SQL 查询用于查找计数 > 2 的所有单个记录

Question

So I could not find any solution for this. I've seen many ORDER BY and HAVING solutions, which are close, but do not fully deliver what I'm looking for.

I have this:

SELECT *
FROM t1

WHERE t1.placed > '2020-12-01' AND t1.placed < '2020-12-02'

GROUP BY t1.account

HAVING count(t1.account) > 2;

Now this reflects exactly the rows I want to see, but I want them not grouped together. I want the database to give me all the individual rows. Now I tried removing the GROUP BY, but that just doesn't work. So how can I get the same information as above, but shown as individual rows instead of grouped?

Answer 1

Maybe with a sub query (for join) you can solve it easily

select a.*
from table a
inner join (
    select itemID, Count(*)
    from table 
    where placed > '2020-12-01' and placed < '2020-12-02'
    group by itemID
    having Count(*) > 2
) b on a.ItemID = b.itemID

Answer 2

I want the database to give me all the individual rows

This sounds like exists instead of aggreation:

select *
from mytable t
where 
    placed > '2020-12-01' 
    and placed < '2020-12-02'
    and exists (
        select 1 
        from mytable t1 
        where 
            t1.account = t.account 
            and t1.placed > '2020-12-01' 
            and t1.placed < '2020-12-02'
            and t1.placed <> t.placed
    )

This brings entire records whose account appears more than once. An index on (account, placed) might help this query.

You can also use window functions, if your database supports them:

select *
from (
    select t.*, count(*) over(partition by account) as cnt
    from mytable t
    where placed > '2020-12-01' and placed < '2020-12-02'
) t
where cnt > 1

Answer 3

You could use a common table expression to retrieve the required account and then join it again with the accounts table

with accountids(account) as 
  (select account 
   from accounttable 
   where placed > '2020-12-01' and placed < '2020-12-02'
   group by account
   having count(account) > 2)
select a.* 
from accountids ids inner join accounttable a on ids.account = a.account