Question

假设我正在处理10张图书证，每张卡都有客户价值（例如会员编号，会员姓名......），我需要更新每张卡的价值。

如果我想从数据库中抓取所有十个但只想一次更新一行，是否有替代游标？我知道while循环可能有效但是每次循环时我怎么能抓住一行直到我完成所有10张卡？

Answer 1

不需要使用游标。我大部分时间都在使用它：

declare @uid int -- this is the type unique index on the table you're updating

-- Copy out the unique ids of the rows you want to update to a temporary table
select uid into #temp from customers -- you can use a where condition here

-- Loop through the rows of the temp table
while exists (select 1 from #temp)
begin
  set rowcount 1
  select @uid = uid from #temp -- pull one uid from the temp table
  set rowcount 0
  delete from #temp where uid = @uid -- delete that uid from the temp table

  -- Do something with the uid you have
  update customers set name = 'Joe Shmoe' where uid = @uid

end

Answer 2

可以使用特定列上的聚簇索引在表上循环。因为聚簇索引按排序顺序排列行，所以它可以像循环的索引变量一样使用。

declare @uid int
select @uid = 0 -- assume the uids in table are > 0
declare @rowsaf int
select @rowsaf = 1

while @rowsaf > 1
begin
    set rowcount 1
    select @uid = uid from customers where uid > @uid
    select @rowsaf = @@rowcount

    -- update the row using @uid
end

set rowcount 0

Here is the article详细解释了这一点。

SYBASE中游标的替代方案？

2 个答案: