Question

我的代码如下如何在TSQL选择

中为每一行的特定范围生成随机日期

    Declare @id int;
    Declare @randomDate;
    Declare crs Cursor For
    Select id from myTable 
    open crs 
    fetch next from crs into @id
    while @@FETCH_STATUS=0
    begin
    SET @randomDate=''
    --Generate randomdate @randomDate
    update myTable set dateModified=@randomDate where id=@id;
    fetch next from crs into @id
    end
    close crs
    deallocate crs

Answer 1

按照以下answer，

Update myTable
SET
 dateModified = DATEADD(day, (ABS(CHECKSUM(NEWID())) % 65530), 0)

您无需任何游标即可完成此操作。对于像这样的简单操作，Cursors are bad。

Answer 2

您可以使用CTE生成有效日期并随机选择其中一个：

class PersonalDetailViewSet(viewsets.ModelViewSet):
    queryset = PersonalDetail.objects.all()
    serializer_class = PersonalDetailSerializer

    def get_queryset(self):
        return PersonalDetail.objects.filter(Q(user_id=self.request.user))

    def perform_create(self, serializer):
        serializer.save(user_id=self.request.user)

    # Not delete icon, id, preview_title

Answer 3

这将提供特定开始日期和结束日期之间的随机日期。我出于性能原因引入了@gap变量，它从主查询中删除了DATEDIFF函数的成本。

DECLARE @start DATETIME = '20170101'
DECLARE @end DATETIME = '20170201'
DECLARE @gap INT = DATEDIFF(DD,@start,@end)

UPDATE mytable SET dateModified = DATEADD(DD,@gap*RAND(),@start)

如何在TSQL选择中的每一行的特定范围内生成随机日期？

3 个答案: