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我试图弄清楚如何在影响两个表的 SQL 中进行复杂的更新。

我的 2 张桌子看起来像：

  t1: key, val_1 (with key as the primary key)
  t2: t1_key, user_id, val_2 (with t1_key and user_id as the primary key)

我需要弄清楚的是如何进行更新，给定一个 user_id“u”和一个键“k”：

  if  (["u"+"k"] does not exist at all in t2) {
    update t1.val = t1.val+1 where key="k";
    insert ("u","k",1) into t2;
  } else if ( ["u"+"k"] exists in t2 and val_2 < 1 ) {
    update t1.val = t1.val+1 where key="k";
    update t2.val2 = t2.val2+1 where t1_key="k" AND user_id="u";
  }

有任何想法吗？

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1 回答 1

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好吧，您的伪代码看起来与查询完全一样。我在 SQL Fiddle 上为您输入了它： http ://sqlfiddle.com/#!3/19597d/11

declare @k int = 3
declare @user_id int = 1

if not exists (select * from t2
               where user_id = @user_id
               and t1_k = @k) begin
  update t1 set val = val + 1 where k = @k
  insert t2 values (@k, @user_id, 1) 
end else if
  exists ( select * from t2 
          where user_id = @user_id
          and t1_k = @k
          and val < 1) begin
  update t1 set val = val + 1 where k = @k
  update t2 set val = val + 1 
    where t1_k = @k 
    and user_id = @user_id
end

select * from t1;
select * from t2;

但是，当您执行此操作时，您将需要事务。（小提琴似乎不喜欢那样。）

不确定您是否意味着在某些情况下不做任何事情，但您的代码没有最后的 else 子句。

于 2013-07-22T18:36:59.283 回答