I have this table:
Reply_ID | Fk_Post_ID
10 | 5
9 | 6
8 | 5
7 | 9
6 | 5
5 | 9
4 | 7
I need a query retrieves records in the following order pattern. it searches for the record with the highest reply_ID then retrieves all records having the same Fk_Post_ID. something like this:
Reply_ID | Fk_Post_ID
10 | 5
8 | 5
6 | 5
9 | 6
7 | 9
5 | 9
4 | 7
CREATE TABLE #YourTable (
Reply_ID INT,
fk_Post_ID INT
)
INSERT INTO #YourTable VALUES (10, 5)
INSERT INTO #YourTable VALUES (9, 6)
INSERT INTO #YourTable VALUES (8, 5)
INSERT INTO #YourTable VALUES (7, 9)
INSERT INTO #YourTable VALUES (6, 5)
SELECT
t1.Reply_ID,
t1.fk_Post_ID
FROM
#YourTable t1 JOIN (
SELECT
MAX(Reply_ID) AS Max_Reply_ID,
fk_Post_ID
FROM #YourTable
GROUP BY fk_Post_ID
) t2 ON t2.fk_Post_ID = t1.fk_Post_ID
ORDER BY
t2.Max_Reply_ID DESC,
t1.Reply_ID DESC
Sql Fiddle Here
You could use a CASE in the ORDER BY:
....
ORDER BY CASE WHEN Fk_Post_ID=(
SELECT MIN(Fk_Post_ID)
FROM dbo.Table
WHERE Reply_ID=(SELECT MAX(Reply_ID)FROM dbo.Table)
) THEN 0 ELSE 1 END ASC
, Reply_ID DESC
, Fk_Post_ID ASC
Here's the fiddle: http://sqlfiddle.com/#!3/45f20/7/0
If your DBMS has window functions then this will also solve it:
Select
Reply_ID,
FK_Post_ID
From
yourTable a
Order By
Max(Reply_ID) Over (Partition By FK_Post_ID) Desc,
Reply_ID Desc
http://sqlfiddle.com/#!3/4be0c/9/0
Related
I saw many questions related to a recursive query but couldn't find any that shows how to use it based on a reference table.
I have a MasterTable where Id, ParentId columns are establishing the parent/child relation.
I have a SubTable where I have a bunch of Ids which could be a parent Id or child Id.
I would like to retrieve all related records (parent or child, recursively) from the MasterTable based on given SubTable
Current output:
id parentId
----------- -----------
1 NULL
2 1
3 1
4 NULL
5 4
6 5
7 6
Expected output
id parentId
----------- -----------
1 NULL
2 1
3 1
4 NULL
5 4
6 5
7 6
8 9
9 NULL
10 NULL
11 10
13 11
14 10
15 16
16 NULL
Comparison of actual vs expected:
Code:
DECLARE #MasterTable TABLE
(
id INT NOT NULL,
parentId INT NULL
);
DECLARE #SubTable TABLE
(
id INT NOT NULL
);
INSERT INTO #MasterTable (id, parentId)
VALUES (1, NULL), (2, 1), (3, 1), (4, NULL), (5, 4), (6, 5),
(7, 6), (8, 9), (9, NULL), (10, NULL), (11, 10), (12, NULL),
(13, 11), (13, 11), (14, 10), (15, 16), (16, NULL);
INSERT INTO #SubTable (id)
VALUES (1), (2), (3), (4), (6), (5), (7),
(8), -- it does not show
(13), -- it does not show
(15); -- it does not show
/* beside 8,13,15 it should add 9,11,14 and 10,16 */
;WITH cte AS
(
SELECT
mt1.id,
mt1.parentId
FROM
#MasterTable AS mt1
WHERE
mt1.parentId IS NULL
AND EXISTS (SELECT NULL AS empty
FROM #SubTable AS st
WHERE st.Id = mt1.id)
UNION ALL
SELECT
mt2.id,
mt2.parentId
FROM
#MasterTable AS mt2
INNER JOIN
cte AS c1 ON c1.id = mt2.parentId
)
SELECT DISTINCT
c2.id,
c2.parentId
FROM
cte AS c2
ORDER BY
id;
Is the following query suitable for the issue in question?
with
r as(
select
m.*, iif(m.parentid is null, 1, 0) p_flag
from #MasterTable m
join #SubTable s
on s.id = m.id
union all
select
m.*, iif(m.parentid is null, 1, r.p_flag)
from r
join #MasterTable m
on (r.p_flag = 1 and m.parentid = r.id) or
(r.p_flag = 0 and r.parentid = m.id)
)
select distinct
id, parentid
from r
order by id;
Output:
| id | parentid |
+----+----------+
| 1 | NULL |
| 2 | 1 |
| 3 | 1 |
| 4 | NULL |
| 5 | 4 |
| 6 | 5 |
| 7 | 6 |
| 8 | 9 |
| 9 | NULL |
| 10 | NULL |
| 11 | 10 |
| 13 | 11 |
| 14 | 10 |
| 15 | 16 |
| 16 | NULL |
Test it online with rextester.com.
