I have the following schema in MySQL (read only permissions database)
http://sqlfiddle.com/#!9/1eafc/1
As you can see there are only 5 country codes:
GB, USA, GR, ES, DE
Some months some of the records might not contain one of the countries because no record was created for this country that month.
As you can see in the sqlfiddle, GB records were only created in September.
Is there any way if there isn't any record for a country in that month, instead of not being returned, to show 0 or NULL or something?
I've tried so far different variations of ISNULL, IFNULL and COALESCE but none of them worked.
I want to return something like the following
UK 0
USA 13
GR 5
ES 12
DE 1
Any ideas?
Ok, so in lieu of a functional SQLFiddle I will make a few assumptions. The country code exists in the same table as the grouped data.
If that is the case, why not use:
select DT1.CountryCode, count(DT2.ValueForCounting) as ReturnedCount
from (
select distinct CountryCode
from DataTable ) DT1
left join DataTable DT2
on DT1.CountryCode = DT2.CountryCode
and DT2.QueryConditions = 'Stuff' -- Use the join condition instead of a where clause for anything to do with DT2
your fiddle link not loading,
but i guess my two different ideas about that,
create function and manage it using if condition.
or
create view among month, country and mapping table and put month on left join
hope it works.
Related
Here is a table
id date name
1 180101 josh
2 180101 peter
3 180101 julia
4 180102 robert
5 180103 patrick
6 180104 josh
7 180104 adam
I need to get all the names whom having the same days as 'josh'. how can i achieve it without groupping the whole table together. i need to keep it efficient (this is not my real table, i just simplified my problem here, and i have hundred thousands of records, and 99% of the rows have different dates, so groupable rows by date is kind of rare).
So basicaly what i want is: if 'josh' is the target, i need to get 'josh,peter,julia,adam' (actually the first 10 distinct names sharing the same date with josh).
SELECT
COUNT(date) as datecount,
GROUP_CONCAT(DISTINCT name) as names,
FROM
table
GROUP BY
date
HAVING
datecount>1
// && name IN ('josh') would work nice for me, but im getting error because 'name' is not in GROUPED BY
LIMIT 10
Any idea ? As i mentioned it needs to be fast, and most of the rows have unique dates
Join the table with itself on date:
select distinct t1.name
from tbl t1
join tbl t2 using (date)
where t2.name = 'josh'
Demo
For the best performance you would have indexes on (name) and (date, name).
I'm doing a join between two tables to push criteria values into a record description. The problem is some records do not have some/all criteria and the entire string fails:
Select Concat(Description,'<br><br>',C.CritieraNameA,': ',T.CriteriaValueA,'<br><br>',C.CriteriaNameB,': ',T.CriteriaValueB)
From Records T
Inner Join Company C
On T.CompanyID=C.ID
so I end up with
Supermarket specializing in Dairy Products
Hours: 8am-5pmCredit Cards: Yes
and
Gone with the Wind
Running Time: Too long
Format: DVD
This works fine until I hit a record where either
There is no CriteriaTypeA or CriteriaTypeB in the Company Table
There is no CriteriaValueA or CriteriaValueB in the Records Table
Is there a way to do this select so when it doesn' find a CriteriaValue in Records:
Supermarket specializing in Meats
Hours:
Credit Cards: Yes
or a CriteriaName in Company:
Porsche
Type: Sports Car
It does not simply return an empty result?
IfNull could be useful in this case - it will detect a null and replace it with a value you supply.
IFNULL(CriteriaTypeA , "not given")
Concat_WS to the rescue:
Concat_WS('',C.CriteriaTypeA,': ',T.CriteriaValue)
This should do it:
Select Concat(
Description,
Coalesce(Concat('<br><br>',C.CritieraNameA,': ',T.CriteriaValueA), ''),
Coalesce(Concat('<br><br>',C.CriteriaNameB,': ',T.CriteriaValueB), '')
)
From Records T
Inner Join Company C
On T.CompanyID=C.ID
But as I wrote in the comment: Don't implement output logic in SQL.
i'm having some trouble with trying to extract some data from several MySQL tables in a join statement.
My tables and attributes are:
appointment_end_time (table)
appointment_end_time_id (int)(pk)(ai)
appointment_end_date (datetime)
appointment_start_time (table)
appointment_date_id (int)(pk)(ai)
appointment_start_date (datetime)
instructor(table)
instructor_id (int)(pk)(ai)
firstname varchar(45)
lastname varchar(45)
appointment_timetable
appointment_timetable_id int(11) AI PK
instructor_id int(11) FK
appointment_date_id int(11) FK
appointment_end_time_id int(11) FK
SELECT a.appointment_timetable_id, i.instructor_id, ad.appointment_start_date, aet.appointment_end_date
FROM db12405956.appointment_timetable a
JOIN instructor i on i.instructor_id = a.instructor_id
JOIN appointment_start_time ad on ad.appointment_date_id = a.appointment_date_id
JOIN appointment_end_time aet on aet.appointment_end_time_id = a.appointment_end_time_id
ORDER BY a.appointment_timetable_id;
However, this code brings back no rows selected when executed so i'm wondering what i'm doing wrong, any help will be much appreciated
Sample rows:
(appointment_end_time)
appointment_end_time_id appointment_end_date
1 2016-12-26 14:00:00
2 2016-12-24 13:00:00
3 2016-12-26 13:00:00
(appointment_start_time)
appointment_date_id appointment_start_date
1 2016-12-26 15:00:00
2 2016-12-24 16:00:00
3 2016-12-26 15:30:00
instructor_id firstname lastname
1 Sasha Thompson
2 Laura Robinson
3 John Walters
appointment_timetable
appointment_timetable_id instructor_id appointment_date_id appointment_end_time_
1 Blank Blank Blank
2 Blank Blank Blank
3 Blank Blank Blank
What you need is to learn how to diagnose the problem yourself. It is a common problem that a query doesn't return the expected results and you should understand how to break things down to find the issue.
Let's start with your query:
SELECT a.appointment_timetable_id, i.instructor_id, ad.appointment_start_date, aet.appointment_end_date
FROM db12405956.appointment_timetable a
JOIN instructor i on i.instructor_id = a.instructor_id
JOIN appointment_start_time ad on ad.appointment_date_id = a.appointment_date_id
JOIN appointment_end_time aet on aet.appointment_end_time_id = a.appointment_end_time_id
ORDER BY a.appointment_timetable_id;
What you do to break it down is start with the first table and then add the joins (and where conditions although you don't have any here), one at a time until the data problem appears. I find this easiest to do by using select * or select top 1 * (Or top 10 as I usually prefer to see more than one record) instead of the field list because then you don't have to look for the fields that are associated with joins you haven't added in yet.
So start with
SELECT top 10 *
FROM db12405956.appointment_timetable a
Then try
SELECT top 10 *
FROM db12405956.appointment_timetable a
JOIN instructor i on i.instructor_id = a.instructor_id
Then
SELECT top 10 *
FROM db12405956.appointment_timetable a
JOIN instructor i on i.instructor_id = a.instructor_id
JOIN appointment_start_time ad on ad.appointment_date_id = a.appointment_date_id
Finally
SELECT top 10 *
FROM db12405956.appointment_timetable a
JOIN instructor i on i.instructor_id = a.instructor_id
JOIN appointment_start_time ad on ad.appointment_date_id = a.appointment_date_id
JOIN appointment_end_time aet on aet.appointment_end_time_id = a.appointment_end_time_id
ORDER BY a.appointment_timetable_id;
At some point you will see where the records fell out and that is the location of the problem. Then you might need to look at the fields you are joining on and the data in them in your data sets to see why they are not returning any matches. For instance, if you are joining on dates, they may be stored as dates in one table and as varchar in another and date "01/01/2016' is not equal to 'Jan 1, 2016' or sometimes the column has some sort of prefix or suffix not in the other table. Something like PR2345 in one table and 2345 in the other. Sometimes the query is correct and no rows genuinely meet the conditions. This could be because the data is not fully populated yet (think writing a report for a system that is not live yet, no data on completed actions because none have completed yet.) or because the requirement was wrong in some of its assumptions or because there should be no matching records. It could even be a bug in the data entry.
Depending on the nature of the problem, you might need to return all the records or only use select top 1 (since all records are disappearing). Using SELECT * this way will help when you are returning too many or duplicate records as well as sometimes is is the fields not being returning that affect the results set. Note that I am not saying to use SELECT * in your final result set, it is only being used as a diagnostic tool here.
In your case, the problem looks as if it is in the first table. There are blanks for instructor ID and the other fields in your sample, so there is nothing to join on. (You only gave a sample so the rest of the table may not be like this.) If this is a case where the data is not there yet due to the feature that would add it not yet being live, then you can test your query only by adding test data to the table. Be sure to delete this data after you have finished unit testing. If the data should have been there, then you need to look at the insert from the application for a bug.
I hope I will be able to make my problem clear.
Ik have a table called tweets from which I want to extract information for each data in the daterange table. This table holds 142 dates, of which 102 dates have the property trading (day on which market was open) set to 1 (trading=1).
