插入時選擇？

Question

我不確定是否有可能，但我正在嘗試做一個插入，同時選擇一個值做+1。我這樣做的原因是因爲我的列是自動增量，但值都遍佈各地。

這裏就是我有這麼遠，它不會讓我做插件：

insert into channels set chanid=(select chanid from channels where parent=2 
order by chanid desc limit 1)+1 

Answer 1

嘗試在子查詢中使用別名。它爲我做了詭計。

insert into channels 
set chanid=(
    select c.chanid 
    from channels as c 
    where c.parent=2 
    order by c.chanid desc 
    limit 1 
)+1 

參考：http://bugs.mysql.com/bug.php?id=6980

Answer 2

insert into channels(chanid) 
select chanid+1 from channels where parent=2 
order by chanid desc limit 1 

Answer 3

如果我理解正確你的問題試試這個！

insert into channels set chanid=(select chanid+1 from channels where parent=2 order by chanid desc limit 1) 

Answer 4

要重置auto-increment值，你可以嘗試

SET @var_count = 0; 

UPDATE channels 
SET chanid = (@var_count := @var_count + 1); 

或

下降auto-increment柱，用PRIMARY KEY它重新創建它。