a*****e
发帖数: 2503 | 1 I noticed that they said that some Presentation said that
ClO2 reacts only as oxidant so it will generate less THMs compared with Cl2.
Why? |
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B*****g
发帖数: 34098 | 2 这题其实出的挺好的。
意思就是说把所有导致不是1to1的record都删了，也就是留下那些clo1的值在clo1列只
出现一次而且clo2的值在clo2列也只出现一次。如表中给的例子只有V1，B符合要求。
V12 F中的F和V3 F的F重了
V2 C和V2 D的V2重了
V3 E中的F和V3 F的V3重了
and |
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j****s
发帖数: 881 | 5 多谢上面几位解释，尤其是北京姐姐，把题目的意思讲清楚了。
另一种写法:
select col1, col2 from table
where clo1 not in
(select col1, count(col2) from table
group by clo1
having count(col2)>1
Intersect
select col1, col2 from table
select col2, count(col1) from table
group by clo2
having count(col1)>1)
记下IDs，发包子去了。 |
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a*****a
发帖数: 1038 | 6 Keep in mind, only free chlorine reacts with DBP precursor, such as humic
acid, to produce TTHMs or HAA5s. The chlorine dioxide does not produce
these two DBPs above. However, the chlorine dixoide does produce its unique
byproduct, chlorite, which is in the EPA primary drinking water standard.
In the past 10 years, chlorite was found to be an effective inhibitor for
ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) growth
. It has been used for controlling nitrification in |
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a*****e
发帖数: 2503 | 7 靠，回头自己读了一下，自己当时都写的是啥英语啊。
Cl2. |
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a*****e
发帖数: 2503 | 8 多谢artesia前辈。
unique
growth
distribution |
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m*******e
发帖数: 21667 | 9 找本儿Water Treatment: Principles and Design by MWH看看，里面有详细解释
Cl2. |
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