Say I have two tables: A and B
Table A
+----+-------+
| id | value |
+----+-------+
| 1 | 20 |
| 2 | 20 |
| 3 | 10 |
| 4 | 0 |
+----+-------+
Table B
+----+-------+
| id | value |
+----+-------+
| 1 | 20 |
| 2 | 10 |
| 3 | 30 |
| 4 | 20 |
| 5 | 20 |
| 6 | 10 |
+----+-------+
If I do SELECT value, COUNT(*) AS occurrence FROM A GROUP BY value, I'll get:
+-------+------------+
| value | occurrence |
+-------+------------+
| 20 | 2 |
| 10 | 1 |
| 0 | 1 |
+-------+------------+
Based on this grouping of table A, I want to delete occurrence records from table B with the same values. In other words, I want to delete from B 2 records with value 20, 1 record with value 10, and 1 record with value 0. (Other conditions include 'do nothing if no record exists' and 'smallest id first', but I think these conditions are pretty trivial compared to the bulk of this question.)
Table B after deleting should be:
+----+-------+
| id | value |
+----+-------+
| 3 | 30 |
| 5 | 20 |
| 6 | 10 |
+----+-------+
From the official TOP documentation, doesn't seems like I can perform some JOIN to use as the TOP expression.
We could use ROW_NUMBER with CTEs here:
WITH cteA AS (
SELECT value, COUNT(*) cnt
FROM A
GROUP BY value
),
cteB AS (
SELECT *, ROW_NUMBER() OVER (PARTITION BY value ORDER BY id) rn
FROM B
)
DELETE
FROM cteB b
INNER JOIN cteA a
ON b.value = a.value
WHERE
b.rn <= a.cnt;
The logic here is that we use ROW_NUMBER to keep track of the order of each value in the B table. Then, we join to bring in the counts of each value in the A table, and we only delete B records for which the row number is strictly less than or equal to the A count.
See the demo link below to verify that the logic be correct. Note that I use a select there, not a delete, but the correct rows are being targeted for deletion.
Demo
I have this table called 'Stack'.
+---------------+-------+-------------+
| Stack_Counter | value | Stack_Depth |
+---------------+-------+-------------+
| 1 | 3 | 1 |
| 2 | 0 | 2 |
| 3 | 0 | 1 |
| 4 | | 0 |
| 5 | 3 | 1 |
| 6 | 3 | 2 |
| 7 | 1 | 3 |
| 8 | 2 | 2 |
| 9 | 4 | 1 |
| 10 | 2 | 2 |
| 11 | 0 | 3 |
| 12 | 0 | 2 |
| 13 | 0 | 1 |
| 14 | 2 | 2 |
| 15 | 2 | 3 |
| 16 | 1 | 4 |
| 17 | 1 | 3 |
| 18 | 2 | 2 |
| 19 | 1 | 3 |
| 20 | 0 | 4 |
+---------------+-------+-------------+
I want to find out the stack array in Stack_Counter '20'.
So the correct answer should be
+---------------+-------+-------------+
| Stack_Counter | value | Stack_Depth |
+---------------+-------+-------------+
| 13 | 0 | 1 |
| 18 | 2 | 2 |
| 19 | 1 | 3 |
| 20 | 0 | 4 |
+---------------+-------+-------------+
Basically , this is to find out consecutive rows in selected Stack_Depth.
Is there any way to acheive it?