;WITH cte
AS (
SELECT mt1.id,
mt1.parentId
FROM #MasterTable AS mt1
WHERE mt1.parentId IS NULL
UNION ALL
SELECT mt2.id,
mt2.parentId
FROM #MasterTable AS mt2
INNER JOIN cte AS c1
ON c1.id = mt2.parentId
)
SELECT DISTINCT c2.id,
c2.parentId
FROM cte AS c2
where
EXISTS (
SELECT 1 AS empty FROM #SubTable AS st
WHERE ( st.Id = c2.id or st.Id = c2.parentId)
)
or
EXISTS (
SELECT 1 AS empty FROM #MasterTable AS mt
WHERE ( c2.Id = mt.parentId or c2.parentId = mt.parentId)
)
ORDER BY id;
You may try this....
; with cte as(
select distinct mas.id, mas.parentId, iif(mas.parentid is null, 1, 0) PId
from #MasterTable mas inner join #SubTable sub
on sub.id in(mas.id, mas.parentid) ----- create top node having parentid is null
union all
select mas.id, mas.parentId, ct.PId
from cte ct inner join #MasterTable mas
on (ct.PId = 1 and mas.parentid = ct.id) or
(ct.PId = 0 and ct.parentid = mas.id) ----- create child node for correspoding parentid created above
)
select distinct id, parentid from cte order by id
option (MAXRECURSION 100); ---- Add Maxrecursion to prevent the infinite loop
You can find this link for more info on recursive query in SQL link. In this link see Example E or above.
This question already has answers here:
Select first row in each GROUP BY group?
(20 answers)
Closed 6 years ago.
I have a table in my database that I am using a SQL query to retrieve data from. In my query, I am replacing some text and using integers. The query returns the data below:
user_id | event_code | total_bookmarks | total_folders | folder_depth | ts
0 8 34 6 1 128926
0 8 35 6 1 129001
4 8 18 2 1 123870
6 8 30 2 1 130099
6 8 30 2 1 132000
6 8 30 2 1 147778
The query I am using is:
SELECT
user_id,
event_code,
CAST(REPLACE(data1, 'total bookmarks', '') AS INTEGER) as total_bookmarks,
CAST(REPLACE(data2, 'folders', '') AS INTEGER) as total_folders,
CAST(REPLACE(data3, 'folder depth ', '') AS INTEGER) as folder_depth,
timestamp AS ts
FROM events
WHERE event_code = 8
What do I need to add to my query in order to only select the rows for each unique user_id with the max ts (timestamp) for each id? I tried MAX(timestamp), but I get two rows returned for the same ID if the total_bookmark is different (example: user_id 0 having 34 in one row, and 35 in another) I want the table to look like this:
user_id | event_code | total_bookmarks | total_folders | folder_depth | ts
0 8 34 6 1 129001
4 8 18 2 1 123870
6 8 30 2 1 147778
Declare #table table (user_id int, event_code int, total_bookmarks int, total_folders int, folder_depth int, ts decimal(18,0))
Insert into #table (user_id , event_code , total_bookmarks , total_folders , folder_depth , ts)
Values (0,8,34,6,1,128926),
(0,8,34,6,1,129001),
(4, 8, 18 , 2, 1, 123870),
(6, 8, 30, 2, 1, 130099),
(6, 8, 30, 2, 1, 132000),
(6, 8, 30, 2, 1, 147778)
Select * from #table
Select user_id,event_code,total_bookmarks,total_folders,folder_depth,ts
From (
Select RANK() over (Partition by user_id
Order by ts desc
) as Rank,
user_id,event_code,total_bookmarks,total_folders,folder_depth,ts
From #table
) D1
Where D1.Rank = 1
i have a self related table myTable like :
ID | RefID
----------
1 | NULL
2 | 1
3 | 2
4 | NULL
5 | 2
6 | 5
7 | 5
8 | NULL
9 | 7
i need to get leaf rows on any depth
based on the table above, the result must be :
ID | RefID
----------
3 | 2
4 | NULL
6 | 5
8 | NULL
9 | 7
thank you
PS: the depth may vary , here is very small example
Try:
SELECT id,
refid
FROM mytable t
WHERE NOT EXISTS (SELECT 1
FROM mytable
WHERE refid = t.id)
DECLARE #t TABLE (id int NOT NULL, RefID int NULL);
INSERT #t VALUES (1, NULL), (2, 1), (3, 2), (5, NULL),
(6, 5), (4, NULL), (7, 5), (8, NULL), (9, 8), (10, 7);
WITH CTE AS
(
-- top level
SELECT id, RefID, id AS RootId, 0 AS CTELevel FROM #t WHERE REfID IS NULL
UNION ALL
SELECT T.id, T.RefID, RootId, CTELevel + 1 FROM #t T JOIN CTE ON T.RefID = CTE.id
), Leafs AS
(
SELECT
id, RefID, DENSE_RANK() OVER (PARTITION BY CTE.RootId ORDER BY CTELevel DESC) AS Rn
FROM CTE
)
SELECT
id, RefID
FROM
Leafs
WHERE
rn = 1
select ID, RefId
from myTable t1 left join myTable t2 on t1.ID = t2.RefID
where t2.RefID is null
try this:
SELECT *
FROM
my_table
WHERE
id NOT IN
(
SELECT DISTINCT
refId
FROM
my_table
WHERE
refId IS NOT NULL
)
I have a table with an id as the primary key, and a description as another field.
