I have two tables, users and posts. I'm trying to write a single query that finds the latest post by a user, but I'm having trouble. Here's what I have so far.
select a.username, b.last_post from logins as a join (select login_id, entry as last_post from posts) as b where a.id = b.login_id
+-----------+---------------------+
| username | last_post |
+-----------+---------------------+
| something | 2013-10-08 22:12:00 |
| other | 2013-10-08 22:13:00 |
| test | 2013-10-08 22:13:03 |
| test | 2013-10-08 22:14:20 |
| hello | 2013-10-08 22:12:53 |
| hello | 2013-10-08 22:12:56 |
+-----------+----------+----------+
So right now last_post is simply the timestamp of the post it's pulling. How do I get a table that displays ONLY the last post from these users?
if you only need two column, you can directly use MAX()
SELECT a.username,
MAX(b.entry) last_post
FROM logins a
INNER JOIN posts b
ON a.id = b.login_id
GROUP BY a.username
otherwise, if you want to show all columns in all table, you can have subquery which separately gets the latest entry for every login_id
SELECT a.*, b.*
FROM logins a
INNER JOIN posts b
ON a.id = b.login_id
INNER JOIN
(
SELECT login_id, MAX(entry) entry
FROM posts
GROUP BY login_id
) c ON b.login_id = c.login_id AND
b.entry = c.entry
Related
I have 3 tables, users and tasks and completed_tasks. So basically I want to select all tasks where the user_id = 2 AND also check that the task does not exist in another table` the So here is my tables:
users table:
+----+-------+
| id | name |
+----+-------+
| 1 | John |
| 2 | Sally |
+----+-------+
tasks table:
+----+-----------+---------+
| id | task_name | user_id |
+----+-----------+---------+
| 1 | mop floor | 2 |
| 2 | dishes | 1 |
| 3 | laundry | 2 |
| 4 | cook | 2 |
+----+-----------+---------+
completed_tasks table:
+----+---------+---------+
| id | task_id | user_id |
+----+---------+---------+
| 1 | 1 | 2 |
+----+---------+---------+
Here is my current SELECT code for my MySQL database:
$db = "SELECT DISTINCT tasks.task_name, users.name FROM tasks LEFT JOIN ON users.id = tasks.user_id WHERE tasks.user_id = 2";
THe problem I'm having is: I want it to search in completed_tasks table and if the task exists, then don't select that task.
I tried to do that by adding the following but it did not work:
LEFT JOIN completed_tasks ON completed_tasks.user_id = 2
That did not work because if I had multiple completed tasks, it would just ignore it all together.
I want the end result should return the user's name and task name of task 3 and 4.
Also, performance is critical in my application. I could use PHP and loop through the arrays and do SELECT for each of them but that would not be good for performance.
You have a few ways to do this.
You can use a LEFT JOIN and then check for NULL in the optional table.
SELECT a.name, b.task_name
FROM users a
JOIN tasks b ON a.id = b.user_id
LEFT JOIN completed_tasks c ON c.task_id = b.id AND c.user_id = b.user_id
WHERE c.id IS NULL
;
You can do a NOT EXISTS sub-query
SELECT a.name, b.task_name
FROM users a
JOIN tasks b ON a.id = b.user_id
WHERE NOT EXISTS (
SELECT 1
FROM completed_tasks c
WHERE c.task_id = b.id AND c.user_id = b.user_id)
;
I'm struggling with mysql joins :/
I've multiple tables inside database fe. tasks, users etc.
