situation:
table 1 - #__virtuemart_products
virtuemart_product_id | product_special
PRODUCTS_IDS | 0 or 1
table 2 - #__virtuemart_product_badges
virtuemart_product_id | product_badge
PRODUCTS_IDS | for this situation code 3
I have a default SQL
SELECT p.`virtuemart_product_id`
FROM `#__virtuemart_products` as p
WHERE p.`product_special` = 1;
results is product IDs like 2,3,225,...
I need modify this SQL syntax for select IDs from 2 different tables and return one column.
If I modify syntax like that:
SELECT p.`virtuemart_product_id`, badges_table.`virtuemart_product_id`
FROM `#__virtuemart_products` as p, `#__virtuemart_product_badges` as badges_table
WHERE p.`product_special` = 1 OR badges_table.`badge` = 3
Result is:
virtuemart_product_id | virtuemart_product_id
1 | 123
1 | 321
1 | 231
....
why is first column 1,1,1,...? here must be product_id, no product_special code
I need group this results into one column virtuemart_product_id
What I doing wrong?
I think what you are looking for is UNION of the IDs fetched from two different tables.
SELECT p.`virtuemart_product_id`, badges_table.`virtuemart_product_id`
FROM `#__virtuemart_products` as p, `#__virtuemart_product_badges` as
badges_table
WHERE p.`product_special` = 1 OR badges_table.`badge` = 3
What the above query is doing is, it is performing a join between the two tables with the condition that product_special should be 1 or badge should be 3. Hence, each row from one table will be joined with each row of the other table where the condition will satisfy.
To get IDs from both the tables you can get the results from each table according to condition and then perform a UNION on them. So for example
(SELECT `virtuemart_product_id` FROM `#__virtuemart_products` WHERE
`product_special` = 1)
UNION
(SELECT `virtuemart_product_id` FROM
`#__virtuemart_product_badges` WHERE `badge` = 3)
I hope this helps.
i have a table like this on a mysql database:
id | item
-----------
1 | 2
2 | 2
3 | 4
4 | 5
5 | 8
6 | 8
7 | 8
i want the result to be 3 record with the highest Item value
select max(item) returns only 1 value
how can i select multiple max values?
thank you
You can use a derived table to get the maximum value and join it back to the original table to see all rows corresponding to it.
select t.id, t.item
from tablename t
join (select max(item) as mxitem from tablename) x
on x.mxitem = t.item
Edit:
select t.co_travelers_id, t.booking_id, t.accounts_id
from a_co_travelers t
join (select accounts_id, max(booking_id) as mxitem
from a_co_travelers
group by accounts_id) x
on x.mxitem = t.booking_id and t.accounts_id = x.accounts_id
If you use an 'aggregate function' without GROUP BY only one row will be returned.
You may use GROUP BY , with aggregate functions.
Here is SQLFiddle Demo
SELECT id,max(item) AS item
FROM table_name
GROUP BY id
ORDER BY item DESC
LIMIT 3
Hope this helps.
There is the graphical explanation.
There is script mysql (low abstraction level, no inner join or sth)
select * from ocena, uczen where ocena.ocena = (SELECT MAX(ocena.ocena) FROM ocena WHERE ocena.przedmiot_id="4" and ocena.uczen_id="1") and ocena.uczen_id=uczen.id and ocena.przedmiot_id="4" and uczen_id="1"
This table lists user and item id's
user_id item_id
1 1
1 2
1 3
2 1
2 3
3 1
3 4
3 3
How can I run a query on this table to list all the items that are common between given users.
My guess is, this will need a self join, but I'm not sure.
i am trying this quering but it's returning an error
SELECT *
FROM recs 1
JOIN recs 2 ON 2.user_id='2' AND 2.item_id=1.item_id
WHERE 1.user_id='1'
Try using alias names that start in a letter:
SELECT *
FROM recs r1
JOIN recs r2 ON r2.user_id='2' AND r2.item_id=r1.item_id
WHERE r1.user_id='1'
This returns
user_id item_id
------- -------
1 1
1 3
for your data. Demo on sqlfiddle.
Note: I kept single quotes in the query, because I assume that both IDs in your table are of character type. If that is not the case, remove single quotes around user ID values '1' and '2'.
I want it for n number of users ... a I want the query to return all item_id's that are common among the users
SELECT DISTINCT(r1.item_id)
FROM recs r1
WHERE EXISTS (
SELECT *
FROM recs r2
WHERE r2.item_id=r1.item_id
AND r1.user_id <> r2.user_id
)
Demo #2.
I have the following MySQL table:
id rid
----- ------
1 2
2 1
2 3
3 2
1 3
3 1
I want to change this so only one row per relation exists.
e.g:
id rid
----- ------
1 2
2 3
1 3
If you always have pairs (as in your example):
delete from table
where id > rid;
This keeps the record where id is smaller.
