This is how my MySQL table looks like :
Here, faculty_id and research_area are the primary keys. I want faculties who work in both “AI” and “Big Data”. So Ravi(F1) and Dham(F3) should be printed.
I tried select * from faculty_details where research_area='AI' AND research_area='Big Data'; and select * from faculty_details where research_area='AI' or research_area='Big Data'; but they didn't work.
One method uses group by and having:
select fd.faculty_id
from faculty_details fd
where fd.research_area in ('AI', 'Big Data')
group by fd.faculty_id
having count(*) = 2;
If you can have duplicates, then use:
having count(distinct research_area) = 2
Related
I have this query in sqlite:
SELECT
'L_MEDIA_ARTIST'.'MEDIA_ID'
FROM \
'L_MEDIA_ARTIST',
'L_ARTIST_CAT',
'ARTIST_CAT'
WHERE
'L_ARTIST_CAT'.'ART_ID' == 'L_MEDIA_ARTIST'.'ART_ID'
AND
'L_ARTIST_CAT'.'ART_CAT_ID' == 'ARTIST_CAT'.'ID'
AND
('ARTIST_CAT'.'NAME' == 'SINGER' OR 'ARTIST_CAT'.'NAME' == 'ACTOR')
which just selects all the media id such that the artist has at least one of the tag 'SINGER' or 'ACTOR'.
How can I change this query in order to obtain the list of all media such that the actor has neither the tag 'SINGER' nor the tag 'ACTOR'?
The involved tables are built up has follows:
CREATE TABLE 'L_MEDIA_ARTIST' (
'MEDIA_ID' INTEGER,
'ART_ID' INTEGER,
FOREIGN KEY('MEDIA_ID') REFERENCES MEDIA('ID'),
FOREIGN KEY('ART_ID') REFERENCES ARTIST('ID'),
UNIQUE('MEDIA_ID', 'ART_ID'));
CREATE TABLE 'L_ARTIST_CAT' (
'ART_ID' INTEGER,
'ART_CAT_ID' INTEGER,
FOREIGN KEY('ART_ID') REFERENCES ARTIST('ID'),
FOREIGN KEY('ART_CAT_ID') REFERENCES ARTIST_CAT('ID'),
UNIQUE('ART_ID', 'ART_CAT_ID'));
CREATE TABLE 'ARTIST_CAT' (
'ID' INTEGER PRIMARY KEY,
'NAME' TEXT NOT NULL UNIQUE);
You need an aggregation query for this, because you have to check that none of the values for a media are in the list. Just looking on one row doesn't provide enough information:
SELECT l.MEDIA_ID
FROM L_MEDIA_ARTIST l JOIN
L_ARTIST_CAT ac
ON l.ART_ID = ac.ART_ID JOIN
ARTIST_CAT c
ON ac.ART_CAT_ID = c.ID
GROUP BY l.MEDIA_ID
HAVING SUM(CASE WHEN c.Name IN ('SINGER', 'ACTOR') THEN 1 ELSE 0 END) = 0;
Note that I also fixed the query:
Introduced proper join syntax. You should learn modern join syntax.
Added table aliases so the query is easier to write and to read.
Removed the single quotes around table and column names, which just cause syntax errors.
The HAVING clause counts the number of times that "SINGER" and "ACTOR" are found in the data. The = 0 ensures there are none for a given media.
The media IDs that you do not want can be retrieved with this query:
SELECT L_Media_Artist.Media_ID
FROM L_Media_Artist
JOIN L_Artist_Cat USING (Art_ID)
JOIN Artist_Cat ON L_Artist_Cat.Art_Cat_ID = Artist_Cat.ID
WHERE Artist_Cat.Name IN ('SINGER', 'ACTOR')
(This is the same as your first query.)
