I'm going to implement a method on my own SQL. I have two tables in MySQL. Suppose that each row is updated in the FirstTable and the values of the rate and countView are variable, I'm trying to update them with the same command:
UPDATE FirstTable SET `countView`= `countView`+1,
`rate`=('$MyRate' + (`countView`-1)*`rate`)/`countView`
WHERE `productId`='$productId'
FirstTable:
productId | countView | rate | other column |
------------+-----------+------+-------------------+---
21 | 12 | 4 | anything |
------------+-----------+------+-------------------+---
22 | 18 | 3 | anything |
------------+-----------+------+-------------------+---
But in this way, a user can vote every time he wants to. So I tried to create a table with two columns productId and userID. Like below:
SecondTable:
productId | userID |
------------+---------------|
21 | 100001 |
------------+---------------|
22 | 100002 |
------------+---------------|
21 | 100001 |
------------+---------------|
21 | 100003 |
------------+---------------|
Now, as in the example given in the SecondTable, a user has given to a productId two vote. So I don't want both of these votes to be recorded.
Problems with this method:
The value of the counter is added to each vote.
I can not properly link the SecondTable and FirstTable to manage the update of the FirstTable.
Of course, this question may not be completely new, but I searched a lot to get the right answer. One of the questions from this site came through this method. Using this method, you can manage the update of a table. This method is as follows:
UPDATE `FirstTable` SET `countView`= `countView`+1,
`rate`=('$MyRate' + (`countView`-1)*`rate`)/`countView`
WHERE `productId`='$productId' IN ( SELECT DISTINCT productId, userID
FROM SecondTable)
But the next problem is that even when I use this command, I encounter the following error:
1241 - Operand should contain 1 column(s)
So thank you so much if you can guide me. And I'm sure my question is not duplicate... thank you again.
This fixes your specific syntax problem:
UPDATE FirstTable
SET countView = countView + 1,
rate = ($MyRate + (countView - 1) * rate) / countView
WHERE productId = $productId AND
productId IN (SELECT t2.productId FROM SecondTable t2);
But if two different users vote on the same product, FirstTable will be updated only once. It is unclear if that is intentional behavior or not.
Note that SELECT DISTINCT is not needed in the subquery.
The error is being generated because you can't return 2 fields in an "in" statement. You'll want to use group by:
Try:
IN ( SELECT DISTINCT productId FROM rating group by product, UserID)
Here's documentation to look over for mysql group by if you want: https://dev.mysql.com/doc/refman/5.7/en/group-by-handling.html
Related
I have design an event where you register multiple fishes and I wanted a query to extract the top 3 heaviest fishes from different people. In case of tie, it should be decided by a third parameter: who registered it first. I've tested several ways I found here on stack overflow but none of them worked the way I needed.
My schema is the following:
id | playerid | playername | itemid | weight | date | received | isCurrent
Where:
id = PK, AUTO_INCREMENT - it's basically an index
playerid = the unique code of the person who registered the fish
playername = name of the person who registered the fish
itemid = the code of the fish
weight = the weight of the fish
date = pre-defined as CURRENT_TIMESTAMP, the exact time the fish was registered
received = pre-defined as 0, it really don't matter for this analysis
isCurrent = pre-defined as 1, basically every time this event runs it updates this field to 0, meaning the registers don't belong to the current version of the event.
Here you can see the data I'm testing with
my problem is: How to avoid counting the same playerid for this rank more than once?
Query 1:
SELECT `playerid`, `playername`, `itemid`, `weight`
FROM `event_fishing`
WHERE `isCurrent` = 1 AND `weight` IN (
SELECT * FROM
(SELECT MAX(`weight`) as `fishWeight`
FROM `event_fishing`
WHERE `isCurrent` = 1
GROUP BY `playerid`
LIMIT 3) as t)
ORDER BY `weight` DESC, `date` ASC
LIMIT 3
Query 2:
SELECT * FROM `event_fishing`
INNER JOIN
(SELECT playerid, MAX(`weight`) as `fishWeight`
FROM `event_fishing`
WHERE `isCurrent` = 1
GROUP BY `playerid`
LIMIT 3) as t
ON t.playerid = `event_fishing`.playerid AND t.fishWeight = `event_fishing`.weight
WHERE `isCurrent` = 1
ORDER BY weight DESC, date ASC
LIMIT 3
Keep in mind that I must return at least the fields: playerid, playername, itemid, weight, that the version of the event must be the actual (isCurrent = 1), one playerid per line with the heaviest weight he registered for this version of the event and the date is registered.
Expected output for the data I've sent:
id |playerid|playername|itemid|weight| date |received| isCurrent
7 | 3734 |Mago Xxx | 7963 | 1850 | 2018-07-26 00:17:41 | 0 | 1
14 | 228 |Night Wolf| 7963 | 1750 | 2018-07-26 19:45:49 | 0 | 1
8 | 3646 |Test Spell| 7159 | 1690 | 2018-07-26 01:16:51 | 0 | 1
Output I'm getting (with both queries):
playerid|playername|itemid|weight
3734 |Mago Xxx | 7963 | 1850
228 |Night Wolf| 7963 | 1750
228 |Night Wolf| 7963 | 1750
Thank you for the attention.
