I am trying to write a query that will select all of the numbers in my table, but those numbers with duplicates i want to append something on the end that shows it as a duplicate. However I am not sure how to do this.
Here is an example of the table
TableA
ID Number
1 1
2 2
3 2
4 3
5 4
SELECT statement output would be like this.
Number
1
2
2-dup
3
4
Any insight on this would be appreciated.
if you mysql version didn't support window function. you can try to write a subquery to make row_number then use CASE WHEN to judgement rn > 1 then mark dup.
create table T (ID int, Number int);
INSERT INTO T VALUES (1,1);
INSERT INTO T VALUES (2,2);
INSERT INTO T VALUES (3,2);
INSERT INTO T VALUES (4,3);
INSERT INTO T VALUES (5,4);
Query 1:
select t1.id,
(CASE WHEN rn > 1 then CONCAT(Number,'-dup') ELSE Number END) Number
from (
SELECT *,(SELECT COUNT(*)
FROM T tt
where tt.Number = t1.Number and tt.id <= t1.id
) rn
FROM T t1
)t1
Results:
| id | Number |
|----|--------|
| 1 | 1 |
| 2 | 2 |
| 3 | 2-dup |
| 4 | 3 |
| 5 | 4 |
If you can use window function you can use row_number with window function to make rownumber by Number.
select t1.id,
(CASE WHEN rn > 1 then CONCAT(Number,'-dup') ELSE Number END) Number
from (
SELECT *,row_number() over(partition by Number order by id) rn
FROM T t1
)t1
sqlfiddle
I made a list of all the IDs that weren't dups (left join select) and then compared them to the entire list(case when):
select
case when a.id <> b.min_id then cast(a.Number as varchar(6)) + '-dup' else cast(a.Number as varchar(6)) end as Number
from table_a
left join (select MIN(b.id) min_id, Number from table_a b group by b.number)b on b.number = a.number
I did this in MS SQL 2016, hope it works for you.
This creates the table used:
insert into table_a (ID, Number)
select 1,1
union all
select 2,2
union all
select 3,2
union all
select 4,3
union all
select 5,4
Question
Please consider the following table:
+--------------+--------+--------+
| transactionID | Sgroup | Rgroup |
+--------------+--------+--------+
| 1 | A | I |
| 1 | A | J |
| 2 | B | B |
| 2 | B | K |
+--------------+--------+--------+
For each transactionID (2 rows are associated with ID 1, two rows with ID 2) I want to select the row for which Sgroup = Rgroup, if any row within a transactionID satisfies the condition. Otherwise, I want to select a row at random. For each transactionID at most one row satisfies Sgroup = Rgroup. How can I do this?
Attempted Solution
I know how to select rows for which the condition Sgroup = Rgroup is fulfilled as follows:
SELECT *
FROM Transaction
WHERE Sgroup = Rgroup;
+---------------+--------+--------+
| transactionID | Sgroup | Rgroup |
+---------------+--------+--------+
| 2 | B | B |
+---------------+--------+--------+
I also know how to chose a row randomly (thanks to this question) if the condition is not fulfilled as follows:
SELECT * FROM
(SELECT *
FROM Transaction
WHERE NOT transactionID IN
(SELECT transactionID
FROM Transaction
WHERE Sgroup = Rgroup)
ORDER BY RAND()) AS temp
GROUP BY temp.transactionID;
+---------------+--------+--------+
| transactionID | Sgroup | Rgroup |
+---------------+--------+--------+
| 1 | A | I |
+---------------+--------+--------+
How can I combine these two expressions into one? I tried working with a CASE expression I didn't get far. Can somebody kindly suggest a solution?
Example Code Here is the code to generate the table:
CREATE DATABASE MinimalExample;
USE MinimalExample;
CREATE TABLE Transaction (
transactionID int,
Sgroup nvarchar(1),
Rgroup nvarchar(1)
);
INSERT INTO Transaction VALUES
(1,'A','I'),
(1,'A','J'),
(2,'B','B'),
(2,'B','K');
I think variables might be the simplest solution if you really mean "random":
select t.*
from (select t.*,
(#rn := if(#i = transactionID, #rn + 1,
if(#i := transactionID, 1, 1)
)
) as rn
from (select t.*
from t
order by transactionID, (sgroup = rgroup) desc, rand()
) t cross join
(select #i := -1, #rn := 0) params
) t
where rn = 1;
If by "random" you mean "arbitrary", you can use this quick-and-dirty trick:
(select t.*
from t
where sgroup = rgroup
)
union all
(select t.*
from t
where not exists (select 1 from t t2 where t2.id = t.id and t2.sgroup = t2.rgroup)
group by transactionID
);
This uses the dreaded select * with group by, something which I strongly discourage using under almost all circumstances. However, in this case, you are specifically trying to reduce each group to an indeterminate row, so it doesn't seem quite so bad. I will note that MySQL does not guarantee that the columns in the result set all come from the same row, although in practice they do.
