I don't know if this is a problem with my query, or if I am using the wrong thing altogether.
Basically I have 2 tables, submission_data and codes. The codes can be managed in the system, and numbers are submitted against each code in the submissions page. However, if a new code is added after some submissions have been added, the query I use to grab all of the data for a specific submission does not show any new codes added as it is not present in the submission_data table.
SQLFIDDLE
My query is as follows:
SELECT c.code, sd.code_value from submission_data sd
LEFT JOIN codes c ON c.ID = sd.code_id
WHERE submission_id = 1
I should be seeing the S code in the results, obvsiously with a value of 0 as there are no entries.
Have I done the query the wrong way around (selecting from the wrong table first), or is it something to do with my JOINS? I have tried different combinations and keep getting the same results
This query should work:
SELECT c.code, sd.code_value
FROM codes c
LEFT JOIN submission_data sd ON c.ID = sd.code_id AND submission_id = 1
It gets all the rows from codes. For each row from codes it finds all the matches (by code.ID) from submission_data that also have submission_id = 1. If no such row is found in submission_data, it returns NULL for sd.code_value.
Related
I have made an sql fiddle. Users with id 100 and 118 should have 0 records for assigned_scopes, assigned_qa, failed_qa and assigned_canvass. But it does not display that data; it just shows the record for the user with id 210. What I really need is to display all the users, with 0 in each column if they have nothing. How can I do this?
What I have tried since is in this fiddle. It works according to my requirements but there is problem with query optimization; its execution time is not what I want. It took more than 33 seconds to load the page (which is not good at all) when I used the second fiddle query because of the huge data. The query in the first fiddle executed in 2 seconds even with huge data. How can correct the first query to give the results of the second query while (hopefully) staying fast?
The "ten second explanation" for why most queries with LEFT JOIN do not display rows that you expect is that you've put one of the left joined tables into the where clause, demanding a value. This automatically converts any left join into an inner join behaviour
You either have to say WHERE leftjoinedtable.column =value OR leftjoinedtable.column is null or preferentially put the statement in the ON condition (doesn't need a qualifying 'or xxx is null which makes your query simpler and more readable
Move all the statements in your where clause out, and into the respective ON conditions so your query no longer has a where clause section at all. Throw your latter attempt away; it has a Cartesian join and sub selects in the main selection list; in a production system it could be generating millions more rows than needed, selecting extra data based on them, and then discarding them. A very difficult query style to optimise and usually unnecessary
Edit.. Had another look at your fiddle, noticed you also GROUP BY a column that could be null.. When it is, those rows disappear from the output
In terms of how you should write queries, consider first which tables will always have all the values. In your case these are the user and teams tables. These should be inner joined together first, then other tables which may not always have a matching row should be added LEFT join. Right join is seldom needed
Alter the order of your tables so it's teams, inner join users, then left join the two tables you're counting stars on. When you group by, group on the users Id from the users table, not the stats table
I did this with your fiddles but couldn't find a way to save them as a new fiddle on the iPad, couldn't copy the text, but here's a screenshot of a query that does what you require, I'll leave the typing as an exercise for the reader :) , don't forget to adjust the group by
Note, now the users table is inner joined, the =15 filter could go in the where clause... I'll leave the general advice though, to encourage and remind you that a) it works just as well in the ON clause and b) to prefer putting these things in the ON because it means left joins work as you expect
Read a definition of left join on. It returns rows that inner join on does plus unmatched rows in the left table extended by nulls.
Re your 1st link query: If you want all the records from user then it must be the leftmost table in your left joins. You must not remove rows that might have null values by tests requiring non-null values in where--but, why would you?--ie, why do you? The following returns rows only for users with role 15, per the 2nd link query; you don't explain why 15 tested for in the 1st.
select u.user_id,
ut.name as team_name,
/* ... */
count(case when a.status = 2 AND a.qc_id = 0 and o.class_id= 3 then 1 else null end)
AS assigned_canvass
from am_user u
left join user_team ut
on u.user_team_id = ut.user_team_id
left join am_ts_assignment a
on u.user_id = a.tech_id
left join am_ts_order o
on o.assignment_id = a.assignment_id
where u.user_role_id = 15
group by u.user_id
order by u.user_id asc
Compose your queries incrementally and test as you add joins & columns.
(This is the same query I gave on your last post re essentially your 1st link query except it returns a row for every am_user instead of every am_ts_assignment, per each post. The where might have been an and in the first left join with am_user; either will do here.)
I'm using 3 tables to collect data from. The proces looks like:
User write VIN to form
Script search in table 1 for case_id and country base on that vin
number
After that he use case_id and country for search in table number 2
and get calculation id from there
Base on that calculation id and case id it search in 3th table
.
My script looks like this:
SELECT
cases.case_id,
cases.lastcalc_model_options,
cases.country,
calculations.calculation_id,
calculations.license,
positions.text
FROM cases
INNER JOIN calculations ON(cases.case_id =calculations.case_id
AND cases.country = calculations.country)
INNER JOIN positions ON(calculations.case_id = positions.case_id
AND calculations.calculation_id = positions.calculation_id)
WHERE vin ='ABCDEFGH'
This select work correctly, problem start when for example there is for example no result in table positions with that case_id and calculation_id. Instead of give back atleast everything it found in other tables it return NOTHING.
Is there a way to change this kind of komplex SELECT to return everything it found not return something only when every condition is TRUE?
Your problem is the INNER JOIN. Using INNER JOIN your result only contains entries present in all tables. Try using LEFT JOIN instead.