EDIT: I've followed How can I SELECT rows with MAX(Column value), DISTINCT by another column in SQL? since my query is very similar to the accepted answer, in the comments I've found something that at a first glance seem to have solved my problem but I've found a case where the accepted answer fail. Check http://sqlfiddle.com/#!9/72aeef/1
If you take a look at data you'll notice that the id 14 was the first input of 1750 and therefore should be second place, but the MAX(id) returns the last input of the same playerid and therefore give us a wrong result.
Despite the problems seems alike, mine has a greater complexity and therefore the queries that were suggested doesn't work
EDIT 2:
I've managed to solve my problem with the following query:
http://sqlfiddle.com/#!9/d711c7/6
But I'll leave this question open because of two things:
1- I don't know if there's a case where this query might fail
2- Despite we limit a lot the first query, I still think this can be more optimized, so I'll leave it open to any one that might know a better way to solve the issue.
Table structure and data (I know data in IP/domain fields might not make much sense, but this is for illustration purposes):
rec_id | account_id | product_id | ip | domain | some_data
----------------------------------------------------------------------------
1 | 1 | 1 | 192.168.1.1 | 127.0.0.1/test | abc
2 | 1 | 1 | 192.168.1.1 | 127.0.0.1/other | xyz
3 | 1 | 1 | 192.168.1.2 | 127.0.0.1/test | ooo
Table has unique index ip_domain combined from ip and domain fields (so records with identical values in both fields can't exist).
In each case I know values for account_id, product_id, ip, domain fields, and I need to get other rows that have the SAME account_id, product_id values and one (or both) of ip, domain values are DIFFERENT.
Example: I know that account_id=1, product_id=1, ip=192.168.1.1, domain=127.0.0.1/test (so it matches rec_id 1), I need to select records with IDs 2 and 3 (because record 2 has different domain and record 3 has different ip).
So, I used query:
SELECT * FROM table WHERE
account_id='1' AND product_id='1' AND ip!='192.168.1.1' AND domain!='127.0.0.1/test'
Of course, it returned 0 rows. Looked at mysql multiple where and where not in and wrote:
SELECT * FROM table WHERE
account_id='1' AND product_id='1' AND installation_ip NOT IN ('192.168.1.1') AND installation_domain NOT IN ('127.0.0.1/test')
My guess is that this query is identical (just formatted different way), so 0 rows again. Found some more examples too, but none worked in my case.
The syntax is correct, but you're using the wrong logical operation
SELECT *
FROM table
WHERE account_id='1' AND product_id='1' AND
(ip != '192.168.1.1' OR domain != '127.0.0.1/test')
Select * from table
Where ROWID <> myRowid
And account_id = '1'
And product_id = '1';
myRowid is the unique id given by your dbms to each record, in this case you need to retrieve it with your select statement and then pass it back when using this select. This will return all the rows with account_id = 1 and product_id = 1 except the one you have selected.
If your inputs are not defined/or if you want list then you may be look at Group By clause. Also, you may look at group_concat
Query would be something like:
SELECT ACCOUNT_ID, PRODUCT_ID, GROUP_CONCAT(DISTINCT IP||'|'||DOMAIN, ','), COUNT(1)
FROM TABLE
GROUP BY ACCOUNT_ID, PRODUCT_ID
P.S.: I dont have mysql installed hence the query syntax is not verified
I asked a similar question earlier today, but I've run into another issue that I need assistance with.
I have a logging system that scans a server and catalogs every user that's online at that given moment. Here is how my table looks like:
-----------------
| ab_logs |
-----------------
| id |
| scan_id |
| found_user |
-----------------
id is an autoincrementing primary key. Has no real value other than that.
scan_id is an integer that is incremented after each successful scan of all users. It so I can separate results from different scans.
found_user. Stores which user was found online during the scan.
The above will generate a table that could look like this:
id | scan_id | found_user
----------------------------
1 | 1 | Nick
2 | 2 | Nick
3 | 2 | John
4 | 3 | John
So on the first scan the system found only Nick online. On the 2nd it found both Nick and John. On the 3rd only John was still online.
My problem is that I want to get the total amount of unique users connected to the server at the time of each scan. In other words, I want the aggregate number of users that have connected at each scan. Think counter.