Finally, if you had a unique primary key on each row, you could use probably the simplest solution:
select t.*
from t
where t.id = (select t2.id
from t t2
where t2.transactionID = t.transactionID
order by (rgroup = sgroup) desc, rand()
);
If I have a table:
id1 id2 count
A A 1
A B 2
A C 1
B A 3
B B 1
B C 2
C A 3
C B 2
C C 1
What I want after deleting:
id1 id2 count
A A 1
A B 2
A C 1
B B 1
B C 2
C C 1
which means if I have A(id1) --> B(id2) then delete B(id1) --> A(id2). same as B(id1) --> C(id2) then delete the row C(id1) --> B(id2)
Thank you for ur help!
In this case we analyze Target.id1 > Target.id2 mean case like (B, A, ??) where B > A
this also ignore cases like (A, A, ??)
Then use self left join to try find another row with (A, B, ??)
If we found a match then Source.id1 IS NOT NULL and we delete
SQL Fiddle Demo
DELETE Target
FROM Table1 Target
LEFT JOIN Table1 Source
ON Target.`id1` = Source.`id2`
AND Target.`id2` = Source.`id1`
AND Target.`id1` > Target.`id2`
WHERE Source.`id1` IS NOT NULL;
OUTPUT
| id1 | id2 | count |
|-----|-----|-------|
| A | A | 1 |
| A | B | 2 |
| A | C | 1 |
| B | B | 1 |
| B | C | 2 |
| C | C | 1 |
Should be something like:
DELETE FROM 'myTable'
WHERE STRCMP(id1, id2) > 0;
STRCMP function can compare the strings and return an int. From there it should be easy - something very similar to the above. If you have further trouble let me know.
It looks like what you are saying is...
If there is a (id1,id2) tuple in the table with values e.g. (a,b), and there is another tuple (b,a) that consists of the the same values, but swapped in the columns, you want to remove one of those tuples. It looks like the one you want to remove is the one that has the "greater" value in the first column.
First, identify the "duplicate" tuples.
For now, we'll ignore the tuples where the values of id1 and id2 are the same, e.g. (a,a).
SELECT s.id1
, s.id2
FROM mytable s
WHERE s.id1 > s.id2
AND EXISTS ( SELECT 1
FROM mytable r
WHERE r.id1 = s.id2
AND r.id2 = s.id1
)
ORDER BY s.id1, s.id2
If that returns the set of rows you want to remove, we can convert that into a DELETE. To do that, we need to change that query into an inline view,
We can re-write that to be like this, verify we get equivalent results.
SELECT o.id1, o.id2
FROM ( SELECT q.id1, q.id2
FROM ( SELECT s.id1, s.id2
FROM mytable s
WHERE s.id1 > s.id2
AND EXISTS ( SELECT 1
FROM mytable r
WHERE r.id1 = s.id2
AND r.id2 = s.id1
)
) q
GROUP BY q.id1, q.id2
) p
JOIN mytable o
ON o.id1 = p.id1
AND o.id2 = p.id2
ORDER BY o.id1, o.id2
Then we can convert that to a DELETE statement, replacing SELECT o.id1, o.id2 WITH DELETE o.* and removing the ORDER BY...
DELETE o.*
FROM ( SELECT q.id1, q.id2
FROM ( SELECT s.id1, s.id2
FROM mytable s
WHERE s.id1 > s.id2
AND EXISTS ( SELECT 1
FROM mytable r
WHERE r.id1 = s.id2
AND r.id2 = s.id1
)
) q
GROUP BY q.id1, q.id2
) p
JOIN mytable o
ON o.id1 = p.id1
AND o.id2 = p.id2
I am trying to get the avg of an item so I am using a subquery.