If there is the possibility that no all pairs exist, then:
delete t
from table t left outer join
(select least(id, rid) as lid, greatest(id, rid) as gid, count(*) as cnt
from table t2
group by least(id, rid), greatest(id, rid)
) t2
on least(t.id, t.rid) = t2.lid and greatest(t.id, t.rid) = gid
where id < rid or t2.cnt = 1;
EDIT (explanation):
How does the second query work? Let me be honest, what I want to write is this:
delete t from table t
where id < rid or
(id > rid and
not exists (select 1 from table t2 where t2.id = t.rid and t2.rid = t.id
);
That is, I want to keep all records where id < rid. But then, I also want to keep all singleton records where rid > id. I don't think MySQL allows the syntax with the where clause.
Instead, the query in the answer counts the number of times that a pair exists, by looking at the smallest value and the largest value. For the data in the question, the result of the subquery is:
id rid cnt
1 2 2
2 3 2
1 3 2
So, all of these would use the id < rid to select the row. If you had one more row, say 4, 1. It would look like:
lid gid cnt
1 2 2
2 3 2
1 3 2
1 4 1
In this case, the first three would take the row with id < rid. But the new row would also be selected because the cnt is 1.
If you had duplicates in the table and a primary key, there would be a slight variation on the query that would do the same thing.
UPDATED
id | id_list
1 | 2,3,5,7
2 | 1,4,5,6
3 | 1,4,6,7
4 | 2,3,5,8
5 | 1,2,4,8
6 | 2,3,7,8
7 | 1,3,6,9
8 | 4,5,6,9
9 | 7,8
let's say I'm up to the content of id=1
I wanted to select all the rows where id is in id_list of id=1 PLUS the row where id=1
so the result would be
rows with id = 1,2,3,5,7
How to do this query guys?
You can also use a self join
Using IN()
select * from atable a
join atable b on (a.id = b.id )
where 1 IN (a.id_list) or b.id =1
Fiddle with IN()
Using FIND_IN_SET()
select * from atable a
join atable b on (a.id = b.id )
where FIND_IN_SET('1', a.id_list) or b.id =1
Fiddle with FIND_IN_SET()
Using UNION ALL
select * from atable
where id =1
UNION ALL
select * from atable
where 1 IN (id_list)
Fiddle with UNION ALL
Your database design is broken; id_list should be represented as a join table instead of as a string. However, to solve your immediate problem:
select * from table where id=1
or id_list like '1%'
or id_list like '%,1,%'
or id_list like '%,1'
Adjust as needed for PreparedStatement. You have to provide all three cases because if you just did
or id_list like '%1%'
and id_list contained the value 11, you'd get an incorrect match
Try this (see SQL-Fiddle):
SELECT * FROM tbl
WHERE id = 1
OR INSTR((SELECT id_list FROM tbl WHERE id = '1'), id) > 0;
Tested with MySQL 5.5.30
try this one
select *
from tbl
where id=1
or id_list like '%1%'
This appears to call for a union of two sets. The one set would be the single row whose id matches the specified value:
SELECT
id
FROM
atable
WHERE
id = #id
The other set would be the result of this self-join:
SELECT
item.id
FROM
atable AS item
INNER JOIN
atable AS list
ON
FIND_IN_SET(item.id, list.id_list)
WHERE
list.id = #id
That is, the row with the specified id is matched against every row in the table on the condition that the other row's id is found in the specified row's id_list.
You can try the complete query at SQL Fiddle.
Please note that lists aren't a very good design feature. In your situation, it might be better to use a many-to-many table as suggested by #Othman. Only I would probably use a slightly different query to get the desired output, because his doesn't include the specified row itself:
SELECT
id
FROM
manytomany
WHERE
id = #id
UNION
SELECT
linked_id
FROM
manytomany
WHERE
id = #id
;
While the entries in manytomany are assumed to be unique, the query uses the UNION DISTINCT operator because of the potential duplicates returned by the first subquery, although it is possible to move the application of DISTINCT to the first subquery only like this:
SELECT DISTINCT
id
FROM
manytomany
WHERE
id = #id
UNION ALL
SELECT
linked_id
FROM
manytomany
WHERE
id = #id
;
That first subquery could actually be rewritten simply as SELECT #id AS id, but the rewrite would only make sense if the passed value was guaranteed to be valid, i.e. that it would definitely be found in manytomany.id.
Here's a demo for the other approach too (all three variations, including the SELECT #id AS id one).
I don't have an answer for your question but I encourage you to redesign your table like this I think this called many to many relation
id | friend
1 | 2
1 | 3
1 | 5
1 | 7
2 | 1
2 | 4
2 | 5
2 | 6
3 | 1
3 | 4
3 | 6
3 | 7
And then your query will be like this
SELECT DISTINCT(friend) FROM `new` WHERE id = 1
I am assuming you are using php..
My suggestion is to grab the id_list for id 1.
Explode that id_list on the comma, and then do another mysql query to grab the remaining results for 5|3|6|8
ex) $idarray = explode(",", $result);
select * from your_table where id in ('5','3','6','8')
OPTION 2:
SELECT * FROM your_table
WHERE id = '1'
OR id IN ('\''+(SELECT REPLACE(id_list,',','\',\'') FROM your_table WHERE id = '1')+'\'')
EDIT: Oops, sorry, that should be an OR instead.