SQL 如何计算 Oracle 中的唯一行数
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How to count unique rows in Oracle
提问by mck
I have an oracle database table with a lot of columns. I'd like to count the number of fully unique rows. The only thing I could find is:
我有一个包含很多列的 oracle 数据库表。我想计算完全唯一的行数。我唯一能找到的是：
SELECT COUNT(DISTINCT col_name) FROM table;
This however would require me listing all the columns and I haven't been able to come up with syntax that will do that for me. I'm guessing the reason for that is that this query would be very low performance? Is there a recommended way of doing this?
但是，这需要我列出所有列，而我无法想出可以为我做到这一点的语法。我猜这是因为这个查询的性能会非常低？有推荐的方法吗？
回答by okaram
How about
怎么样
SELECT COUNT(*)
FROM (SELECT DISTINCT * FROM Table)
回答by DLLB
It depends on what you are trying to accomplish. To get a count of the distinct rows by specific column, so that you know what data exists, and how many of that distinct data there are:
这取决于您要实现的目标。要按特定列获取不同行的计数，以便您知道存在哪些数据，以及有多少不同数据：
SELECT DISTINCT
A_CODE, COUNT(*)
FROM MY_ARCHV
GROUP BY A_CODE
--This informs me there are 93 unique codes, and how many of each of those codes there are.
--这告诉我有 93 个唯一代码，以及每个代码有多少。
Another method
另一种方法
--How to count how many of a type value exists in an oracle table:select A_CDE, --the value you need to countcount(*) as numInstances--how many of each valuefrom A_ARCH-- the table where it residesgroup by A_CDE-- sorting method
--如何统计一个oracle表中某个类型值有多少个：select A_CDE,--需要统计count(*) as numInstances的值from A_ARCH--每个值有多少个--所在表group by A_CDE--排序方法
Either way, you get something that looks like this:
无论哪种方式，您都会得到如下所示的内容：
A_CODE Count(*)
1603 32
1600 2
1605 14
回答by T I
I think you want a count of all distinct rows from a table like this
我想你想从这样的表中计算所有不同的行
select count(1) as c
from (
select distinct *
from tbl
) distinct_tbl;
回答by Nerav
SELECT DISTINCT col_name, count(*) FROM table_namegroup by col_name
SELECT DISTINCT col_name, count(*) FROM table_namegroup by col_name