Update: I should have been clearer initially, but i want the avg to be for the last 5 items only
First I started with
SELECT
y.id
FROM (
SELECT *
FROM (
SELECT *
FROM products
WHERE itemid=1
) x
ORDER BY id DESC
LIMIT 15
) y;
Which runs but is fairly useless as it just shows me the ids.
I then added in the below
SELECT
y.id,
(SELECT AVG(deposit) FROM (SELECT deposit FROM products WHERE id < y.id ORDER BY id DESC LIMIT 5)z) AVGDEPOSIT
FROM (
SELECT *
FROM (
SELECT *
FROM products
WHERE itemid=1
) x
ORDER BY id DESC
LIMIT 15
) y;
When I do this I get the error Unknown column 'y.id' in 'where clause', upon further reading here I believe this is because when the queries go down to the next level they need to be joined?
So I tried the below ** removed un needed suquery
SELECT
y.id,
(SELECT AVG(deposit) FROM (
SELECT deposit
FROM products
INNER JOIN y as yy ON products.id = yy.id
WHERE id < yy.id
ORDER BY id DESC
LIMIT 5)z
) AVGDEPOSIT
FROM (
SELECT *
FROM products
WHERE itemid=1
ORDER BY id DESC
LIMIT 15
) y;
But I get Table 'test.y' doesn't exist. Am I on the right track here? What do I need to change to get what I am after here?
The example can be found here in sqlfiddle.
CREATE TABLE products
(`id` int, `itemid` int, `deposit` int);
INSERT INTO products
(`id`, `itemid`, `deposit`)
VALUES
(1, 1, 50),
(2, 1, 75),
(3, 1, 90),
(4, 1, 80),
(5, 1, 100),
(6, 1, 75),
(7, 1, 75),
(8, 1, 90),
(9, 1, 90),
(10, 1, 100);
Given my data in this example, my expected result is below, where there is a column next to each ID that has the avg of the previous 5 deposits.
id | AVGDEPOSIT
10 | 86 (deposit value of (id9+id8+id7+id6+id5)/5) to get the AVG
9 | 84
8 | 84
7 | 84
6 | 79
5 | 73.75
I'm not an MySQL expert (in MS SQL it could be done easier), and your question looks a bit unclear for me, but it looks like you're trying to get average of previous 5 items.
If you have Id without gaps, it's easy:
select
p.id,
(
select avg(t.deposit)
from products as t
where t.itemid = 1 and t.id >= p.id - 5 and t.id < p.id
) as avgdeposit
from products as p
where p.itemid = 1
order by p.id desc
limit 15
If not, then I've tri tried to do this query like this
select
p.id,
(
select avg(t.deposit)
from (
select tt.deposit
from products as tt
where tt.itemid = 1 and tt.id < p.id
order by tt.id desc
limit 5
) as t
) as avgdeposit
from products as p
where p.itemid = 1
order by p.id desc
limit 15
But I've got exception Unknown column 'p.id' in 'where clause'. Looks like MySQL cannot handle 2 levels of nesting of subqueries.
But you can get 5 previous items with offset, like this:
select
p.id,
(
select avg(t.deposit)
from products as t
where t.itemid = 1 and t.id > coalesce(p.prev_id, -1) and t.id < p.id
) as avgdeposit
from
(
select
p.id,
(
select tt.id
from products as tt
where tt.itemid = 1 and tt.id <= p.id
order by tt.id desc
limit 1 offset 6
) as prev_id
from products as p
where p.itemid = 1
order by p.id desc
limit 15
) as p
sql fiddle demo
This is my solution. It is easy to understand how it works, but at the same time it can't be optimized much since I'm using some string functions, and it's far from standard SQL. If you only need to return a few records, it could be still fine.
