爲什麼MySQL只更新1字段而不是2？

我試過以下MySQL更新，但它只設置第一個字段c.avg_price_dil而不是第二個字段c.avg_dilution。爲什麼MySQL只更新1字段而不是2？

奇怪的部分是，當我將更新分成兩部分，如下所示，兩個字段都更新。是否存在影響此調用的基於組的函數？

已更新兩個字段 - 僅更新了c.avg_price_dil。

update corp_act as c 
inner join (
    select 
     m.gvkey, m.gvkey_iid, m.date_base, avg(m.price_dil) as avg_price, 
     avg(m.dilution) as avg_dilution 
    from master as m 
    inner join corp_act as c 
    on c.gvkey = m.gvkey AND 
     m.date_base between c.date_base AND 
          LAST_DAY(c.date_base + INTERVAL 11 MONTH) 
    where c.actioncd not in ('N/C','REA','SPN') AND 
     c.actioncd IS NOT NULL 
    group by m.gvkey_iid, c.actioncd) as x 
on 
    x.gvkey = c.gvkey AND 
    x.date_base = c.date_base 
set 
    c.avg_price_dil = if(x.avg_price is null, 0, x.avg_price) AND 
    c.avg_dilution = if(x.avg_dilution is null, 0, x.avg_dilution)

當分成兩個更新，無論工作：

稀釋更新時間： - 正常工作

update corp_act as c 
inner join (
    select 
     m.gvkey, m.gvkey_iid, m.date_base, avg(m.dilution) as avg_dilution 
    from master as m 
    inner join corp_act as c 
    on c.gvkey = m.gvkey AND 
    m.date_base between c.date_base AND 
         LAST_DAY(c.date_base + INTERVAL 11 MONTH) 
    where c.actioncd not in ('N/C','REA','SPN') AND 
     c.actioncd IS NOT NULL 
    group by m.gvkey_iid, c.actioncd) as x 
on 
    x.gvkey = c.gvkey AND 
    x.date_base = c.date_base 
set 
    c.avg_dilution = if(x.avg_dilution is null, 0, x.avg_dilution)

價格更新： - 正常工作

update corp_act as c 
inner join (
    select 
    m.gvkey, m.gvkey_iid, m.date_base, avg(m.price_dil) as avg_price 
    from master as m 
    inner join corp_act as c 
    on c.gvkey = m.gvkey AND 
    m.date_base between c.date_base AND 
         LAST_DAY(c.date_base + INTERVAL 11 MONTH) 
    where c.actioncd not in ('N/C','REA','SPN') AND 
     c.actioncd IS NOT NULL 
    group by m.gvkey_iid, c.actioncd) as x 
on 
    x.gvkey = c.gvkey AND 
    x.date_base = c.date_base 
set 
    c.avg_price_dil = if(x.avg_price is null, 0, x.avg_price)

唯一的d這兩者之間的區別在於，我僅在個別函數中使用了一次函數avg。

任何想法？感謝您的幫助。

來源

2012-06-28 getting-there