... and here's a generic all-SQL solution:
SELECT Stack_Counter, value, Stack_Depth
FROM
(SELECT *, RANK() OVER (
PARTITION BY Stack_Depth
ORDER BY Stack_Counter DESC) rank
FROM stack)
WHERE rank=1 AND Stack_Depth > 0;
An SQL-only solution may be more trouble than it's worth (either because of its complexity or its tediousness), but here is one that works with SQLite:
SELECT * FROM (SELECT * FROM stack WHERE Stack_Depth=1 ORDER BY Stack_Counter DESC LIMIT 1)
UNION ALL
SELECT * FROM (SELECT * FROM stack WHERE Stack_Depth=2 ORDER BY Stack_Counter DESC LIMIT 1)
UNION ALL
SELECT * FROM (SELECT * FROM stack WHERE Stack_Depth=3 ORDER BY Stack_Counter DESC LIMIT 1)
UNION ALL
SELECT * FROM (SELECT * FROM stack WHERE Stack_Depth=4 ORDER BY Stack_Counter DESC LIMIT 1);
The window functions I mentioned in comments proved to be more difficult than I thought... for myself at the time. Peak's answer is an elegant solution using the rank() window function, just what I had originally intended. In the mean time, sqlite also supports recursive CTE (Common Table Expressions; WITH statement):
WITH RECURSIVE
latest (id, level) AS (
VALUES (20, (SELECT Stack_Depth FROM stack WHERE Stack_Counter = 20))
UNION ALL
SELECT (SELECT max(Stack_Counter)
FROM stack
WHERE Stack_Depth = level - 1
AND Stack_Counter <= 20),
level - 1
FROM latest
WHERE level - 1 > 0
)
SELECT stack.*
FROM stack INNER JOIN latest
ON stack.Stack_Counter = latest.id
ORDER BY stack.Stack_Counter
There are three places that I had to insert the desired stack level, but these could all be replaced with a named SQL parameter if you're calling this from a prepared statement in the host language.
And if you're not interested in choosing a particular Stack_Counter value, rather just want the result from the entire table, then replace the VALUES clause with a SELECT like
WITH RECURSIVE
latest (id, level) AS (
SELECT * FROM (SELECT Stack_Counter, Stack_Depth FROM stack ORDER BY Stack_Counter DESC LIMIT 1)
UNION ALL
SELECT (SELECT max(Stack_Counter)
FROM stack
WHERE Stack_Depth = level - 1),
level - 1
FROM latest
WHERE level - 1 > 0
)
SELECT stack.*
FROM stack INNER JOIN latest
ON stack.Stack_Counter = latest.id
ORDER BY stack.Stack_Counter
I'm trying to get a "lineage" or similar, and also information about the first and last links (at least; all would be good), out of a table that has self-referential links between rows that have been "replaced" and rows that have replaced them. The table has a structure along these lines:
CREATE TABLE Thing (
Id INT PRIMARY KEY,
TStamp DATETIME,
Replaces INT NULL,
ReplacedBy INT NULL
);
I'm stuck with this structure. :-) It's sort of doubly-linked (yes, it's a bit silly): Each row has a unique Id, and then a row that has been "replaced" by another will have a non-NULL ReplacedBy giving the Id of the replacement row, and the replacement row will also have a link back to what it replaces in Replaces. So we can use either Replaces or ReplacedBy (or both) if we like.
Here's some sample data:
INSERT INTO Thing
(Id, TStamp, Replaces, ReplacedBy)
VALUES
(1, '2017-01-01', NULL, 11),
(2, '2017-01-02', NULL, 12),
(3, '2017-01-03', NULL, NULL),
(4, '2017-01-04', NULL, NULL),
(11, '2017-01-11', 1, NULL),
(12, '2017-01-12', 2, 22),
(22, '2017-01-22', 12, NULL);
So 1 was replaced by 11, 2 was replaced by 12, and 12 was replaced by 22.
I'd like to get the following information for each chain of links from this table in a reasonable way:
Details of the row that started the chain
Details of the final row in the chain
Details of the links in-between or at least how many links (total) there are in the chain
...filtered by a date range applied to the last row in the chain.