From the example above, the result I want from the sql is:
1
2
2
EDIT:
This is what I have tried so far, but it's wrong:
SELECT COUNT(DISTINCT(found_user)) FROM ab_logs WHERE DATE(timestamp) = CURDATE() GROUP BY scan_id
What I tried returns this:
1
2
1
The code below should give you the results you are looking for
select s.scan_id, count(*) from
(select distinct
t.scan_id
,t1.found_user
from
tblScans t
inner join tblScans t1 on t.scan_id >= t1.scan_id) s
group by
s.scan_id;
Here is sqlFiddle
It assumes the names are unique and includes current and every previous scans in the count
Try with group by clause:
SELECT scan_id, count(*)
FROM mytable
GROUP BY scan_id
I want to return all rows that have a certain value in a column and have more than 5 instances in which a number is that certain value. For example, I would like to return all rows of the condition in which if the value in the column M has the number 1 in it and there are 5 or more instances of M having the number 1 in it, then it will return all rows with that condition.
select *
from tab
where M = 1
group by id --ID is the primary key of the table
having count(M) > 5;
EDIT: Here is my table:
id | M | price
--------+-------------+-------
1 | | 100
2 | 1 | 50
3 | 1 | 30
4 | 2 | 20
5 | 2 | 10
6 | 3 | 20
7 | 1 | 1
8 | 1 | 1
9 | 1 | 1
10 | 1 | 1
11 | 1 | 1
Originally I just want to insert into a trigger so that if the number of M = 1's is greater than 5, then I want to create an exception. The query I asked for would be inserted into the trigger. END EDIT.
But my table is always empty. Can anyone help me out? Thanks!
Try this :
select *
from tab
where M in (select M from tab where M = 1 group by M having count(id) > 5);
SQL Fiddle Demo
please try
select *,count(M) from table where M=1 group by id having count(M)>5
Since you group on your PK (which seems a futile excercise), you are counting per ID, whicg will indeed always return 1.
As i explain after this code, this query is NOT good, it is NOT the answer, and i also explain WHY. Please do not expect this query to run correctly!
select *
from tab
where M = 1
group by M
having count(*) > 5;
Like this, you group on what you are counting, which makes a lot more sense. At the same time, this will have unexpected behaviour, as you are selecting all kinds of columns that are not in the group by or in any aggregate. I know mySQL is lenient on that, but I don;t even want to know what it will produce.
Try indeed a subquery along these lines:
select *
from tab
where M in
(SELECT M
from tab
group by M
having count(*) > 5)
I've built a SQLFiddle demo (i used 'Test' as table name out of habit) accomplishing this (I don't have a mySQL at hand now to test it).
-- Made up a structure for testing
CREATE TABLE Test (
id INT NOT NULL AUTO_INCREMENT,
PRIMARY KEY(id),
M int
);
SELECT id, M FROM tab
WHERE M IN (
SELECT M
FROM Test
WHERE M = 1
GROUP BY M
HAVING COUNT(M) > 5
)
The sub-query is a common "find the duplicates" kind of query, with the added condition of a specific value for the column M, also stating that there must be at least 5 dupes.
It will spit out a series of values of M which you can use to query the table against, ending with the rows you need.
You shouldn't use SELECT * , it's a bad practice in general: don't retrieve data you aren't actually using, and if you are using it then take the little time needed to type in a list of field, you'll likely see faster querying and on the other hand the code will be way more readable.
I don't have any idea how to do this..
I have a table like this:
account_categories
--------------------
id | description
--------------------
34 | Home Services
35 | Home Services
36 | Home Services
39 | Home Design
40 | Home Design
I have another table (accounts) that references account_categories.id and it uses all of the above values. :/
I want to flatten account_categories, so I need to pick one duplicate from account_categories and update accounts so that all duplicates use the one selected value.
For instance, I need to turn this:
accounts
---------------------
id | accountCategory
---------------------
1 | 34
2 | 35
3 | 36
4 | 39
5 | 40
Into this:
accounts
---------------------
id | accountCategory
---------------------
1 | 34
2 | 34
3 | 34
4 | 39
5 | 39
I can select an id and distinct description from account categories like this:
SELECT DISTINCT (description), id
FROM crmalpha.account_categories
GROUP BY description
But I guess that the next step is to do something like this:
for ( row in ( SELECT DISTINCT (description), id FROM crmalpha.account_categories GROUP BY description ) ) {
UPDATE crmalpha.accounts SET accountCategory = $row['id'] WHERE accountCategory IN ( SELECT id FROM crmalpha.account_categories WHERE description = $row['description] )
}
Forgive the for loop and php variable pseudo code, I'm just trying to think through it logically. I have no idea how to accomplish this in pure SQL.
Any ideas?
PS., Afterwards, I will go through and delete from account_categories every row where the ID is not used in the accounts table.
This worked when I tried it against the test data you posted above. That said, when doing any mass cleanup like this I'd recommend making a copy of the table first. Also check results after issuing the UPDATE and before issuing a COMMIT.
Here's the query:
UPDATE Accounts acct
INNER JOIN Account_Categories cat ON acct.AccountCategory = cat.id
INNER JOIN (
SELECT MIN(id) AS NewID, Description
FROM Account_Categories
GROUP BY Description) NewCat ON cat.Description = NewCat.Description
SET acct.AccountCategory = NewCat.NewID
Some explanation:
The subquery (SELECT MIN(id)...) gets a single ID value (the lowest one) for each description.
The first join (to Account_Categories) associates each account with its category for the sole purpose of having the decription available.
The second join (to the subquery) associates the account's existing description to the table of flattened/de-duped descriptions and their ID.