I am trying to select the names from one table column and then ignore if any rows have the same member as the user id in a different column.
for example i would like to select all the "groupNames" from groups then check the "members" column for any members that match the user.
members groupName
mike test
andy test
eric runners
erica test
If the user was "mike", I would like the list to ignore any row that had the "groupName" test as "mike" also has that as a group name and the list should only display runners.
Is this possible? I have tried to research it but not even sure what I need to search for?
Does this do what you want?
select t.*
from groups t
where t.groupName <> (select t2.groupName from groups t2 where t2.members = 'Mike');
Related
I have two tables:
employees:
id, CMS_user_id, practice_group_id, ...
and
users:
id, level, ...
I want to select all employees where practice_group_id is 2 but only if the respective user has a level of 1 according to the users table. I researched and I have a feeling it has something to do with the UNION keyword eventually, but I can't quite figure it out.
In "human language", the query would be like this:
"select all from employees where practice_group_id is 2 and then check the CMS_user_id from the employee and check in the table users whether the respective user with the id that equals CMS_user_id has a level of 1"
A JOIN will match the corresponding rows between two tables. Then, filtering can be done using WHERE.
For example:
select e.*
from employees e
join users u on u.id = e.CMS_user_id
where e.practice_group = 2 and u.level = 1
I have two tables:
access(name, id, check, key)
events(name, key, event_name)
I am trying to print some things from these tables into a php/html table with these columns:
name, key, event_name, access count
My trouble being I would like each event to display the "count" of access rows that have the same key.
Event table example:
name key event_name
test 1 first
joe 2 second
And the access table...
name id check key
test 123 yes 1
test 1235 yes 1
joe 175 yes 2
joe 852 yes 2
test 5843 yes 1
test 123455 yes 1
The resulting table I am hoping to look like this:
name key event_name access count
test 1 first 4
joe 2 second 2
Does anybody know how to do this? I've gotten to this but it obviously doesn't work because the key isn't given to the inner select query...
select event_name, name, key,
(SELECT COUNT(key) FROM access WHERE key=key AND name=name)
from event;
Thank you to anyone who takes a look and might have any ideas! I've been staring at this and w3schools for hours
At present your subquery will return a count of all rows as it is not correlated to the main query, so both occurrences of key in key=key will refer to the same column and the expression will always be true (likewise for name). To correlate the subquery, add table references:
select event_name, name, key,
(SELECT COUNT(key) FROM access a WHERE a.key=e.key AND a.name=e.name) AS `access count`
from event e
You can also get the same results with a join and aggregattion:
select e.name, e.key, e.event_name, count(*) access_count
from event e
left join access a on a.key = e.key and a.name = e.name
group by e.name, e.key, e.event_name
I want to combine two tables.
table A: has multiple posts with unique URL and table B has votes for specific posts from table A.
Now I want to list all rows from table A and if a post has a vote in table B to attach that to one row.
I've tried this, but it excludes the posts who matches the table A with table B. It returns only without any votes.
SELECT a.id,a.url,a.content,a.sourcetype,a.width,a.height,a.totalvotes,a.score, b.postid,b.userid,b.votetype
FROM create_general a
LEFT JOIN votes b ON a.url=b.postid
WHERE a.status='1' and a.score > 0 order by a.url desc
LIMIT 24
Perhaps it would be nice to know more about the table structure, but you definitely do something wired in your on clause:
ON a.url=b.postid
This says, that the "url" in "table a" has to be the same than the "postid" in "table b".
Usually a url would look like this: "https://google.de" and a postid is just a number, perhaps "7", so they cannot be the same.
How would I write a query that would select the name of a person (a column in the row) given that they have enough rows to meet all conditions?
For example, I have a database set up like so:
name permission_id
Bob 1
Bob 2
Jerry 3
Jerry 1
Jose 2
Billy 1
Billy 2
How would I only select the people that have permission id 1 and 2? In other words, I would like a query that checks every person by name to see if they have all the permissions requested.
In this example if I was to check for all users to who have permission 1 and 2 I should get Bob and Billy as a return value.
