MySQL Table Diagram:
My query this far:
SELECT tblcourses.CourseStandard,
tblcourses.CourseID,
tblcourses.CourseRef,
tblcourses.CourseStandard,
tblcourses.CourseName,
tblcourses.CourseDuration,
tblcourses.NQFLevel,
tblcourses.CoursePrice,
tblcoursestartdates.StartDate
FROM etcgroup.tblcoursestartdates tblcoursestartdates
INNER JOIN etcgroup.tblcourses tblcourses
ON (tblcoursestartdates.CourseID = tblcourses.CourseID)
WHERE tblcoursestartdates.StartDate >= Now()
If you look at the diagram you will see I have a 3rd table. The query above works fine. It display all the data as it should.
I want to show all the courses and their respective dates excluding those that the student is already booked for. Keep in mind that there can be 20 start dates for 1 course. This is why I am only choosing dates >= Now().
I want to make sure that a student does not get double booked. Yes I can do it afterwards. Beep student already booked BUT if I can have it now show the course dates that the student already booked then great. Any suggestions?
This is pretty straightforward. Presumably you know the StudentID you'd like to see. Do a left join to the bookings table and select the mismatches.
SELECT tblcourses.CourseStandard,
tblcourses.CourseID,
tblcourses.CourseRef,
tblcourses.CourseStandard,
tblcourses.CourseName,
tblcourses.CourseDuration,
tblcourses.NQFLevel,
tblcourses.CoursePrice,
tblcoursestartdates.StartDate
FROM etcgroup.tblcoursestartdates tblcoursestartdates
INNER JOIN etcgroup.tblcourses tblcourses
ON tblcoursestartdates.CourseID = tblcourses.CourseID
AND tblcoursestartdates.StartDate >= Now()
LEFT JOIN tblbookings
ON tblbookings.CourseId = tblcourses.CourseId
AND tblbookings.StudentId = <<<the student ID in question >>>
WHERE tblbookings.BookingID IS NULL
The trick here is the LEFT JOIN ... IS NULL pattern. It eliminates the rows where the ON condition of the LEFT JOIN hit, leaving only the ones where it missed.
Do a left join to tblBookings on courseID where the bookingID is null (there are no matches). You'll have to provide the studentID as a parameter to the query.
SELECT DISTINCT c.CourseStandard,
c.CourseID,
c.CourseRef,
c.CourseStandard,
c.CourseName,
c.CourseDuration,
c.NQFLevel,
c.CoursePrice,
d.StartDate
FROM etcgroup.tblcoursestartdates d
INNER JOIN etcgroup.tblcourses c ON d.CourseID = c.CourseID
LEFT JOIN etcgroup.tblBookings b on c.CourseID = b.CourseID and b.StudentID = #StudentID
WHERE d.StartDate >= Now() and b.bookingID is null
Use NOT EXISTS or NOT IN to find the courses a student has already booked:
SELECT
c.CourseStandard,
c.CourseID,
c.CourseRef,
c.CourseStandard,
c.CourseName,
c.CourseDuration,
c.NQFLevel,
c.CoursePrice,
csd.StartDate
FROM etcgroup.tblcourses c
INNER JOIN etcgroup.tblcoursestartdates csd ON csd.CourseID = tblcourses.CourseID
WHERE csd.StartDate >= Now()
AND c.CourseID NOT IN
(
SELECT CourseID
FROM tblbookings
WHERE StudentID = 12345
);
Related
I have a working knowledge of SQL Server along with the ability to perform most basic queries. However, I'm stuck and needs some help with this one. I have 6 related tables from which I need to derive a set of data.
Tables are as follows:
MTMeterReadings mr
Actual
GroupID
MeterID
CreateDate
MTMeterReadingGroups mg
MeterReadingGroupID
MeterSourceID
EquipmentID
MTMeterSources ms
MeterSourceID
Description
MTMeters m
MeterID
Description
SCEquipment eq
EquipmentID
CustomerID
ARCustomers c
CustomerID
CustomerName
My desired result set is to show the following data for each Actual record in the MTMeterReadins table where mr.CreateDate > 'mm/dd/yyy':
mr.actual | mr.CreateDate | ms.description | e.EquipmentID | c.CustomerName
So far, I've been able to create a query with everything I need except c.CustomerName, but just can't seem to take it all the way (I can be JOIN challenged at times).
Any help with this is greatly appreciated.
I apologize, but I didn't know if the query I already had would be helpful or not.
Here is what I have that yields everything I want except customer name:
SELECT
mg.EquipmentID,
CAST(mr.Actual AS decimal(12, 0)) AS Meter,
CAST(mr.CreateDate AS DATE) AS MeterDate,
ms.MeterSource, m.Description
FROM
MTMeterReadings AS mr
INNER JOIN
MTMeterReadingGroups AS mg ON mr.MeterReadingGroupID = mg.MeterReadingGroupID
INNER JOIN
MTMeterSources AS ms ON mg.MeterSourceID = ms.MeterSourceID
INNER JOIN
MTMeters AS m ON mr.MeterID = m.MeterID
WHERE
(mr.CreateDate >= '01/01/2014') AND (mr.CreateDate <= '02/20/2015')
ORDER BY
MeterDate DESC, mg.EquipmentID, m.Description
However, every attempt that I have made to add CustomerName yields a multiple of the records that I have in the mr table. I can't tell exactly what my error is, but I'm assuming it is an incorrect join. Maybe simple for someone with a bigger SQL brain than me, but this is far from being inside my core knowledge base as I learned SQL from a SAMS "Teach Yourself SQL in 10 Minutes" book.
You are missing additional 2 joins:
SELECT mg.EquipmentID, CAST(mr.Actual AS decimal(12, 0)) AS Meter, CAST(mr.CreateDate AS DATE) AS MeterDate, ms.MeterSource, m.Description, ar.CustomerName
FROM MTMeterReadings AS mr INNER JOIN
MTMeterReadingGroups AS mg ON mr.MeterReadingGroupID = mg.MeterReadingGroupID INNER JOIN
MTMeterSources AS ms ON mg.MeterSourceID = ms.MeterSourceID INNER JOIN
MTMeters AS m ON mr.MeterID = m.MeterID
INNER JOIN SCEquipment eq on mg.EquipmentID = eq.EquipmentID
INNER JOIN ARCustomers ar on eq.CustomerID = ar.CustomerID
WHERE (mr.CreateDate >= '01/01/2014') AND (mr.CreateDate <= '02/20/2015')
ORDER BY MeterDate DESC, mg.EquipmentID, m.Description
It should be as simple as this:
SELECT mg.EquipmentID,
CAST(mr.Actual AS DECIMAL(12, 0)) AS Meter,
CAST(mr.CreateDate AS DATE) AS MeterDate,
ms.MeterSource,
m.Description
c.CustomerName
FROM MTMeterReadings AS mr INNER JOIN
MTMeterReadingGroups AS mg ON mr.MeterReadingGroupID = mg.MeterReadingGroupID INNER JOIN
MTMeterSources AS ms ON mg.MeterSourceID = ms.MeterSourceID INNER JOIN
MTMeters AS m ON mr.MeterID = m.MeterID INNER JOIN
SCEquipment AS e ON mg.EquipmentID = e.EquipmentID INNER JOIN
ARCustomers AS c ON e.CustomerID = c.CustomerID
WHERE (mr.CreateDate BETWEEN '01/01/2014' AND '02/20/2015')
ORDER BY MeterDate DESC,
mg.EquipmentID,
m.Description
But that's assuming that there are no possible outer joins and that every relation you want has at least one record.
Also, note that if mr.CreateDate is a datetime you will miss times on 2/20/2015 after midnight.
I have a query as follows:
SELECT
staff_names.staff_ID AS sid
staff_names.name AS name,
staff_names.rec_type AS rec_type,
prod_staff.specialized AS specialized,
compspec.name AS compspec_name
FROM staff_names JOIN prod_staff USING (staff_ID)
LEFT JOIN (prod_staff_compspec JOIN company_list USING (comp_ID)) compspec
USING (prod_ID, staff_ID, role_ID)
WHERE prod_staff.role_ID = 2
AND prod_staff.prod_ID = 27
AND prod_staff.asst = 'n'
AND episode IS NOT NULL
ORDER BY name
Running this as-is says there's an error near the 'compspec' alias. Removing that and changing 'compspec' to 'company_list' in the SELECT clause returns no rows, even though it should return 1 with the given values. The left join seems to be the problem, but I don't how it should be formatted.
The prod_staff table has prod_ID, staff_ID and role_ID fields. prod_staff_compspec has these and a comp_ID field. prod_staff may or may not have a matching prod_staff_compspec row, but prod_staff_compspec always has a matching company_list row.
What I want to do is retrieve a list of all staff names associated with a given role_ID and prod_ID in the prod_staff table, as well as a company name from the company_list table, if a link to such exists in the prod_staff_compspec table (only a small minority have one).
Switched to ON to define the table relations. LEFT JOIN (prod_staff_compspec JOIN company_list USING (comp_ID)) compspec is switched to 2 left join.
select a.staff_id sid, a.name, a.rec_type, b.specialized, d.name compspec_name
from staff_names a
join prod_staff b on a.staff_id = b.staff_id
left join prod_staff_compspec c on b.prod_id = c.prod_id and b.staff_id = c.staff_id and b.role_id = c.role_id
left join company_list d on c.comp_id = d.comp_id
where b.role_id = 2 and b.prod_id = 27 and b.asst = 'n' and episode is not null
order by a.name;
I have 3 tables
person (id, name)
area (id, number)
history (id, person_id, area_id, type, datetime)
In this tables I store the info which person had which area at a specific time. It is like a salesman travels in an area for a while and then he gets another area. He can also have multiple areas at a time.
history type = 'I' for CheckIn or 'O' for Checkout.
Example:
id person_id area_id type datetime
1 2 5 'O' '2011-12-01'
2 2 5 'I' '2011-12-31'
A person started traveling in area 5 at 2011-12-01 and gave it back on 2011-12-31.
Now I want to have a list of all the areas all persons have right now.
person1.name, area1.number, area2.number, area6.name
person2.name, area5.number, area9.number
....
The output could be like this too (it doesn't matter):
person1.name, area1.number
person1.name, area2.number
person1.name, area6.number
person2.name, area5.number
....
How can I do that?
This question is, indeed, quite tricky. You need a list of the entries in history where, for a given user and area, there is an 'O' record with no subsequent 'I' record. Working with just the history table, that translates to:
SELECT ho.person_id, ho.area_id, ho.type, MAX(ho.datetime)
FROM History AS ho
WHERE ho.type = 'O'
AND NOT EXISTS(SELECT *
FROM History AS hi
WHERE hi.person_id = ho.person_id
AND hi.area_id = ho.area_id
AND hi.type = 'I'
AND hi.datetime > ho.datetime
)
GROUP BY ho.person_id, ho.area_id, ho.type;
Then, since you're really only after the person's name and the area's number (though why the area number can't be the same as its ID I am not sure), you need to adapt slightly, joining with the extra two tables:
SELECT p.name, a.number
FROM History AS ho
JOIN Person AS p ON ho.person_id = p.id
JOIN Area AS a ON ho.area_id = a.id
WHERE ho.type = 'O'
AND NOT EXISTS(SELECT *
FROM History AS hi
WHERE hi.person_id = ho.person_id
AND hi.area_id = ho.area_id
AND hi.type = 'I'
AND hi.datetime > ho.datetime
);
The NOT EXISTS clause is a correlated sub-query; that tends to be inefficient. You might be able to recast it as a LEFT OUTER JOIN with appropriate join and filter conditions:
SELECT p.name, a.number
FROM History AS ho
JOIN Person AS p ON ho.person_id = p.id
JOIN Area AS a ON ho.area_id = a.id
LEFT OUTER JOIN History AS hi
ON hi.person_id = ho.person_id
AND hi.area_id = ho.area_id
AND hi.type = 'I'
AND hi.datetime > ho.datetime
WHERE ho.type = 'O'
AND hi.person_id IS NULL;
All SQL unverified.
You're looking for results where each row may have a different number of columns? I think you may want to look into GROUP_CONCAT()
SELECT p.`id`, GROUP_CONCAT(a.`number`, ',') AS `areas` FROM `person` a LEFT JOIN `history` h ON h.`person_id` = p.`id` LEFT JOIN `area` a ON a.`id` = h.`area_id`
I haven't tested this query, but I have used group concat in similar ways before. Naturally, you will want to tailor this to fit your needs. Of course, group concat will return a string so it will require post processing to use the data.
EDIT I thikn your question has been edited since I began responding. My query does not really fit your request anymore...
Try this:
select *
from person p
inner join history h on h.person_id = p.id
left outer join history h2 on h2.person_id = p.id and h2.area_id = h.area_id and h2.type = 'O'
inner join areas on a.id = h.area_id
where h2.person_id is null and h.type = 'I'
To begin with I have 4 tables I am dealing with.
I have a classes table that is a 1->N relationship with a sections table which also has a 1->N relationship with a lessons table.
So to put it in perpective:
Classes
Sections
Lessons
The last table is an activityLog, when the student accesses a lesson this is recorded using the following:
ActivityLog Row -> actorID (user ID), classID, sectionID, lessonID
I want to pull out the last 5 unique lessons the student has visited. I tried using both DISTINCT and GROUP BY without success.
The same records are being returned each time, not the latest classes that they have visited.
Using GROUP BY
SELECT activityLog.actorID, activityLog.activityDate,
strClasses.classID, strClasses.className,
strSections.sectionID, strSections.sectionName,
strLessons.lessonID, strLessons.lessonName
FROM activityLog
LEFT JOIN strClasses ON strClasses.classID = activityLog.classID
LEFT JOIN strSections ON strSections.sectionID = activityLog.sectionID
LEFT JOIN strLessons ON strLessons.lessonID = activityLog.lessonID
WHERE activityLog.activityTypeID = 6 AND activityLog.actorID = 3
GROUP BY activityLog.lessonID
ORDER BY activityLog.activityDate DESC
LIMIT 5
Using DISTINCT
SELECT DISTINCT activityLog.actorID,
strClasses.classID, strClasses.className,
strSections.sectionID, strSections.sectionName,
strLessons.lessonID, strLessons.lessonName
FROM activityLog
LEFT JOIN strClasses ON strClasses.classID = activityLog.classID
LEFT JOIN strSections ON strSections.sectionID = activityLog.sectionID
LEFT JOIN strLessons ON strLessons.lessonID = activityLog.lessonID
WHERE activityLog.activityTypeID = 6 AND activityLog.actorID = 3
ORDER BY activityLog.activityDate DESC
LIMIT 5
I cannot figure out why the latest records are not being displayed.
