How would I do the following query in django:
Asset.objects.all().distinct('checksum') # get all distinct checksum items
The equivalent in SQL would be:
SELECT * FROM asset GROUP BY checksum
Note that I need all fields here, so I cannot do something like Asset.objects.values_list('checksum').distinct(). How would I do this?
Do you want to get the first item of every checksum?
items = Asset.objects.all()
items.query.group_by = ['checksum']
print items
[<Asset: ...]
Related
I tried to make a query to my database with this structure: Data Base Structure
I did this query:
SELECT partido.acronimoPartido, SUM(votosacta.numVotos) FROM partido, votosacta WHERE votosacta.partido_idpartido=1 AND partido.idpartido=1
This query does work like I want but displays only the SUM of 'votos' for idpartido=1
I want to be able to sum numVotos from 'votosacta' table for each member of my 'partido' table indexed in 'votosacta' but I seem to not be able to get the right sintax.
I tried something like this:
SELECT partido.acronimoPartido, SUM(votosacta.numVotos) FROM partido, votosacta WHERE votosacta.partido_idpartido = partido.idpartido
You need a group by clause:
select p.acronimoPartido,
SUM(v.numVotos)
from partido p
join votosacta v on v.partido_idpartido = p.idpartido
group by p.acronimoPartido
Also, use explicit join syntax instead of old comma based syntax and use aliases to make your queries concise and readable.
I can get the SELECT id from parts where name='Part1' as an SQL statement but what is the way to do that with SQLAlchemy?
I've tried;
db.session.query(Parts.id).filter(name=form.name.data)
But this returns an Object not the id
Use the below code.
parts = db.session.query(Parts).filter(Parts.name==Part1).first()
Then if you want the only id you can just access
parts.id
Store that object in a varaible, and then use dot notation to pull out what you want. For example:
item = db.session.query(Parts.id).filter(name=form.name.data).one()
print item.id
I have a piece of code which fetches the list of ids of users I follow.
#followed = current_user.followed_user_ids
It gives me a result like this [11,3,24,42]
I need to add these to NOT IN mysql query.
Currently, I am getting NOT IN ([11,3,24,42]) which is throwing an error. I need NOT IN (11,3,24,42)
This is a part of a find_by_sql statement, so using where.not is not possible for me in this point.
In rails 4:
#followed = current_user.followed_user_ids # #followed = [11,3,24,42]
#not_followed = User.where.not(id: #followed)
This should generate something like select * from users where id not in (11,3,24,42)
As you comment, you are using find_by_slq (and that is available in all rails versions). Then you could use the join method:
query = "select * from users where id not in (#{#followed.join(',')})"
This would raise mysql errors if #followed is blank, the resulting query would be
select * from users where id not in ()
To solve this whiout specifiying aditional if statements to your code, you can use:
query = "select * from users where id not in (0#{#followed.join(',')})"
Your normal queries would be like:
select * from users where id not in (01,2,3,4)
but if the array is blank then would result in
select * from users where id not in (0)
which is a still valid sql statement and is delivering no results (which might be the expected situation in your scenario).
you can do something like:
#followed = [11,3,24,42]
User.where('id not in (?)', #followed)
[major edit to make things clear]
I want to write a query that returns a dynamic column name like this:
SELECT
f2 AS
(
SELECT column_name
FROM column_names_tbl
WHERE column_name = "experience"
limit 0,1
)
FROM some_table
so that would output the same as this:
SELECT
f2 AS experience
FROM some_table
This is no correct SQL syntax, even because the two queries (the selected field and it's alias) are both subqueries and unrelated to each other. So, there's also no possibility for mysql to distinguish what name you want to connect to what value, even if the syntax was correct...
You already use a more or less normalized relational table, so I suggest the following solution:
you select the revision ID and name in a separate query; store them in PHP and use them for whatever you want
next, you evaluate the following query into a separated result set: SELECT ps.keyname, psv.keyvalue FROM page_setting_values AS psv INNER JOIN page_settings AS ps ON ps.id = psv.setting_id WHERE psv.page_revision_id = :revision with :revision representing your revision id
you may now assemble an associated array from that result set:
$settings = [];
$result = $db->executeQuery('...')->fetchAll();
foreach($result as $setting)
{
$settings[$setting['keyname']] = $setting['keyvalue'];
}
Hope that helps ;)
MySQL Server Version: Server version: 4.1.14
MySQL client version: 3.23.49
Tables under discussion: ads_list and ads_cate.
Table Relationship: ads_cate has many ads_list.
Keyed by: ads_cate.id = ads_list.Category.
I am not sure what is going on here, but I am trying to use COUNT() in a simple agreggate query, and I get blank output.
Here is a simple example, this returns expected results:
$queryCats = "SELECT id, cateName FROM ads_cate ORDER BY cateName";
But if I modify it to add the COUNT() and the other query data I get no array return w/ print_r() (no results)?
$queryCats = "SELECT ads_cate.cateName, ads_list.COUNT(ads_cate.id),
FROM ads_cate INNER JOIN ads_list
ON ads_cate.id = ads_list.category
GROUP BY cateName ORDER BY cateName";
Ultimately, I am trying to get a count of ad_list items in each category.
Is there a MySQL version conflict on what I am trying to do here?
NOTE: I spent some time breaking this down, item by item and the COUNT() seems to cause the array() to disappear. And the the JOIN seemed to do the same thing... It does not help I am developing this on a Yahoo server with no access to the php or mysql error settings.
I think your COUNT syntax is wrong. It should be:
COUNT(ads_cate.id)
or
COUNT(ads_list.id)
depending on what you are counting.
Count is an aggregate. means ever return result set at least one
here you be try count ads_list.id not null but that wrong. how say Myke Count(ads_cate.id) or Count(ads_list.id) is better approach
you have inner join ads_cate.id = ads_list.category so Count(ads_cate.id) or COUNT(ads_list.id) is not necessary just count(*)
now if you dont want null add having
only match
SELECT ads_cate.cateName, COUNT(*),
FROM ads_cate INNER JOIN ads_list
ON ads_cate.id = ads_list.category
GROUP BY cateName
having not count(*) is null
ORDER BY cateName
all
SELECT ads_cate.cateName, IFNULL(COUNT(*),0),
FROM ads_cate LEFT JOIN ads_list
ON ads_cate.id = ads_list.category
GROUP BY cateName
ORDER BY cateName
Did you try:
$queryCats = "SELECT ads_cate.cateName, COUNT(ads_cate.id)
FROM ads_cate
JOIN ads_list ON ads_cate.id = ads_list.category
GROUP BY ads_cate.cateName";
I am guessing that you need the category to be in the list, in that case the query here should work. Try it without the ORDER BY first.
You were probably getting errors. Check your server logs.
Also, see what happens when you try this:
SELECT COUNT(*), category
FROM ads_list
GROUP BY category
Your array is empty or disappear because your query has errors:
there should be no comma before the FROM
the "ads_list." prefix before COUNT is incorrect
Please try running that query directly in MySQL and you'll see the errors. Or try echoing the output using mysql_error().
Now, some other points related to your query:
there is no need to do ORDER BY because GROUP BY by default sorts on the grouped column
you are doing a count on the wrong column that will always give you 1
Perhaps you are trying to retrieve the count of ads_list per ads_cate? This might be your query then:
SELECT `ads_cate`.`cateName`, COUNT(`ads_list`.`category`) `cnt_ads_list`
FROM `ads_cate`
INNER JOIN `ads_list` ON `ads_cate`.`id` = `ads_list`.`category`
GROUP BY `cateName`;
Hope it helps?