The below query extracts information from the tweets table for 20 companies (identified by sp100_id). The expected resultset therefore contains 20 x 102 = 2,040 rows. However, I only get returned 1,987 rows because for some date-company combinations, the tweets table holds no data. I need these "empty days" to be included in the resultset however. I thought I could accomplish this by using COALESCE(X, 0), returning 0 if there would be no data, but the result is the same: 1,987 rows.
Based on this information and the query below, does anybody know how I can get it to return 102 rows (1 row for each daterange._date with trading=1) for each sp100_id in the tweets table?
SELECT
sp100.sp100_id,
daterange._date,
COALESCE(SUM(IF(tweets.classify1=2, tweets.`retweet_count`, 0)),0) AS `pos-retweet`,
COALESCE(SUM(IF(tweets.classify1=2, tweets.`user-quality`, 0)),0) AS `pos-quality`,
COALESCE(SUM(IF(tweets.classify1=2, tweets.`follow`, 0)),0) AS `pos-follow`,
COALESCE(SUM(IF(tweets.classify1=3, tweets.`retweet_count`, 0)),0) AS `neg-retweet`,
COALESCE(SUM(IF(tweets.classify1=3, tweets.`user-quality`, 0)),0) AS `neg-quality`,
COALESCE(SUM(IF(tweets.classify1=3, tweets.`follow`, 0)),0) AS `neg-follow`
FROM
sp100
CROSS JOIN
daterange
LEFT JOIN
tweets
ON tweets.nyse_date = daterange._date
AND tweets.sp100_id = sp100.sp100_id
WHERE sp100.sp100_id BETWEEN 1 AND 20 AND tweets.type != 1 AND daterange.trading = 1
GROUP BY
sp100.sp100_id, daterange._date
In any other case, I would provide you with a SQLFiddle, but it would be a lot of work to export a proper portion of the tables used to SQLFiddle while the solution might be clear to some real SQL guru anyway :-)
The problem comes from requiring that tweets.type != 1 in your WHERE clause.
For the dates that have no associated tweets, the outer join will result in all tweets columns, including tweets.type, being NULL. As documented under Working with NULL Values:
Because the result of any arithmetic comparison with NULL is also NULL, you cannot obtain any meaningful results from such comparisons.
In MySQL, 0 or NULL means false and anything else means true. The default truth value from a boolean operation is 1.
Therefore such records are filtered by your WHERE clause.
As #Martin Smith commented, you can move this filter criterion into the ON clause of your outer join (so that the test is performed only against actual tweets records rather than simulated NULL ones).
Alternatively, you could rewrite the filter to handle NULL. For example, using the NULL-safe equality operator:
NOT tweets.type <=> 1
As an aside, I usually don't bother with a daterange table and instead omit dates for which there is no data from the resultset: instead, I handle missing dates within my application code.
You need a calendar table filled with each day. I know it might sound silly, but this solution solves yo a lot of problems. The same solution you can have also with integers ( integer tables)
Evening folks,
I have a complex MySQL COUNT query I am trying to perform and am looking for the best way to do it.
In our system, we have References. Each Reference can have many (or no) Income Sources, each of which can be validated or not (status). We have a Reference table and an Income table - each row in the Income table points back to Reference with reference_id
On our 'Awaiting' page (the screen that shows each Income that is yet to be validated), we show it grouped by Reference. So you may, for example, see Mr John Smith has 3 Income Sources.
We want it to show something like "2 of 3 Validated" beside each row
My problem is writing the query that figures this out!
What I have been trying to do is this, using a combination of PHP and MySQL to bridge the gap where SQL (or my knowledge) falls short:
First, select a COUNT of the number of incomes associated with each reference:
SELECT `reference_id`, COUNT(status) AS status_count
FROM (`income`)
WHERE `income`.`status` = 0
GROUP BY `reference_id`
Next, having used PHP to generate a WHERE IN clause, proceed to COUNT the number of confirmed references from these:
SELECT `reference_id`, COUNT(status) AS status_count
FROM (`income`)
WHERE `reference_id` IN ('8469', '78969', '126613', ..... etc
AND status = 1
GROUP BY `reference_id`
However this doesn't work. It returns 0 rows.
Any way to achieve what I'm after?
Thanks!
In MySQL, you can SUM() on a boolean expression to get a count of the rows where that expression is true. You can do this because MySQL treats true as the integer 1 and false as the integer 0.
SELECT `reference_id`,
SUM(`status` = 1) AS `validated_count`,
COUNT(*) AS `total_count`
FROM `income`
GROUP BY `reference_id`