代码之家 › 专栏 › 技术社区 › lock

为什么SQL中没有产品聚合函数?

aggregate sql

lock · 技术社区 · 14 年前

我在找类似的东西 SELECT PRODUCT(table.price) FROM table GROUP BY table.sale 类似于 SUM 作品。

我是否遗漏了文件上的内容,或者真的没有 PRODUCT 功能?

如果是这样,为什么不呢?

注意:我在postgres、mysql和mssql中查找了函数,但没有找到,所以我假设所有的sql都不支持它。

9 回复 | 直到 14 年前

onedaywhen 14 年前

PRODUCT CONCATENATE

log exp SUM

Itzik Ben-Gan's blog

Community CDub 8 年前

SELECT
    GrpID,
    CASE
       WHEN MinVal = 0 THEN 0
       WHEN Neg % 2 = 1 THEN -1 * EXP(ABSMult)
       ELSE EXP(ABSMult)
    END
FROM
    (
    SELECT
       GrpID, 
       --log of +ve row values
       SUM(LOG(ABS(NULLIF(Value, 0)))) AS ABSMult,
       --count of -ve values. Even = +ve result.
       SUM(SIGN(CASE WHEN Value < 0 THEN 1 ELSE 0 END)) AS Neg,
       --anything * zero = zero
       MIN(ABS(Value)) AS MinVal
    FROM
       Mytable
    GROUP BY
       GrpID
    ) foo

SQL Server Query - groupwise multiplication

Lord Peter 14 年前

select exp (sum (ln (table.price))) from table ...

Fenton 14 年前

SELECT
    Exp(Sum(IIf(Abs([Num])=0,0,Log(Abs([Num])))))*IIf(Min(Abs([Num]))=0,0,1)*(1-2*(Sum(IIf([Num]>=0,0,1)) Mod 2)) AS P
FROM
   Table1

http://productfunctionsql.codeplex.com/

David Airapetyan 12 年前

declare @Floats as table (value float)
insert into @Floats values (0.9)
insert into @Floats values (0.9)
insert into @Floats values (0.9)

declare @multiplier float = null

select 
    @multiplier = isnull(@multiplier, '1') * value
from @Floats

select @multiplier

naiem 13 年前

Nicolás Sierra 13 年前

SELECT group_concat(table.price) FROM table GROUP BY table.sale

php.net manual

TomáÅ¡ Záluský 6 年前

with recursive t(c) as (
  select unnest(array[2,5,7,8])
), p(a) as (
  select array_agg(c) from t
  union all
  select p.a[2:]
  from p
  cross join generate_series(1, p.a[1])
)
select count(*) from p where cardinality(a) = 0;

TomáÅ¡ Záluský 6 年前

   with recursive t(c) as (
     select unnest(array[2,5,7,8])
   ), r(c,n) as (
     select t.c, row_number() over () from t
   ), p(c,n) as (
     select c, n from r where n = 1
     union all
     select r.c * p.c, r.n from p join r on p.n + 1 = r.n
   )
   select c from p where n = (select max(n) from p);

   with recursive t(sale,price) as (
     select 'multiplication', 2 union
     select 'multiplication', 5 union
     select 'multiplication', 7 union
     select 'multiplication', 8 union
     select 'trivial', 1 union
     select 'trivial', 8 union
     select 'negatives work', -2 union
     select 'negatives work', -3 union
     select 'negatives work', -5 union
     select 'look ma, zero works too!', 1 union
     select 'look ma, zero works too!', 0 union
     select 'look ma, zero works too!', 2
   ), r(sale,price,n,maxn) as (
     select t.sale, t.price, row_number() over (partition by sale), count(1) over (partition by sale)
     from t
   ), p(sale,price,n,maxn) as (
     select sale, price, n, maxn
     from r where n = 1
     union all
     select p.sale, r.price * p.price, r.n, r.maxn
     from p
     join r on p.sale = r.sale and p.n + 1 = r.n
   )
   select sale, price
   from p
   where n = maxn
   order by sale;

sale,price
"look ma, zero works too!",0
multiplication,560
negatives work,-30
trivial,8