So you want all media that are not one of those:
SELECT ID
FROM Media
WHERE ID NOT IN (SELECT L_Media_Artist.Media_ID
FROM L_Media_Artist
JOIN L_Artist_Cat USING (Art_ID)
JOIN Artist_Cat ON L_Artist_Cat.Art_Cat_ID = Artist_Cat.ID
WHERE Artist_Cat.Name IN ('SINGER', 'ACTOR'))
I have a list of ids, and I want to query a mysql table for ids not present in the table.
e.g.
list_of_ids = [1,2,4]
mysql table
id
1
3
5
6
..
Query should return [2,4] because those are the ids not in the table
since we cant view ur code i can only work on asumption
Try this anyway
SELECT id FROM list_of_ids
WHERE id NOT IN (SELECT id
FROM table)
I hope this helps
There is a horrible text-based hack:
SELECT
substr(result,2,length(result)-2) AS notmatched
FROM (
SELECT
#set:=replace(#set,concat(',',id,','),',') AS result
FROM (
select #set:=concat(',',
'1,2,4' -- your list here
,',')
) AS setinit,
tablename --Your tablename here
) AS innerview
ORDER BY LENGTH(result)
LIMIT 1;
If you represent your ids as a derived table, then you can do this directly in SQL:
select list.val
from (select 1 as val union all
select 2 union all
select 4
) list left outer join
t
on t.id = list.val
where t.id is null;
SQL doesn't really have a "list" type, so your question is ambiguous. If you mean a comma separated string, then a text hack might work. If you mean a table, then something like this might work. If you are constructing the SQL statement, I would advise you to go down this route, because it should be more efficient.
I have a funky query that works fine with static data but I need my data to be dynamic. So the static data is like this
SELECT c.my_name, c.my_id, (SELECT count(d.friendship_id) FROM another_table d WHERE d.my_id = 1 AND d.my_friends_id = 2) as count FROM myprofile c WHERE c.my_id = 1;
This returns the data I want like this:
my_name my_id count
parijat 123 1 (OR 0 if the row doesn't exist)
For reference, both another_table.my_id (foreign key), another_table.my_friends_id references myprofile.my_id (primary key). another_table.friendship_id is the primary key here and is auto incremented.
Now the actual question:
I want my subquery to be something like this:
(SELECT count(d.friendship_id) FROM another_table d WHERE d.my_id = 1 AND d.my_friends_id = CURRENT_ROW_ID)
where CURRENT_ROW_MY_ID is the c.my_id that is being selected upon in the main query.
Is this possible and if not, what should my approach be to get the results I need ?
You can do a subquery to get the current auto_increment value for that table:
select auto_increment from information_schema.tables where table_schema = 'you_db_name' and table_name = 'your_table_name'
HTH
Francisco
Sometimes I ask before I have completely explored the option. Just found out that a correlated subquery works fine even in select statements. Here is what I did to get it working:
SELECT c.my_name, c.my_id, (SELECT count(d.friendship_id) FROM another_table d WHERE d.my_id = 1 AND d.my_friends_id = c.my_id) as count FROM myprofile c WHERE c.my_id = 1;
my_id is slightly ambiguous. A better word for it would be profile_id, however dealing with a legacy database ain't fun for sure.
I have a table with a composite key composed of 2 columns, say Name and ID. I have some service that gets me the keys (name, id combination) of the rows to keep, the rest i need to delete. If it was with only 1 row , I could use
delete from table_name where name not in (list_of_valid_names)
but how do I make the query so that I can say something like
name not in (valid_names) and id not in(valid_ids)
// this wont work since they separately dont identity a unique record or will it?
Use mysql's special "multiple value" in syntax:
delete from table_name
where (name, id) not in (select name, id from some_table where some_condition);
If your list is a literal list, you can still use this approach:
delete from table_name
where (name, id) not in (select 'john', 1 union select 'sally', 2);
Actually, no I retract my comment about needing special juice or being stuck with (AND OR'ing all your options).