Here is my current query:
$this->db->select('center_user_permissions.id, center_users.first_name, center_users.last_name');
$this->db->from('center_user_permissions');
$this->db->where_in('permission_id', $permission_ids);
$this->db->join('center_users', 'center_users.center_id = center_user_permissions.center_id');
Currently this query returns anybody who has either permission id 1 or 2. I need it to be 1 AND 2. But I know I can't simply make two wheres because one particular row can't have both permission ids, but the query must check all rows for the specified ids.
I believe I would need a SELECT statement inside of my where? Can anybody tell me if I'm thinking correctly? Thanks.
You can use a in clause an an having for check that the user has both the permission
select name
from center_user_permissions
where permissions_id in (1,2)
group by name
having count(*) = 2
I'm not sure how to build this query in CodeIgniter, but you could INNER JOIN for each permission ID you want the user to have:
SELECT center_users.center_id, center_users.first_name, center_users.last_name
FROM center_users
INNER JOIN center_user_permissions AS p1 ON p1.center_id=center_users.center_id AND p1.permission_id=1
INNER JOIN center_user_permissions AS p2 ON p2.center_id=center_users.center_id AND p2.permission_id=2
You could check for more permissions by adding a INNER JOIN for each additional permission you wanted to require.
MySQL's GROUP BY and HAVING
Not user what kind of DB interface you're using in $this->db, but it may make things a little tricky. If I start with a raw SQL query:
SELECT
center_user_permissions.id,
center_users.first_name,
center_users.last_name
FROM center_user_permissions
LEFT JOIN center_users
ON center_users.center_id = center_user_permissions.center_id
WHERE center_user_permissions.permission_id in (1,2)
Group by name, where count of permission_id is > 1
This will group rows by first_name (so you'll only get one row for each unique name). Doing do allows you to run aggregate functions (SUM(), MAX(), COUNT()) against the rows that were "grouped" into a single row.
SELECT
center_user_permissions.id,
center_users.first_name,
center_users.last_name
FROM center_user_permissions
LEFT JOIN center_users
ON center_users.center_id = center_user_permissions.center_id
GROUP BY center_users.first_name
WHERE center_user_permissions.permission_id in (1,2)
HAVING COUNT(center_user_permissions.permission_id)>1
select distinct(name),.. as name from 'center_user_permissions',center_users where
center_users.center_id = center_user_permissions.center_id and permissions_id in (1,2)
substitute .. with your other fields and put in distinct the value that you want to be unique
I'm having a small problem making a query in MySQL.
I have the following tables:
member;
group;
member_has_group (this one has the columns id_group referes to the group id and id_member referes to member id)
I'm trying to make a query that gives me the members from a selected group. Can you help me?
I'm not familiar with join tables, but for the search i made i think thats probably one of the solutions.
Thanks in advance.
Elkas
If you know the group id
select member.* from member m
inner join member_has_group mg on m.id = mg.id_member
where mg.id_group = [x]
If you only know the group name
select member.* from member m
inner join member_has_group mg on m.id = mg.id_member
inner join group g on g.id = mg.id_group
where g.name = 'group name'
This is trival in SQL :
SELECT m.id_member, m.name
FROM member AS m
INNER JOIN member_has_group AS h ON (m.id_member=h.id_member)
WHERE (h.id_group=#my_id_group)
#my_id_group is the group id you have to give.
Yep, you need a join here.
SELECT *
FROM `member`
JOIN `group` ON member.id = group.id
JOIN `member_has_group` ON group.id = member_has_group.id
Depending on the information in your tables, you may not need the third table at all.You only need a connector table with you have a "many to many" relationship between then.
(Ignore the rest if you already know
about database normalization)
For example, if you had two tables, Authors and Books. Authors would contain fields such as Name, Publisher, Birthday, whatever is a property of the "author". Books would contain relevant "book" information. This is a "one-to-many" relationship. An author may be linked (via a field such as author_id) to several books, but a book can only have one author. You would not need a third table here.
Building on that, say you had a third table for "Character Names". This would be a list of main character names used in any of the books in the "Books" table. One of the characters happens to be named John Steele. John has a whole series of books written about him. In the Books table, several of the books may list John Steele as a character. While in the characters table, John Steele could be listed in several books. This is "many-to-many". You need a third table here. It would only have two fields. A book_id and character_id, one entry for each book that John Steele appears in.
MySql Manual on DB Normalization