In an ideal universe, I'd get back something like this:
+−−−−−−−−−+−−−−−−−−+−−−−+−−−−−−−+−−−−−−−−−−−−+
| FirstId | LastId | Id | Links | TStamp |
+−−−−−−−−−+−−−−−−−−+−−−−+−−−−−−−+−−−−−−−−−−−−+
| 1 | 11 | 1 | 2 | 2017−01−01 |
| 1 | 11 | 11 | 2 | 2017−01−11 |
| 2 | 22 | 2 | 3 | 2017−01−02 |
| 2 | 22 | 12 | 3 | 2017−01−12 |
| 2 | 22 | 22 | 3 | 2017−01−22 |
+−−−−−−−−−+−−−−−−−−+−−−−+−−−−−−−+−−−−−−−−−−−−+
So far I have this query, which I could post-process to get the above:
WITH Data AS (
SELECT Id, TStamp, Replaces, ReplacedBy, 0 AS Depth
FROM Thing
UNION ALL
SELECT Thing.Id, Thing.TStamp, Thing.Replaces, Thing.ReplacedBy, Depth + 1
FROM Data
JOIN Thing
ON Thing.Replaces = Data.Id
)
SELECT *
FROM Data
WHERE ReplacedBy IS NOT NULL OR Depth > 0
ORDER BY
Id, Depth;
That gives me:
+−−−−+−−−−−−−−−−−−+−−−−−−−−−−+−−−−−−−−−−−−+−−−−−−−+
| Id | TStamp | Replaces | ReplacedBy | Depth |
+−−−−+−−−−−−−−−−−−+−−−−−−−−−−+−−−−−−−−−−−−+−−−−−−−+
| 1 | 2017−01−01 | NULL | 11 | 0 |
| 2 | 2017−01−02 | NULL | 12 | 0 |
| 11 | 2017−01−11 | 1 | NULL | 1 |
| 12 | 2017−01−12 | 2 | 12 | 0 |
| 12 | 2017−01−12 | 2 | 12 | 1 |
| 22 | 2017−01−13 | 12 | NULL | 1 |
| 22 | 2017−01−13 | 12 | NULL | 2 |
+−−−−+−−−−−−−−−−−−+−−−−−−−−−−+−−−−−−−−−−−−+−−−−−−−+
And I could use something like this to figure out (for instance) the final row of each chain:
WITH Data AS (
SELECT Id, Replaces, ReplacedBy, 0 AS Depth
FROM Thing
UNION ALL
SELECT Thing.Id, Thing.Replaces, Thing.ReplacedBy, Depth + 1
FROM Data
JOIN Thing
ON Thing.Replaces = Data.Id
),
MaxData AS (
SELECT Data.Id, Data.Depth
FROM Data
JOIN (
SELECT Id, MAX(Depth) AS MaxDepth
FROM Data
GROUP BY Id
) j ON data.Id = j.Id AND Data.Depth = j.MaxDepth
WHERE Depth > 0
)
SELECT *
FROM MaxData
ORDER BY
Id;
...which gives me:
+−−−−+−−−−−−−+
| Id | Depth |
+−−−−+−−−−−−−+
| 11 | 1 |
| 12 | 1 |
| 22 | 2 |
+−−−−+−−−−−−−+
...but I've lost the starting point and the points along the way.
I have the strong feeling I'm missing something really straight-forward — but clever — that would let me get this largely with the query rather than post-processing, some kind of join with a "min" and "max" query (but not like my one above). What would it be?
The table doesn't have any indexes on Replaces or ReplacedBy, but we could add any needed. The table is only lightly used (roughly 300k rows and probably only a couple of hundred updates/inserts a day).
I'm limited to SQL Server 2008 features.
Inspired by Gordon Linoff's answer and HABO's comment which highlighted something Gordon was doing that was critical, I:
Removed the SQL Server 2012+ FIRST_VALUE function, replacing it with a CROSS JOIN on an "overview" query of the data
Included the Links count in the overview query
Removed the reliance on t in Gordon's WHERE NOT EXISTS (SELECT 1 FROM Thing t2 WHERE t2.ReplacedBy = t.id), which (at last on SQL Server 2008) wasn't bound to anything
Filtered out rows that weren't replaced
Below, I also add the date filtering mentioned in the question
...filtered by a date range applied to the last row in the chain.
...which Gordon didn't cover at all, and changes our approach, but only in terms of the arrow of time.