SELECT
cases.case_id,
cases.lastcalc_model_options,
cases.country,
calculations.calculation_id,
calculations.license,
positions.text
FROM cases
LEFT JOIN calculations ON(cases.case_id =calculations.case_id
AND cases.country = calculations.country)
LEFT JOIN positions ON(calculations.case_id = positions.case_id
AND calculations.calculation_id = positions.calculation_id)
WHERE vin ='ABCDEFGH'
See this stackoverlow answer for some more indepth information.
INNER JOIN returns rows from both tables only if there is a match between the columns in both tables.
You may try LEFT JOIN or FULL OUTER JOIN instead.
I have two tables. One of them named files and there is al list of all files. the second table called payments, and there is in there a list of payments for some files.
Payments:
id | fileid | {...}
1 2
2 3
3 2
Files:
id | {...}
1
2
3
I want to select all files, and join the table payments to order by count of this table.
In this case, the first row will be file #2, because it repeats the most in the payments table.
I tried to do it, but when I do it - not all of the rows are shown!
I think it happens because not all of the files are in the payments table. So in this case, I think that it won't display the first row.
Thanks, and sorry for my English
P.S: I use mysql engine
** UPDATE **
My Code:
SELECT `id`,`name`,`size`,`downloads`,`upload_date`,`server_ip`,COUNT(`uploadid`) AS numProfits
FROM `uploads`
JOIN `profits`
ON `uploads`.`id` = `profits`.`uploadid`
WHERE `uploads`.`userid` = 1
AND `removed` = 0
ORDER BY numProfits
As others have noted you need to use LEFT JOIN. - This tells MySQL that entries from the tables to the left should be included even if no corresponding entries exists in the table on the right.
Also you should use GROUP BY to indicate how the COUNT should be deliminated.
So the SQL should be something like;
SELECT Files.ID, count(Payments.FileID) as numpays FROM
Files
LEFT OUTER JOIN
Payments
ON Files.id=Payments.FileID
GROUP BY files.ID
ORDER BY numpays desc
SQL Fiddle
Try this:
select B.fileid,A.{}.....
from
(select id,.....
from files A
inner join
(select count(*),fileid,.....
from payments
group by fileid) B
on files.id=payments.fileid)
I hope this helps. I'm assuming that all ID in files table are unique. In this answer, you can apply an order by clause as per your wish. I've left the select statement to you to select whatever data you want to fetch.
As far as your problem is described, I think this should work. If any problems, do post a comment.
Try LEFT JOIN - in MySQL, the default JOIN is actually an INNER JOIN. In an INNER JOIN, you will only get results back that are in both sides of the join.
See: Difference in MySQL JOIN vs LEFT JOIN
And, as noted in the comments, you may need a GROUP BY with your COUNT as well, to prevent it from just counting all the rows that come back.
I'm having an issue getting this SQL query to work properly.
I have the following query
SELECT apps.*,
SUM(IF(adtracking.appId = apps.id AND adtracking.id = transactions.adTrackingId, transactions.payoutAmount, 0)) AS 'revenue',
SUM(IF(adtracking.appId = apps.id AND adtracking.type = 'impression', 1, 0)) AS 'impressions'
FROM apps, adtracking, transactions
WHERE apps.userId = '$userId'
GROUP BY apps.id
Everything is working, HOWEVER for the 'impressions' column I am generating in the query, I am getting a WAY larger number than there should be. For example, one matching app for this query should only have 72 for 'Impressions' yet it is coming up with a value of over 3,000 when there aren't even that many rows in the adtracking table. Why is this? What is wrong here?
Your problem is you have no join conditions, so you are getting every row of every table being joined in your query result - called a cartesian product.
To fix, change your FROM clause to this:
FROM apps a
LEFT JOIN adtracking ad ON ad.appId = a.id
LEFT JOIN transactions t ON t.adTrackingId = ad.id
You haven't provided the schema for your tables, so I guessed the names of the relevant columns - you may have to adjust them. Also, your transaction table may join to adtracking - it's impossible to know from your question, so agin you have have to alter things slightly. Hopefully you get the idea.
Edit:
Note: your group-by clause is incorrect. You either need to list every column of apps (not recommended), or change your select to only select the id column from apps (recommended). Change your select to this:
SELECT apps.id,
-- rest of query the same
Otherwise you'll get weird, incorrect, results.
I have a query that returns results related to items that match a specific category...
There are 3 mysql tables that results to this, items, categories and item_categories.
These i assume are self explanatory, but the latter, is a linking table that links any specific item to any specific category, using a match of id's.
The items table contains one row, with an id value of 1.
The categories table is filled with 15 rows, with id values of 1-15.
the item_categories table contains one row, the item_id value is 1 and the category_id value is 5.
This is the mysql query in its php form:
$catResultQuery = "
SELECT i.id, name, price
FROM items i
INNER JOIN item_categories
ON i.id = item_id
INNER JOIN categories c
ON category_id = c.id
WHERE MATCH (c.id)
AGAINST ('{$_SESSION['input']}' IN BOOLEAN MODE)
ORDER BY name
";
The session variable has a value of 5, but for some reason, this query displays a 0 result set.
Even when i run the query in php myadmin, it returns 0 rows.
And i am confused, because in my head, the logic behind all of this seems fairly simple, but for some reason i get 0? Does anyone have any idea where i have gone wrong with this?
Any advice and input would be greatly appreciated, thank you!!
Ok, I see now that you're building the SQL dynamically. If that's the case, then this should work:
SELECT i.id, name, price
FROM items i
INNER JOIN item_categories
ON i.id = item_id
INNER JOIN categories c
ON category_id = c.id
WHERE c.id
IN ('{$_SESSION['input']}')
ORDER BY name
Just make sure '{$_SESSION['input']}' is comma delimited and be aware that this carries the risk of SQL injection because you're constructing the SQL on the fly.