This query will return, for every ID, a comma separated list of previous ID, ordered in ascending order:
SELECT p1.id, p1.itemid, GROUP_CONCAT(p2.id ORDER BY p2.id DESC) previous_ids
FROM
products p1 LEFT JOIN products p2
ON p1.itemid=p2.itemid AND p1.id>p2.id
GROUP BY
p1.id, p1.itemid
ORDER BY
p1.itemid ASC, p1.id DESC
and it will return something like this:
| ID | ITEMID | PREVIOUS_IDS |
|----|--------|-------------------|
| 10 | 1 | 9,8,7,6,5,4,3,2,1 |
| 9 | 1 | 8,7,6,5,4,3,2,1 |
| 8 | 1 | 7,6,5,4,3,2,1 |
| 7 | 1 | 6,5,4,3,2,1 |
| 6 | 1 | 5,4,3,2,1 |
| 5 | 1 | 4,3,2,1 |
| 4 | 1 | 3,2,1 |
| 3 | 1 | 2,1 |
| 2 | 1 | 1 |
| 1 | 1 | (null) |
then we can join the result of this query with the products table itself, and on the join condition we can use FIND_IN_SET(src, csvalues) that return the position of the src string inside the comma separated values:
ON FIND_IN_SET(id, previous_ids) BETWEEN 1 AND 5
and the final query looks like this:
SELECT
list_previous.id,
AVG(products.deposit)
FROM (
SELECT p1.id, p1.itemid, GROUP_CONCAT(p2.id ORDER BY p2.id DESC) previous_ids
FROM
products p1 INNER JOIN products p2
ON p1.itemid=p2.itemid AND p1.id>p2.id
GROUP BY
p1.id, p1.itemid
) list_previous LEFT JOIN products
ON list_previous.itemid=products.itemid
AND FIND_IN_SET(products.id, previous_ids) BETWEEN 1 AND 5
GROUP BY
list_previous.id
ORDER BY
id DESC
Please see fiddle here. I won't recommend using this trick for big tables, but for small sets of data it is fine.
This is maybe not the simplest solution, but it does do the job and is an interesting variation and in my opinion transparent. I simulate the analytical functions that I know from Oracle.
As we do not assume the id to be consecutive the counting of the rows is simulated by increasing #rn each row. Next products table including the rownum is joint with itself and only the rows 2-6 are used to build the average.
select p2id, avg(deposit), group_concat(p1id order by p1id desc), group_concat(deposit order by p1id desc)
from ( select p2.id p2id, p1.rn p1rn, p1.deposit, p2.rn p2rn, p1.id p1id
from (select p.*,#rn1:=#rn1+1 as rn from products p,(select #rn1 := 0) r) p1
, (select p.*,#rn2:=#rn2+1 as rn from products p,(select #rn2 := 0) r) p2 ) r
where p2rn-p1rn between 1 and 5
group by p2id
order by p2id desc
;
Result:
+------+--------------+---------------------------------------+------------------------------------------+
| p2id | avg(deposit) | group_concat(p1id order by p1id desc) | group_concat(deposit order by p1id desc) |
+------+--------------+---------------------------------------+------------------------------------------+
| 10 | 86.0000 | 9,8,7,6,5 | 90,90,75,75,100 |
| 9 | 84.0000 | 8,7,6,5,4 | 90,75,75,100,80 |
| 8 | 84.0000 | 7,6,5,4,3 | 75,75,100,80,90 |
| 7 | 84.0000 | 6,5,4,3,2 | 75,100,80,90,75 |
| 6 | 79.0000 | 5,4,3,2,1 | 100,80,90,75,50 |
| 5 | 73.7500 | 4,3,2,1 | 80,90,75,50 |
| 4 | 71.6667 | 3,2,1 | 90,75,50 |
| 3 | 62.5000 | 2,1 | 75,50 |
| 2 | 50.0000 | 1 | 50 |
+------+--------------+---------------------------------------+------------------------------------------+
SQL Fiddle Demo: http://sqlfiddle.com/#!2/c13bc/129
I want to thank this answer on how to simulate analytical functions in mysql: MySQL get row position in ORDER BY
It looks like you just want:
SELECT
id,
(SELECT AVG(deposit)
FROM (
SELECT deposit
FROM products
ORDER BY id DESC
LIMIT 5) last5
) avgdeposit
FROM products
The inner query gets the last 5 rows added to product, the query that wraps that gets the average for their deposits.
I'm going to simplify your query a bit so I can explain it.
SELECT
y.id,
(
SELECT AVG(deposit) FROM
(
SELECT deposit
FROM products
LIMIT 5
) z
) AVGDEPOSIT
FROM
(
SELECT *
FROM
(
SELECT *
FROM products
) x
LIMIT 15
) y;
My guess would be that you just need to insert some AS keywords in there. I'm sure someone else will come up with something more elegant, but for now you can try it out.