So, first, without the date criteria, sticking fairly close to Gordon's answer:
WITH Data AS (
SELECT Id AS FirstId, Id, TStamp, Replaces, ReplacedBy, 0 AS Depth
FROM Thing
WHERE Replaces IS NULL AND ReplacedBy IS NOT NULL
UNION ALL
SELECT d.FirstId, t.Id, t.TStamp, t.Replaces, t.ReplacedBy, d.Depth + 1
FROM Data d
JOIN Thing t ON t.Replaces = d.Id
),
Overview AS (
SELECT FirstId, MAX(Id) AS LastId, COUNT(*) AS Links
FROM Data
GROUP BY
FirstId
)
SELECT d.FirstId, o.LastId, d.Id, o.Links, d.Depth, d.TStamp
FROM Data d
CROSS APPLY (
SELECT LastId, Links
FROM Overview
WHERE FirstId = d.FirstId
) o
ORDER BY
d.FirstId, d.Depth
;
The critical parts of that are grabbing the seed Id as FirstId here:
SELECT Id AS FirstId, Id, TStamp, Replaces, ReplacedBy, 0 AS Depth
FROM Thing
WHERE Replaces IS NULL AND ReplacedBy IS NOT NULL
and then propagating it through the results of the recursive join:
SELECT d.FirstId, t.Id, t.TStamp, t.Replaces, t.ReplacedBy, d.Depth + 1
FROM Data d
JOIN Thing t ON t.Replaces = d.Id
Just adding that to my original query gives us most of what I wanted. Then we add a second query to get the LastId for each FirstId (Gordon did it as a FIRST_VALUE over a partition, but I can't do that in SQL Server 2008) and using an overview query also lets me grab the number of links. We cross-apply that on the basis of the FirstId value to get the overall results I wanted.
The query above returns the following for the sample data:
+−−−−−−−−−+−−−−−−−−+−−−−+−−−−−−−+−−−−−−−+−−−−−−−−−−−−+
| FirstId | LastId | Id | Links | Depth | TStamp |
+−−−−−−−−−+−−−−−−−−+−−−−+−−−−−−−+−−−−−−−+−−−−−−−−−−−−+
| 1 | 11 | 1 | 2 | 0 | 2017-01-01 |
| 1 | 11 | 11 | 2 | 1 | 2017-01-11 |
| 2 | 22 | 2 | 3 | 0 | 2017-01-02 |
| 2 | 22 | 12 | 3 | 1 | 2017-01-12 |
| 2 | 22 | 22 | 3 | 2 | 2017-01-13 |
+−−−−−−−−−+−−−−−−−−+−−−−+−−−−−−−+−−−−−−−+−−−−−−−−−−−−+
...e.g., exactly what I wanted, plus Depth if I want (so I know what order the intermediary links were in).
If we wanted to include rows that were never replaced, we'd just change
WHERE Replaces IS NULL AND ReplacedBy IS NOT NULL
to
WHERE Replaces IS NULL
Giving us:
+−−−−−−−−−+−−−−−−−−+−−−−+−−−−−−−+−−−−−−−+−−−−−−−−−−−−+
| FirstId | LastId | Id | Links | Depth | TStamp |
+−−−−−−−−−+−−−−−−−−+−−−−+−−−−−−−+−−−−−−−+−−−−−−−−−−−−+
| 1 | 11 | 1 | 2 | 0 | 2017-01-01 |
| 1 | 11 | 11 | 2 | 1 | 2017-01-11 |
| 2 | 22 | 2 | 3 | 0 | 2017-01-02 |
| 2 | 22 | 12 | 3 | 1 | 2017-01-12 |
| 2 | 22 | 22 | 3 | 2 | 2017-01-13 |
| 3 | 3 | 3 | 1 | 0 | 2017-01-03 |
| 4 | 4 | 4 | 1 | 0 | 2017-01-04 |
+−−−−−−−−−+−−−−−−−−+−−−−+−−−−−−−+−−−−−−−+−−−−−−−−−−−−+
But we've ignored the date criteria required by the question:
...filtered by a date range applied to the last row in the chain.