Table tasks containing tasks with various variables, but the most important - id's of users signed to task (as different roles inside the task - author, graphic, corrector):
+---------+-------------+--------------+
| task_id | task_author | task_graphic |
+---------+-------------+--------------+
| 444 | 1 | 2 |
+---------+-------------+--------------+
Table users
+---------+----------------+------------+-----------+
| user_id | user_nice_name | user_login | user_role |
+---------+----------------+------------+-----------+
| 1 | Nice Name #1 | login1 | 0 |
+---------+----------------+------------+-----------+
| 2 | Bad Name #2 | login2 | 1 |
+---------+----------------+------------+-----------+
Using PDO I'm getting the whole data I want while using INNER JOIN with data from different tables (and $_GET variable)
SELECT tasks.*, types.types_name, warehouse.warehouse_id, warehouse.warehouse_code, warehouse.warehouse_description
FROM tasks
INNER JOIN types ON types.types_id = tasks.task_id
INNER JOIN warehouse ON warehouse.warehouse_id = tasks.task_id
WHERE tasks.task_id = '".$get_id."'
ORDER BY tasks.task_id
Above query returns:
+---------+--------------+--------------+----------------+------------+-----------+------------------+------------------------+------------+-------------+-----------------+-----------+----------------+--------------------+---------------------+-----------+---------------------+------------------+---------------------+
| task_id | task_creator | task_graphic | task_purchaser | task_title | task_lang | task_description | task_description_files | task_files | task_status | task_prod_index | task_type | task_print_run | task_print_company | task_warehouse_code | task_cost | task_time_added | task_deadline | task_date_warehouse |
+---------+--------------+--------------+----------------+------------+-----------+------------------+------------------------+------------+-------------+-----------------+-----------+----------------+--------------------+---------------------+-----------+---------------------+------------------+---------------------+
| 2 | 1 | 2 | 1 | Test | PL | Lorem ipsum (?) | | | w | 2222 | 3 | 456546 | Firma XYZ | 2 | 124 | 29.09.2016 15:48:20 | 01.10.2016 12:00 | 07.10.2016 14:00 |
+---------+--------------+--------------+----------------+------------+-----------+------------------+------------------------+------------+-------------+-----------------+-----------+----------------+--------------------+---------------------+-----------+---------------------+------------------+---------------------+
And I'd like to get query with added user_nice_name after task_creator, task_author and task_graphic - obviously nice names selected from table users based on ID's provide in 3 above fields fe.
+---------+--------------+------------------------------------+--------------+--------------------------------------+
| task_id | task_creator | task_creator_nn | task_graphic | task_graphic |
+---------+--------------+------------------------------------+--------------+--------------------------------------+
| 2 | 1 | Nice Name (from task_creator ID=1) | 2 | Nice Name (from task_graphic ID = 2) |
+---------+--------------+------------------------------------+--------------+--------------------------------------+
How can I achieve that?
You need three joins:
SELECT t.*,
uc.user_nice_name as creator_name,
ug.user_nice_name as graphic_name,
up.user_nice_name as purchaser_name,
ty.types_name, w.warehouse_id, w.warehouse_code, w.warehouse_description
FROM tasks t INNER JOIN
types ty
ON ty.types_id = t.task_id INNER JOIN
warehouse w
ON w.warehouse_id = t.task_id LEFT JOIN
users uc
ON uc.user_id = t.task_creator LEFT JOIN
users ug
ON ug.user_id = t.task_graphic LEFT JOIN
users up
ON up.user_id = t.task_purchaser
WHERE t.task_id = '".$get_id."'
ORDER BY t.task_id;
Notes:
Table aliases make the query easier to write and to read. They are also required because you have three references to users in the FROM clause.
This uses LEFT JOIN for the users in case some of the reference values are missing.
You need to work on your naming. It doesn't make sense that a "warehouse" id matches a "task" id. Or that a "task" id matches a "types" id. But that is how you phrased the query in your question.
The ORDER BY effectively does nothing, because all rows have the same task_id.
Assuming that the task_graphic_name is inside a table name task_graphic_table and the relation field are task_graphic_id
SELECT tasks.*
, types.types_name
, warehouse.warehouse_id
, warehouse.warehouse_code
, warehouse.warehouse_description
, users.user_nice_name
FROM tasks
INNER JOIN types ON types.types_id = tasks.task_id
INNER JOIN warehouse ON warehouse.warehouse_id = tasks.task_id
INNER JOIN users ON users.user_nice_name = tasks.task_graphic
WHERE tasks.task_id = '".$get_id."'
