佳方式，或者我的数据库设计是否允许此级别的约束;如果我不在意，请告诉我（并建议更合适的方法来存储数据和/或确保数据完整性）

注意：我正在使用SQL-Server 2008

Answer 1

这是一个示例触发器。它假设你一次只插入一行（这可能是这里的情况），我没有打扰索引等。

我在状态为'Out'时添加了一个条款，因此它忽略了'Rejected'状态 - 这是为了防止多个Out。它非常基本，但你明白了。

if object_id('dbo.MyTable') is not null     
    drop table dbo.MyTable;

create table dbo.MyTable (
    PersonID int not null,
    [State] varchar(20) not null,
    [DateTime] datetime not null default(getdate())
    ); 

if object_id('dbo.ins_MyTable_status_validation') is not null drop trigger dbo.ins_MyTable_status_validation;
go
create trigger dbo.ins_MyTable_status_validation
    on dbo.MyTable
    instead of insert
as 
begin
    set nocount on;

    -- assuming you're only inserting 1 row at a time (which makes sense for an event log)
    if (select count(*) from inserted) > 1 begin
        print 'Multiple rows inserted - raise some kind of error and die'
        return
    end

    declare @personid_toupdate int,
            @state varchar(20);

    select  @personid_toupdate = personid,
            @state = [state]
    from    inserted;

    if case
        when (
            @state = 'In' and
            isnull((select top 1 [State] from dbo.MyTable where personid = @personid_toupdate order by [datetime] desc), 'Blah') != 'In'
            )
            then 'T'
        when (
            @state = 'Out' and
            isnull((select top 1 [State] from dbo.MyTable where personid = @personid_toupdate and [State] != 'Rejected' order by [datetime] desc), 'Blah') != 'Out' 
            )
            then 'T'
        when (
            @state = 'Rejected' and
            isnull((select top 1 [State] from dbo.MyTable where personid = @personid_toupdate order by [datetime] desc), 'Blah') != 'In'
            )
            then 'T'
            else 'F'
        end = 'T'
    begin
        -- data is valid, perform the insert
        insert  dbo.MyTable (PersonID, [State]) 
        select  PersonID, [State]
        from    inserted; 
    end
    else
    begin
        -- data is invalid, return an error (something a little more informative than this perhaps)
        raiserror('bad data...', 16, 1)
    end
end
go

-- test various combinations to verify constraints
insert  dbo.MyTable (PersonID, [State]) values (1, 'In')
insert  dbo.MyTable (PersonID, [State]) values (1, 'Out')
insert  dbo.MyTable (PersonID, [State]) values (1, 'Rejected')

select * from dbo.MyTable

Answer 2

你必须使用触发器。

您可以在检查约束中使用udf来隐藏表访问权限。但不要。

SQL Server检查约束并检查签名输入/输出状态

2 个答案: