Pre-Info: In our company a person is marked * if he is actively working. And there are people who changed their departments.
For a report I use 2 tables named COMPANY_PERSON_ALL and trifm_izinler4, joining person_id field as below.
I want to discard (don't list) the row, if the first inner select returns null.
And I want to prevent the second inner select returning multiple Departments.
select izn.person_id, izn.adi_soyadi, izn.company_id,
(select a.employee_status from COMPANY_PERSON_ALL a where a.employee_status = '*' and a.person_id = izn.person_id) as Status,
(select a.org_code from COMPANY_PERSON_ALL a where a.person_id = izn.person_id) as Department,
izn.hizmet_suresi, izn.kalan_izin
from trifm_izinler4 izn
where trunc(rapor_tarihi) = trunc(SYSDATE)
Can you help me how to overcome these 2 problems of inner select statements?
Assuming you only want to see the department from the active person record, you can just join the two tables instead of using subquery expressions, and filter on that status:
select izn.person_id, izn.adi_soyadi, izn.company_id,
a.employee_status as status, a.org_code as department
izn.hizmet_suresi, izn.kalan_izin
from trifm_izinler4 izn
join company_person_all a on a.person_id = izn.person_id
where rapor_tarihi >= trunc(SYSDATE)
-- and rapor_tarihi < trunc(SYSDATE) + 1 -- probably not needed
and a.employee_status = '*'
I've also changed the date comparison; if you compare using trunc(rapor_tarihi) then a normal index on that column can't be used, so it's generally better to compare the original value against a range. Since you're comparing against today's date you probably only need to look for values greater than midnight today, but if that column can have future dates then you can put an upper bound on the range of midnight tomorrow - which I've included but commented out.
If a person can be active in more than one department at a time then this will show all of those, but your wording suggests people are only active in one at a time. If you want to see a department for all active users, but not necessarily the one that has the active flag (or if there can be more than one active), then it's a bit more complicated, and you need to explain how you would want to choose which to show.
Related
So I have complicated query, to simplify let it be like
SELECT
t.*,
SUM(a.hours) AS spent_hours
FROM (
SELECT
person.id,
person.name,
person.age,
SUM(contacts.id) AS contact_count
FROM
person
JOIN contacts ON contacts.person_id = person.id
) AS t
JOIN activities AS a ON a.person_id = t.id
GROUP BY t.id
Such query works fine in MySQL, but Postgres needs to know that GROUP BY field is unique, and despite it actually is, in this case I need to GROUP BY all returned fields from returned t table.
I can do that, but I don't believe that will work efficiently with big data.
I can't JOIN with activities directly in first query, as person can have several contacts which will lead query counting hours of activity several time for every joined contact.
Is there a Postgres way to make this query work? Maybe force to treat Postgres t.id as unique or some other solution that will make same in Postgres way?
This query will not work on both database system, there is an aggregate function in the inner query but you are not grouping it(unless you use window functions). Of course there is a special case for MySQL, you can use it with disabling "sql_mode=only_full_group_by". So, MySQL allows this usage because of it' s database engine parameter, but you cannot do that in PostgreSQL.
I knew MySQL allowed indeterminate grouping, but I honestly never knew how it implemented it... it always seemed imprecise to me, conceptually.
So depending on what that means (I'm too lazy to look it up), you might need one of two possible solutions, or maybe a third.
If you intent is to see all rows (perform the aggregate function but not consolidate/group rows), then you want a windowing function, invoked by partition by. Here is a really dumbed down version in your query:
.
SELECT
t.*,
SUM (a.hours) over (partition by t.id) AS spent_hours
FROM t
JOIN activities AS a ON a.person_id = t.id
This means you want all records in table t, not one record per t.id. But each row will also contain a sum of the hours for all values that value of id.
For example the sum column would look like this:
Name Hours Sum Hours
----- ----- ---------
Smith 20 120
Jones 30 30
Smith 100 120
Whereas a group by would have had Smith once and could not have displayed the hours column in detail.
If you really did only want one row per t.id, then Postgres will require you to tell it how to determine which row. In the example above for Smith, do you want to see the 20 or the 100?
There is another possibility, but I think I'll let you reply first. My gut tells me option 1 is what you're after and you want the analytic function.
What Im looking to do is select data from a postgres table, which does not appear in another. Both tables have identical columns, bar the use of boolean over Varchar(1) but the issue is that the data in those columns do not match up.
I know I can do this with a SELECT EXCEPT SELECT statement, which I have implemented and is working.
What I would like to do is find a method to flag the columns that do not match up. As an idea, I have thought to append a character to the end of the data in the fields that do not match.
For example if the updateflag is different in one table to the other, I would be returned '* f' instead of 'f'
SELECT id, number, "updateflag" from dbc.person
EXCEPT
SELECT id, number, "updateflag":bool from dbg.person;
Should I be joining the two tables together, post executing this statement to identify the differences, from whats returned?
I have tried to research methods to implement this but have no found anything on the topic
I prefer a full outer join for this
select *
from dbc.person p1
full join dbg.person p2 on p1.id = p2.id
where p1 is distinct from p2;
The id column is assumed the primary key column that "links" the two tables together.
This will only return rows where at least one column is different.
If you want to see the differences, you could use a hstore feature
select hstore(p1) - hstore(p2) as columns_diff_p1,
hstore(p2) - hstore(p1) as columns_diff_p2
from dbc.person p1
full join dbg.person p2 on p1.id = p2.id
where p1 is distinct from p2;
Hello everyone I have to get data from and to date, I tried using between clause which fails to retrieve data what I need. Here is what I need.
I have table called hall_info which has following structure
hall_info
id | hall_name |address |contact_no
1 | abc | India |XXXX-XXXX-XX
2 | xyz | India |XXXX-XXXX-XX
Now I have one more table which is events, that contains data about when and which hall is booked on what date, the structure is as follows.
id |hall_info_id |event_date(booked_date)| event_name
1 | 2 | 2015-10-25 | Marriage
2 | 1 | 2015-10-28 | Marriage
3 | 2 | 2015-10-26 | Marriage
So what I need now is I wanna show hall_names that are not booked on selected dates, suppose if user chooses from 2015-10-23 to 2015-10-30 so I wanna list all halls that are not booked on selected dates. In above case both the halls of hall_info_id 1 and 2 ids booked in given range but still I wanna show them because they are free on 23,24,27 and on 29 date.
In second case suppose if user chooses date from 2015-10-25 and 2015-10-26 then only hall_info_id 2 is booked on both the dates 25 and 26 so in this case i wanna show only hall_info_id 1 as hall_info_id 2 is booked.
I tried using inner query and between clause but I am not getting required result to simply i have given only selected fields I have more tables to join so i cant paste my query please help with this. Thanks in advance for all who are trying.
Some changes in Yasen Zhelev's code:
SELECT * FROM hall_info
WHERE id not IN (
SELECT hall_info_id FROM events
WHERE event_date >= '2015-10-23' AND event_date <= '2015-10-30'
GROUP BY hall_info_id
HAVING COUNT(DISTINCT event_date) > DATE_PART('day', '2015-10-30'::timestamp - '2015-10-23'::timestamp))
I have not tried it but how about checking if the number of bookings per hall is less than the actual days in the selected period.
SELECT * FROM hall_info WHERE id NOT IN
(SELECT hall_info_id FROM events
WHERE event_date >= '2015-10-23' AND event_date <= '2015-10-30'
GROUP BY hall_info_id
HAVING COUNT(id) < DATEDIFF(day, '2015-10-30', '2015-10-23')
);
That will only work if you have one booking per day per hall.
To get the "available dates" for the hall returned, your query needs a row source of all possible dates. For example, if you had a calendar table populated with possible date values, e.g.
CREATE TABLE cal (dt DATE NOT NULL PRIMARY KEY) Engine=InnoDB
;
INSERT INTO cal (dt) VALUES ('2015-10-23')
,('2015-10-24'),('2015-10-25'),('2015-10-26'),('2015-10-27')
,('2015-10-28'),('2015-10-29'),('2015-10-30'),('2015-10-31')
;
The you could use a query that performs a cross join between the calendar table and hall_info... to get every hall on every date... and an anti-join pattern to eliminate rows that are already booked.
The anti-join pattern is an outer join with a restriction in the WHERE clause to eliminate matching rows.
For example:
SELECT cal.dt, h.id, h.hall_name, h.address
FROM cal cal
CROSS
JOIN hall_info h
LEFT
JOIN events e
ON e.hall_id = h.id
AND e.event_date = cal.dt
WHERE e.id IS NULL
AND cal.dt >= '2015-10-23'
AND cal.dt <= '2015-10-30'
The cross join between cal and hall_info gets all halls for all dates (restricted in the WHERE clause to a specified range of dates.)
The outer join to events find matching rows in the events table (matching on hall_id and event_date. The trick is the predicate (condition) in the WHERE clause e.id IS NULL. That throws out any rows that had a match, leaving only rows that don't have a match.
This type of problem is similar to other "sparse data" problems. e.g. How do you return a zero total for sales by a given store on a given date, when there are no rows with that store and date...
In your case, the query needs a source of rows with available date values. That doesn't necessarily have to be a table named calendar. (Other databases give us the ability to dynamically generate a row source; someday, MySQL may have similar features.)
If you want the row source to be dynamic in MySQL, then one approach would be to create a temporary table, and populate it with the dates, run the query referencing the temporary table, and then dropping the temporary table.
Another approach is to use an inline view to return the rows...
SELECT cal.dt, h.id, h.hall_name, h.address
FROM (
SELECT '2015-10-23'+INTERVAL 0 DAY AS dt
UNION ALL SELECT '2015-10-24'
UNION ALL SELECT '2015-10-25'
UNION ALL SELECT '2015-10-26'
UNION ALL SELECT '2015-10-27'
UNION ALL SELECT '2015-10-28'
UNION ALL SELECT '2015-10-29'
UNION ALL SELECT '2015-10-30'
) cal
CROSS
JOIN hall_info h
LEFT
JOIN events e
ON e.hall_id = h.id
AND e.event_date = c.dt
WHERE e.id IS NULL
FOLLOWUP: When this question was originally posted, it was tagged with mysql. The SQL in the examples above is for MySQL.
In terms of writing a query to return the specified results, the general issue is still the same in PostgreSQL. The general problem is "sparse data".
The SQL query needs a row source for the "missing" date values, but the specification doesn't provide any source for those date values.
The answer above discusses several possible row sources in MySQL: 1) a table, 2) a temporary table, 3) an inline view.
The answer also mentions that some databases (not MySQL) provide other mechanisms that can be used as a row source.
For example, PostgreSQL provides a nifty generate_series function (Reference: http://www.postgresql.org/docs/9.1/static/functions-srf.html.
It should be possible to use the generate_series function as a row source, to supply a set of rows containing the date values needed by the query to produced the specified result.
This answer demonstrates the approach to solving the "sparse data" problem.
If the specification is to return just the list of halls, and not the dates they are available, the queries above can be easily modified to remove the date expression from the SELECT list, and add a GROUP BY clause to collapse the rows into a distinct list of halls.
This time I thought I had it figured out; but how can my addled brain explain this. No, for this I need the experts.
According to Jeff Atwood A Visual Explanation of SQL Joins Left outer join produces a complete set of records from Table A, with the matching records (where available) in Table B.
SELECT R.[Computer]
,L.[User]
,L.MaxDate
,R.[Notes]
,R.[ID]
From (
SELECT [User], max([StartDate]) as MaxDate
FROM <Table1>
Group by [User]
) As L
Left Outer Join <Table1> as R --Self join
on L.MaxDate = R.StartDate
MaxDate on the left always returns only one date for each User. This should be matched by exactly one matching row on the right. Or so I thought. I am getting multiple items for each date and user.
The purpose here is to return all the columns for each user using MaxDate to get the most recent date for each user. As the dates are unique, I should only get one row for each user, but instead I get several.
How do I limit the result set to the single matching row based on on L.MaxDate = R.StartDate ?
You get multiple matches from R if the same StartDate is found for multiple users. Add User to your join condition.
A question from a beginner.
I have two tables. One (A) contains Start_time, End_time, Status. Second one (B) contains Timestamp, Error_code. Second table is automatically logged by system every few seconds, so it contains lots of non unique values of Error_code (it changes randomly, but within a time range from table A). What i need is to select unique error code for every time range (in my case every row) from the first table for every time range in table A:
A.Start_time, A.End_time B.Error_code.
I have come to this:
select A.Start_time,
A.End_time,
B.Error_code
from B
inner join A
on B.Timestamp between A.Start_time and A.End_time
This is wrong, i know.
Any thoughts are welcome.
If tour query gives a lot of duplicates use distinct to remove them:
select DISTINCT A.Start_time, A.End_time, B.Error_code
from B
inner join A on B.Timestamp between A.Start_time and A.End_time