To do that without building a massive temporary result set, we have to work backward: Instead of selecting the starting point (the first entry in a chain, Replaces IS NULL), we need to select the ending point (the last entry in a chain, ReplacedBy IS NULL), and then invert our logic working back through the chain. It's largely a matter of:
Swapping FirstId with LastId
Swapping Replaces with ReplacedBy (convenient the table had both!)
Using MIN to get the first ID in the chain rather than MAX to get the last
Using d.Depth - 1 rather than d.Depth + 1
Then fixing-up Depth based on Links once we know it in our final select, to get those nice values where 0 = first link rather than some varying negative number: o.Links + d.Depth - 1 AS Depth
All of which gives us:
WITH Data AS (
SELECT Id AS LastId, Id, TStamp, Replaces, ReplacedBy, 0 AS Depth
FROM Thing
WHERE ReplacedBy IS NULL AND Replaces IS NOT NULL
-- Filtering by date of last entry would go here
UNION ALL
SELECT d.LastId, t.Id, t.TStamp, t.Replaces, t.ReplacedBy, d.Depth - 1
FROM Data d
JOIN Thing t ON t.ReplacedBy = d.Id
),
Overview AS (
SELECT LastId, MIN(Id) AS FirstId, COUNT(*) AS Links
FROM Data
GROUP BY
LastId
)
SELECT o.FirstId, d.LastId, d.Id, o.Links, o.Links + d.Depth - 1 AS Depth, d.TStamp
FROM Data d
CROSS APPLY (
SELECT FirstId, Links
FROM Overview
WHERE LastId = d.LastId
) o
ORDER BY
o.FirstId, d.Depth
;
So for instance, if we used
AND TStamp BETWEEN '2017-01-12' AND '2017-02-01'
where I have
-- Filtering by date of last entry would go here
above, with our sample data we'd get this result:
+−−−−−−−−−+−−−−−−−−+−−−−+−−−−−−−+−−−−−−−+−−−−−−−−−−−−+
| FirstId | LastId | Id | Links | Depth | TStamp |
+−−−−−−−−−+−−−−−−−−+−−−−+−−−−−−−+−−−−−−−+−−−−−−−−−−−−+
| 2 | 22 | 2 | 3 | 0 | 2017−01−02 |
| 2 | 22 | 12 | 3 | 1 | 2017−01−12 |
| 2 | 22 | 22 | 3 | 2 | 2017−01−13 |
+−−−−−−−−−+−−−−−−−−+−−−−+−−−−−−−+−−−−−−−+−−−−−−−−−−−−+
...because the last link the Id = 1 chain is outside the date range, so we don't include it.
This is a little tricky. Arrange the CTE to start at the beginning of each list. That makes the subsequent processing easier:
WITH Data AS (
SELECT Id as FirstId, Id, TStamp, Replaces, ReplacedBy, 0 AS Depth
FROM Thing t
WHERE NOT EXISTS (SELECT 1 FROM Thing t2 WHERE t2.ReplacedBy = t.id)
UNION ALL
SELECT d.FirstId, t.Id, t.TStamp, t.Replaces, t.ReplacedBy, d.Depth + 1
FROM Data d JOIN
Thing t
ON t.Replaces = d.Id
)
SELECT d.*,
FIRST_VALUE(id) OVER (PARTITION BY FirstId ORDER BY Depth DESC) as LastId
FROM Data d;
Then, you can use FIRST_VALUE() with a reverse sort to get the last value in the chain.
This returns chains that have no links. You can add a filter to remove these.
Based on the product and product key, update the column ord_by. There should be only one min and max for a product and product_key .