ORDER BY tasks.task_id
And if you need the column appear in a specific order you should explicitally call the column name in sequence eg:
SELECT tasks.col1
, task.col2
, types.types_name
, warehouse.warehouse_id
, warehouse.warehouse_code
, task.col2
, warehouse.warehouse_description
, task_graphic_table.task_graphic_name
Add two sub query in with your query. like
SELECT tasks.*,
....
....,
(select user_nice_name from users where id = tasks.task_author) AS task_creator_name,
(select user_nice_name from users where id = tasks.task_graphic) AS task_graphic_name
FROM tasks
INNER JOIN types ON types.types_id = tasks.task_id
....
....
I'm making a search function in PHP and I have three tables that I wish to join to a single one; the three tables looks as follow:
band
ID | bands
---+----------
1 | Muse
2 | Coldplay
3 | etc.
release
ID | releases
---+----------
1 | Showbiz
2 | Origin of Symmentry
3 | etc.
track
ID | tracks
---+-----------
1 | Sunburn
2 | Muscle Museum
3 | etc.
I want these tables to be put into this:
discografic
ID | band_id | release_id | track_id
---+----------+-------------+---------
1 | 1 | 1 | 1
2 | 1 | 1 | 2
3 | etc.
So that the table with the SQL code looks like this:
discografic
ID | bands | releases | tracks
---+----------+-------------+---------
1 | Muse | Showbiz | Sunburn
2 | Muse | Showbiz | Muscle Museum
3 | etc.
I want to INNER JOIN these tables. I joined one but I can't really figure out how the get the last joined as well.
SELECT *
FROM band
INNER JOIN discografic
ON band.id = discografic.band_id
This should probably have its own question; I also want to be able to search this database, but only have the result show up once, and also reference to the band every time. For example, if I search "Showbiz" it will give me "Muse", and only show it once.
Note: This is for testing purposes only, security is none of my concerns.
Try with this query:
select d.id,b.bands,r.releases,t.tracks from discografic as d INNER JOIN band as b on
d.band_id=b.id INNER JOIN release as r on d.release_id=r.id INNER JOIN track as t on
d.track_id=t.id GROUP BY d.id
Try This query
Select a.ID,b.bands,c.releases,d.tracks from discografic as a
inner join band as b on a.band_id = b.ID
inner join release as c on a.release_id = c.ID
inner join track as d on a.track_id = d.ID
where b.bands = 'Muse'
Use this query to insert the data like you wanted:
Insert into discograpy
(id,bands,releases,tracks)
SELECT band.ID,bands,releases,tracks
FROM band
INNER JOIN releases
ON band.id = releases.id
inner join track
on band.id = track.id
Use this query to show you only one band:
Declare #releases varchar(50)
Set #releases = 'showbiz'
SElect distinct bands from discograpy where releases = #releases
Here any variable can be passed or set in place of showbiz. This is an example
I'm having difficulty figuring out how to create the proper syntax for my query.
Here is what i'm pulling. I have 2 tables.
Table 1 : Fields (user_id, name)
Table 2 : Fields (user_id, type, are_code, phone_number).
Table 1 can only have 1 record per user_id.
1 | John Doe
Table 2 can have up to 3 records per user_id:
1 | Home | 123 | 456.4567
1 | Work | 000 | 987.1467
1 | Mobi | 098 | 987.1756
How can i select everything so that my table will result in 1 record pulled like so :
user_id | name | home# | work# | mobi#
I tried this, which duplicates and doubles rows based on amount of entries within Table 2.
SELECT a.user_id,
b.area_code, b.phone_number
FROM users a
INNER JOIN user_contact_phones b ON a.user_id = b.user_id
That unfortunately returned 3 rows which is not good :(.