SELECT
y.id,
(
SELECT AVG(deposit) FROM
(
SELECT deposit
FROM products
LIMIT 5
) z
) AS AVGDEPOSIT
FROM
(
SELECT *
FROM
(
SELECT *
FROM products
) AS x
LIMIT 15
) y;
Here's one way to do it in MySQL:
SELECT p.id
, ( SELECT AVG(deposit)
FROM ( SELECT #rownum:=#rownum+1 rn, deposit, id
FROM ( SELECT #rownum:=0 ) r
, products
ORDER BY id ) t
WHERE rn BETWEEN p.rn-5 AND p.rn-1 ) avgdeposit
FROM ( SELECT #rownum1:=#rownum1+1 rn, id
FROM ( SELECT #rownum1:=0 ) r
, products
ORDER BY id ) p
WHERE p.rn >= 5
ORDER BY p.rn DESC;
It's a shame MySQL doesn't support the WITH clause or windowing functions. Having both would greatly simplify the query to the following:
WITH tbl AS (
SELECT id, deposit, ROW_NUMBER() OVER(ORDER BY id) rn
FROM products
)
SELECT id
, ( SELECT AVG(deposit)
FROM tbl
WHERE rn BETWEEN t.rn-5 AND t.rn-1 )
FROM tbl t
WHERE rn >= 5
ORDER BY rn DESC;
The latter query runs fine in Postgres.
2 possible solutions here
Firstly using user variables to add a sequence number. Do this twice, and join the second set to the first where the sequence number is between the id - 1 and the id - 5. Then just use AVG. No correlated sub queries.
SELECT Sub3.id, Sub3.itemid, Sub3.deposit, AVG(Sub4.deposit)
FROM
(
SELECT Sub1.id, Sub1.itemid, Sub1.deposit, #Seq:=#Seq+1 AS Sequence
FROM
(
SELECT id, itemid, deposit
FROM products
ORDER BY id DESC
) Sub1
CROSS JOIN
(
SELECT #Seq:=0
) Sub2
) Sub3
LEFT OUTER JOIN
(
SELECT Sub1.id, Sub1.itemid, Sub1.deposit, #Seq1:=#Seq1+1 AS Sequence
FROM
(
SELECT id, itemid, deposit
FROM products
ORDER BY id DESC
) Sub1
CROSS JOIN
(
SELECT #Seq1:=0
) Sub2
) Sub4
ON Sub4.Sequence BETWEEN Sub3.Sequence + 1 AND Sub3.Sequence + 5
GROUP BY Sub3.id, Sub3.itemid, Sub3.deposit
ORDER BY Sub3.id DESC
Second one is cruder, and uses a correlated sub query (which is likely to perform poorly as the amount of data increases). Does a normal select but for the last column it has a sub query that refers to the id in the main select.
SELECT id, itemid, deposit, (SELECT AVG(P2.deposit) FROM products P2 WHERE P2.id BETWEEN P1.id - 5 AND p1.id - 1 ORDER BY id DESC LIMIT 5)
FROM products P1
ORDER BY id DESC
Is this what you are after?
SELECT m.id
, AVG(d.deposit)
FROM products m
, products d
WHERE d.id < m.id
AND d.id >= m.id - 5
GROUP BY m.id
ORDER BY m.id DESC
;
But can't be that simple. Firstly, the table cannot just contain one itemid (hence your WHERE clause); Second, the id cannot be sequential/without gaps within an itemid. Thirdly, you probably want to produce something that runs across itemid and not one itemid at a time. So here it is.
SELECT itemid
, m_id as id
, AVG(d.deposit) as deposit
FROM (
SELECT itemid
, m_id
, d_id
, d.deposit
, #seq := (CASE WHEN m_id = d_id THEN 0 ELSE #seq + 1 END) seq
FROM (
SELECT m.itemid
, m.id m_id
, d.id d_id
, d.deposit
FROM products m
, products d
WHERE m.itemid = d.itemid
AND d.id <= m.id
ORDER BY m.id DESC
, d.id DESC) d
, (SELECT #seq := 0) s
) d
WHERE seq BETWEEN 1 AND 5
GROUP BY itemid
, m_id
ORDER BY itemid
, m_id DESC
;