I want to first select the records that have the id<=4, sorted by description, then I want all the other records (id>4), sorted by description. Can't get there!
select id, descr
from t
order by
case when id <= 4 then 0 else 1 end,
descr
select *, id<=4 as low from table order by low, description
You may want to use an id <= 4 expression in your ORDER BY clause:
SELECT * FROM your_table ORDER BY id <= 4 DESC, description;
Test case (using MySQL):
CREATE TABLE your_table (id int, description varchar(50));
INSERT INTO your_table VALUES (1, 'c');
INSERT INTO your_table VALUES (2, 'a');
INSERT INTO your_table VALUES (3, 'z');
INSERT INTO your_table VALUES (4, 'b');
INSERT INTO your_table VALUES (5, 'g');
INSERT INTO your_table VALUES (6, 'o');
INSERT INTO your_table VALUES (7, 'c');
INSERT INTO your_table VALUES (8, 'p');
Result:
+------+-------------+
| id | description |
+------+-------------+
| 2 | a |
| 4 | b |
| 1 | c |
| 3 | z |
| 7 | c |
| 5 | g |
| 6 | o |
| 8 | p |
+------+-------------+
8 rows in set (0.00 sec)
Related post:
Using MySql, can I sort a column but have 0 come last?
select id, description
from MyTable
order by case when id <= 4 then 0 else 1 end, description
You can use UNION
SELECT * FROM (SELECT * FROM table1 WHERE id <=4 ORDER by description)aaa
UNION
SELECT * FROM (SELECT * FROM table1 WHERE id >4 ORDER by description)bbb
OR
SELECT * FROM table1
ORDER BY
CASE WHEN id <=4 THEN 0
ELSE 1
END, description
For following data:
date|value|check
2009 | 5 | 1
2008 | 5 | 1
2007 | 5 | 1
2006 | 5 | 0
2005 | 5 | 0
2004 | 5 | 1
2003 | 5 | 1
2002 | 5 | 1
I need to select all rows from 2009 back until first occurrence of 0 in check column:
date|value|check
2009 | 5 | 1
2008 | 5 | 1
2007 | 5 | 1
I tried with the lag function, but I was only able to check a month back.
I am working on Oracle 10g.
UPDATE:
All seems to work well, my test data set is too small to say anything about the performance differences.
SELECT * FROM mytable where date > (
SELECT max(date) FROM mytable where check = 0
)
SELECT *
FROM (
SELECT m.*,
MIN(CASE WHEN check = 0 THEN 0 ELSE 1 END) OVER (ORDER BY date DESC)) AS mn
FROM mytable
)
WHERE mn = 1
or even better:
SELECT *
FROM (
SELECT m.*, ROW_NUMBER() OVER (ORDER BY mydate DESC) AS rn
FROM mytable m
ORDER BY
mydate DESC
)
WHERE rownum = DECODE(check, 0, NULL, rn)
ORDER BY
mydate DESC
The latter query will actually stop scanning as soon as it encounters the first zero in check.
DECLARE #mytable TABLE (date integer, [value] integer, [check] integer)
INSERT INTO #mytable VALUES (2009, 5, 1)
INSERT INTO #mytable VALUES (2008, 5, 1)
INSERT INTO #mytable VALUES (2007, 5, 1)
INSERT INTO #mytable VALUES (2006, 5, 0)
INSERT INTO #mytable VALUES (2005, 5, 0)
INSERT INTO #mytable VALUES (2004, 5, 1)
INSERT INTO #mytable VALUES (2003, 5, 1)
INSERT INTO #mytable VALUES (2002, 5, 1)
SELECT *
FROM #mytable
WHERE date > (SELECT MAX(date) FROM #mytable WHERE [Check] = 0)