1 | John Doe | area | home# |
1 | John Doe | area | work# |
1 | John Doe | area | mobi# |
Any help and or pointers would be greatly appreciated.
Try this out:
SELECT
u.user_id,
u.name,
MAX(CASE WHEN p.type = 'Home' THEN phone_number END) HomeNumber,
MAX(CASE WHEN p.type = 'Work' THEN phone_number END) WorkNumber,
MAX(CASE WHEN p.type = 'Mobi' THEN phone_number END) MobiNumber
FROM phones p
JOIN users u ON p.user_id = u.user_id
GROUP BY u.user_id, u.name
Output:
| USER_ID | NAME | HOMENUMBER | WORKNUMBER | MOBINUMBER |
|---------|----------|------------|------------|------------|
| 1 | John Doe | 456.4567 | 987.1467 | 987.1756 |
Fiddle here.
Also note that you can remove u.name if u.user_id determines u.name... which is most likely the case as it seems to be a primary key. That would speed things up a little bit.
Note: This assumes that you cant have more than one same type for the same user (as it is in your example data, which only has one column for home, work and mobile.
Use user_contact_phones.type to get exact what you want, like-
SELECT a.user_id,
b.area_code, b.phone_number
FROM users a
INNER JOIN user_contact_phones b ON a.user_id = b.user_id where b.type='Home'
Here's a solution that will work:
select u.user_id, u.name,
thome.area_code as home_area_code, thome.phone_number as home_phone_number,
twork.area_code as work_area_code, twork.phone_number as work_phone_number,
tmobi.area_code as mobi_area_code, tmobi.phone_number as mobi_phone_number
from table1 u
left outer join table2 thome on u.user_id = thome.user_id and thome.type = 'Home'
left outer join table2 twork on u.user_id = twork.user_id and twork.type = 'Work'
left outer join table2 tmobi on u.user_id = tmobi.user_id and tmobi.type = 'Mobi'
Please note the use of left outer join instead of inner join in case the record for a particular type does not exist. You will get null values for those columns in your result set with left outer join. With inner join, you would not get a result for a user that did not have all three types. Good luck!
I am trying to query 6 separate tables in my mysql database, the structures are as follows;
item
itemitemid | item | description | brand | date | time | path |
actor
actoractorid | name | actorthumb | bio |
brand
brandbrandid | brandname | description | image |
movie
moviemovieid | title | genre | year | moviethumb | synopsis|
users
userid | name | surname | email | password |
request
requestid | userid | itemid | brandid | movieid | actorid | content | requestdate |
Using the following query I can display for example where the requestid=1 I can see the movie in the request, the actor in the movie, the item of clothing they were wearing and its brand.
$requestid = mysql_real_escape_string($_GET['requestid']);
$query = "select r.requestid, m.*, a.*, i.*, b.*
FROM request r INNER JOIN movie m ON m.movieid = r.movieid
INNER JOIN actor a ON a.actorid = r.actorid
INNER JOIN item i ON i.itemid = r.itemid
INNER JOIN brand b ON b.brandid = r.brandid
WHERE r.requestid = $requestid";
However when I try to echo out "content" and "request date" from the request table. The data simply doesn't appear. I also cannot get the info from the user table, e.g the user logging the request by by adding the following join;
$query = "select r.requestid, m., a., i., b., u.*
INNER JOIN users u ON u.userid = r.userid
Please advise?
You aren't SELECTing those fields. Right now, you're only SELECTing r.requestid from the requests table. You need to add references to every field you want to echo.
As far as the User join, you just seem to be joining on the wrong field. You need to join on u.userid = r.userid. Right now, you're joining on u.itemid which doesn't exist. You'll also need to change your SELECT statement to report the fields you want (e.g. SELECT ... , u.name, u.email).
As an aside, you should avoid SELECTing table.* where possible. This can break things when you add a field to a table but don't account for that when processing the results of a query. You should try to be explicit as possible, and SELECT only the fields you want to use - e.g. SELECT users.name, users.email rather than doing SELECT users.*.