Since you have a list of values of what you want to retain, dump that into a temporary table. Then do a delete against the base table for what does not exist in the temporary table (left outer join). I suck at mysql syntax or I'd cobble together your query. Psuedocode is approximate
DELETE
B
FROM
BASE B
LEFT OUTER JOIN
#RETAIN R
ON R.key1 = B.key1
AND R.key2 = B.key
WHERE
R.key1 IS NULL
The NOT EXISTS version:
DELETE
b
FROM
BaseTable b
WHERE
NOT EXISTS
( SELECT
*
FROM
RetainTable r
WHERE
(r.key1, r.key2) = (b.key1, b.key2)
)
I have a table like this (MySQL 5.0.x, MyISAM):
response{id, title, status, ...} (status: 1 new, 3 multi)
I would like to update the status from new (status=1) to multi (status=3) of all the responses if at least 20 have the same title.
I have this one, but it does not work :
UPDATE response SET status = 3 WHERE status = 1 AND title IN (
SELECT title FROM (
SELECT DISTINCT(r.title) FROM response r WHERE EXISTS (
SELECT 1 FROM response spam WHERE spam.title = r.title LIMIT 20, 1)
)
as u)
Please note:
I do the nested select to avoid the famous You can't specify target table 'response' for update in FROM clause
I cannot use GROUP BY for performance reasons. The query cost with a solution using LIMIT is way better (but it is less readable).
EDIT:
It is possible to do SELECT FROM an UPDATE target in MySQL. See solution here
The issue is on the data selected which is totaly wrong.
The only solution I found which works is with a GROUP BY:
UPDATE response SET status = 3
WHERE status = 1 AND title IN (SELECT title
FROM (SELECT title
FROM response
GROUP BY title
HAVING COUNT(1) >= 20)
as derived_response)
Thanks for your help! :)
MySQL doesn't like it when you try to UPDATE and SELECT from the same table in one query. It has to do with locking priorities, etc.
Here's how I would solve this problem:
SELECT CONCAT('UPDATE response SET status = 3 ',
'WHERE status = 1 AND title = ', QUOTE(title), ';') AS sql
FROM response
GROUP BY title
HAVING COUNT(*) >= 20;
This query produces a series of UPDATE statements, with the quoted titles that deserve to be updated embedded. Capture the result and run it as an SQL script.
I understand that GROUP BY in MySQL often incurs a temporary table, and this can be costly. But is that a deal-breaker? How frequently do you need to run this query? Besides, any other solutions are likely to require a temporary table too.
I can think of one way to solve this problem without using GROUP BY:
CREATE TEMPORARY TABLE titlecount (c INTEGER, title VARCHAR(100) PRIMARY KEY);
INSERT INTO titlecount (c, title)
SELECT 1, title FROM response
ON DUPLICATE KEY UPDATE c = c+1;
UPDATE response JOIN titlecount USING (title)
SET response.status = 3
WHERE response.status = 1 AND titlecount.c >= 20;
But this also uses a temporary table, which is why you try to avoid using GROUP BY in the first place.
I would write something straightforward like below
UPDATE `response`, (
SELECT title, count(title) as count from `response`
WHERE status = 1
GROUP BY title
) AS tmp
SET response.status = 3
WHERE status = 1 AND response.title = tmp.title AND count >= 20;
Is using GROUP BY really that slow ? The solution you tried to implement looks like requesting again and again on the same table and should be way slower than using GROUP BY if it worked.
This is a funny peculiarity with MySQL - I can't think of a way to do it in a single statement (GROUP BY or no GROUP BY).
You could select the appropriate response rows into a temporary table first then do the update by selecting from that temp table.
you'll have to use a temporary table:
create temporary table r_update (title varchar(10));
insert r_update
select title
from response
group
by title
having count(*) < 20;
update response r
left outer
join r_update ru
on ru.title = r.title
set status = case when ru.title is null then 3 else 1;