E.g: Table
+-------------+---------+-------+--------+
| Product_key | product | price | ord_by |
+-------------+---------+-------+--------+
| 1 | ABC | 10 | |
| 1 | ABC | 10 | |
| 1 | ABC | 20 | |
| 1 | ABC | 100 | |
| 1 | ABC | 100 | |
| 2 | EFG | 20 | |
| 2 | EFG | 40 | |
| 3 | ABC | 100 | |
+-------------+---------+-------+--------+
Expected output:
+-------------+---------+-------+--------+
| Product_key | product | price | ord_by |
+-------------+---------+-------+--------+
| 1 | ABC | 10 | Min |
| 1 | ABC | 10 | Mid |
| 1 | ABC | 20 | Mid |
| 1 | ABC | 100 | Mid |
| 1 | ABC | 100 | Max |
| 2 | EFG | 20 | Min |
| 2 | EFG | 40 | Max |
| 3 | ABC | 100 | None |
+-------------+---------+-------+--------+
My try :
;WITH ord_cte
AS (
SELECT product
,product_key
,max(price) as max_price
,min(price) as min_price
FROM t_prod_ord
group by product,product_key
)
UPDATE t1
SET ord_by = case
when t2.max_price =t2.min_price then 'none'
when t2.max_price=t1.price then 'max'
when t2.min_price=t1.price then 'min'
else 'mid' end
FROM t_prod_ord t1
INNER JOIN ord_cte t2 ON t1.product_key = t2.product_key and t1.product=t2.product
using this query it is updating more than one max and min value for column ord_by.
Generate row number for each Product_key order by Price in both ASC and DESC order. Then use the row number in CASE statement to find the Min/Max values
Count() Over() aggregate window function will help you find the total count of each Product_key which we can use it for finding None
Here is one way
;WITH cte
AS (SELECT *,
Row_number()OVER(PARTITION BY Product_key ORDER BY price) AS Min_KEY,
Row_number()OVER(PARTITION BY Product_key ORDER BY price DESC) AS Max_KEY,
Count(1)OVER(partition BY Product_key) AS cnt
FROM Yourtable)
SELECT Product_key,
product,
price,
CASE
WHEN cnt = 1 THEN 'None'
WHEN Min_KEY = 1 THEN 'Min'
WHEN Max_Key = 1 THEN 'Max'
ELSE 'Mid'
END
FROM cte
Another way to do with out cte...
SELECT [Product_key],
[product],
[price],
CASE
WHEN Max(RN)
OVER(
PARTITION BY PRODUCT_KEY, PRODUCT
)=1 AND RN=1 THEN 'NONE'
WHEN Min(RN)
OVER(
PARTITION BY PRODUCT_KEY, PRODUCT
) = RN THEN 'MIN'
WHEN Max(RN)
OVER(
PARTITION BY PRODUCT_KEY, PRODUCT
) = RN THEN 'MAX'
ELSE 'MID'
END ORDER_BY
FROM (SELECT *,
Row_number()
OVER(
PARTITION BY PRODUCT_KEY, PRODUCT
ORDER BY PRICE) RN
FROM TABLE1)Z
Let's say I have a table named tableA having a data of
| col1 | col2 |
| 1 | 5 |
| 1 | 6 |
| 1 | 7 |
| 2 | 1 |
| 2 | 2 |
| 2 | 3 |
| 2 | 4 |
| 3 | 3 |
| 3 | 2 |
| 3 | 1 |
Then what I would like to get is the last 2 occurrences of each unique value of col1. The result would be
| col1 | col2 |
| 1 | 6 |
| 1 | 7 |
| 2 | 3 |
| 2 | 4 |
| 3 | 2 |
| 3 | 1 |
Is there a single query to get this result?
You can use ROW_NUMBER
WITH CTE AS(
SELECT *, rn = ROW_NUMBER() OVER(PARTITION BY col1 ORDER BY col2 DESC)
FROM tbl
)
SELECT
col1, col2
FROM CTE
WHERE rn <= 2
Just expanding on Felix's answer, assuming there's an ID column: http://www.sqlfiddle.com/#!3/04a5e/3/0
WITH CTE AS(
SELECT *, rn = ROW_NUMBER() OVER(PARTITION BY cola ORDER BY id DESC)
FROM ta
)
SELECT
cola, colb
FROM CTE
WHERE rn <= 2
order by id
Need to reorder by ID to keep the correct order, plus ordering in the row_number() by the ID because col2 isn't always incremental.