我正在与sql中的distinct关键字进行斗争。
我只想在列和列中显示唯一（distinct）值的所有行号。所以我试过了：
SELECT distinct id, ROW_NUMBER() OVER (ORDER BY id) AS RowNum
FROM table
where fid = 64
但是下面的代码给出了distinct值：
SELECT distinct id FROM table where fid = 64
但是在使用Row_Number时尝试了它
然后它无法正常工作。
答案 0 :(得分：83)
这可以非常简单地完成，你已经非常接近了
SELECT distinct id, DENSE_RANK() OVER (ORDER BY id) AS RowNum
FROM table
WHERE fid = 64
答案 1 :(得分：43)
使用此：
SELECT *, ROW_NUMBER() OVER (ORDER BY id) AS RowNum FROM
(SELECT DISTINCT id FROM table WHERE fid = 64) Base
并将查询的“输出”作为另一个的“输入”。
使用CTE：
; WITH Base AS (
SELECT DISTINCT id FROM table WHERE fid = 64
)
SELECT *, ROW_NUMBER() OVER (ORDER BY id) AS RowNum FROM Base
两个查询应该是等效的。
技术上你可以
SELECT DISTINCT id, ROW_NUMBER() OVER (PARTITION BY id ORDER BY id) AS RowNum
FROM table
WHERE fid = 64
但如果增加DISTINCT字段的数量，则必须将所有这些字段放在PARTITION BY中，例如
SELECT DISTINCT id, description,
ROW_NUMBER() OVER (PARTITION BY id, description ORDER BY id) AS RowNum
FROM table
WHERE fid = 64
我甚至希望你能理解你在这里违反标准命名约定，id应该是主键，因此根据定义是唯一的，所以DISTINCT对它没用，除非你将查询与某些JOIN s / UNION ALL ...
答案 2 :(得分：20)
This article covers an interesting relationship between ROW_NUMBER() and DENSE_RANK()（RANK()函数未被特别处理）。如果您需要在ROW_NUMBER()语句中生成SELECT DISTINCT，则ROW_NUMBER() will produce distinct values before they are removed by the DISTINCT keyword。例如。这个查询
SELECT DISTINCT
v,
ROW_NUMBER() OVER (ORDER BY v) row_number
FROM t
ORDER BY v, row_number
...可能会产生此结果（DISTINCT无效）：
+---+------------+
| V | ROW_NUMBER |
+---+------------+
| a | 1 |
| a | 2 |
| a | 3 |
| b | 4 |
| c | 5 |
| c | 6 |
| d | 7 |
| e | 8 |
+---+------------+
这个查询：
SELECT DISTINCT
v,
DENSE_RANK() OVER (ORDER BY v) row_number
FROM t
ORDER BY v, row_number
...在这种情况下产生你可能想要的东西：
+---+------------+
| V | ROW_NUMBER |
+---+------------+
| a | 1 |
| b | 2 |
| c | 3 |
| d | 4 |
| e | 5 |
+---+------------+
请注意ORDER BY函数的DENSE_RANK()子句需要SELECT DISTINCT子句中的所有其他列才能正常工作。
使用PostgreSQL / Sybase / SQL标准语法（WINDOW子句）：
SELECT
v,
ROW_NUMBER() OVER (window) row_number,
RANK() OVER (window) rank,
DENSE_RANK() OVER (window) dense_rank
FROM t
WINDOW window AS (ORDER BY v)
ORDER BY v
......你会得到：
+---+------------+------+------------+
| V | ROW_NUMBER | RANK | DENSE_RANK |
+---+------------+------+------------+
| a | 1 | 1 | 1 |
| a | 2 | 1 | 1 |
| a | 3 | 1 | 1 |
| b | 4 | 4 | 2 |
| c | 5 | 5 | 3 |
| c | 6 | 5 | 3 |
| d | 7 | 7 | 4 |
| e | 8 | 8 | 5 |
+---+------------+------+------------+
答案 3 :(得分：3)
使用DISTINCT会在添加字段时导致问题，并且还可能会掩盖选择中的问题。使用GROUP BY作为替代方案：
SELECT id
,ROW_NUMBER() OVER (ORDER BY id) AS RowNum
FROM table
where fid = 64
group by id
然后你可以从你的选择中添加其他有趣的信息：
,count(*) as thecount
或
,max(description) as description
答案 4 :(得分：1)
像
这样的东西;WITH DistinctVals AS (
SELECT distinct id
FROM table
where fid = 64
)
SELECT id,
ROW_NUMBER() OVER (ORDER BY id) AS RowNum
FROM DistinctVals
您也可以尝试
SELECT distinct id, DENSE_RANK() OVER (ORDER BY id) AS RowNum
FROM @mytable
where fid = 64
答案 5 :(得分：0)
试试这个
SELECT distinct id
FROM (SELECT id, ROW_NUMBER() OVER (ORDER BY id) AS RowNum
FROM table
WHERE fid = 64) t
或使用RANK()代替行号并选择记录DISTINCT rank
SELECT id
FROM (SELECT id, ROW_NUMBER() OVER (PARTITION BY id ORDER BY id) AS RowNum
FROM table
WHERE fid = 64) t
WHERE t.RowNum=1
这也会返回不同的ID
答案 6 :(得分：0)
试试这个：
;WITH CTE AS (
SELECT DISTINCT id FROM table WHERE fid = 64
)
SELECT id, ROW_NUMBER() OVER (ORDER BY id) AS RowNum
FROM cte
WHERE fid = 64
答案 7 :(得分：0)
问题太老了，我的回答可能不会增加太多，但这是我的两分钱，使查询变得有用：
;WITH DistinctRecords AS (
SELECT DISTINCT [col1,col2,col3,..]
FROM tableName
where [my condition]
),
serialize AS (
SELECT
ROW_NUMBER() OVER (PARTITION BY [colNameAsNeeded] ORDER BY [colNameNeeded]) AS Sr,*
FROM DistinctRecords
)
SELECT * FROM serialize
使用两个cte的用处在于，您现在可以轻松地在查询中使用序列化记录，并且非常轻松地执行count(*)等。
DistinctRecords将选择所有不同的记录，serialize将序列号应用于不同的记录。病房结束后，您可以将最终的序列化结果用于您的目的，而不会造成混乱。
Partition By