Based on your change, how does this suit you?
SELECT activityLog.actorID, activityLog.activityDate,
strClasses.classID, strClasses.className,
strSections.sectionID, strSections.sectionName,
strLessons.lessonID, strLessons.lessonName
FROM activityLog
LEFT JOIN strClasses ON strClasses.classID = activityLog.classID
LEFT JOIN strSections ON strSections.sectionID = activityLog.sectionID
LEFT JOIN strLessons ON strLessons.lessonID = activityLog.lessonID
WHERE activityLog.activityTypeID = 6 AND activityLog.actorID = 3
AND activityLog.activityDate = (SELECT MAX(activityDate) FROM activityLog AS lookup WHERE lessonID = activityLog.lessonID)
ORDER BY activityLog.activityDate DESC
LIMIT 5
Based on your description, I'm not sure why you're using LEFT JOIN, but I've left it in just in case.
Try group by like below
GROUP BY activityLog.classID,activityLog.sectionID,activityLog.lessonID
I think it will work, or just sent me create scripts for these I will create that query
Well, there's got to be a datetime in the ActivityLog I hope... so Try this:
Select s.Name, c.ClassName
From Students s
left Join On Classes c
On c.ClassId In
(Select Distinct ClassId From Classes
Where (Select Count(Distinct ClassId) From Classes ic
Join ActivityLog l On l.UserId = s.UserId
And l.ClassId = c.ClassId
Where classId = c.ClassId
And activityDateTime > l.activityDateTime)
< 5)
I have a rather complex-seeming query that will form the basis for an online classroom scheduling tool. My challenge is to develop a method to identify which classes a user is signed up for in the st_schedule table, then deduce from the overall table of classes, st_classes, which other classes are available that don't conflict with the user's current classes.
For example, if a user has an entry in st_schedule assigning them to a class from 8:00am to 9:00am, they would be ineligible for any class whose time fell between 8:00am and 9:00am. A class that ran 7:15am - 8:15am would make the user ineligible. I store the start times and end times of classes in the database separately for comparison purposes. It's important that this be as flexible as possible, so the concept of "blocking" times and assigning times to blocks is not a possibility.
Here are excerpts from the tables:
table st_classes (holds class information)
id
start_time
end_time
table st_schedule (holds schedule information)
id
user_id
class_id
I certainly could do this in a series of loops server-side, but I have to think that there's a MySQL method that can do this type of operation in one fell swoop.
You want to join the two tables together to represent the user's classes, and then find unregistered classes where the start time and end time do not fall between the start and end time of the user's classes.
Something like this. Completely off the cuff and untested:
SELECT
*
FROM
st_schedule s
INNER JOIN st_classes c ON c.id = s.class_id
INNER JOIN st_classes all_classes
ON all_classes.start_time NOT BETWEEN c.start_time AND c.end_time
AND all_classes.end_time NOT BETWEEN c.start_time AND c.end_time
WHERE
s.user_id = 1
Edit: Try #2
I only have a moment to look at this. I think I reversed the second join clauses. The all_classes alias represents the full list of classes, where the "c" alias represents the classes that the student is signed up for.
SELECT DISTINCT
all_classes.*
FROM
st_schedule s
INNER JOIN st_classes c ON c.id = s.class_id
INNER JOIN st_classes all_classes
ON c.start_time NOT BETWEEN all_classes.start_time AND all_classes.end_time
AND c.end_time NOT BETWEEN all_classes.start_time AND all_classes.end_time
WHERE
s.user_id = 1
This is using table variables in mssql but the sql selects should translate over to mysql
First the sample data
DECLARE #st_classes TABLE
(
ID INT NOT NULL,
Title VARCHAR(40) NOT NULL,
StartTime DATETIME NOT NULL,
EndTime DATETIME NOT NULL
)
DECLARE #st_schedule TABLE
(
ID INT NOT NULL,
UserID INT NOT NULL,
ClassID INT NOT NULL
)
INSERT INTO #st_classes (ID, Title, StartTime, EndTime)
SELECT 1,'Class1','08:00:00','09:30:00' UNION
SELECT 2,'Class2','09:30:00','11:30:00' UNION
SELECT 3,'Class3','11:30:00','16:00:00' UNION
SELECT 4,'Class4','16:00:00','17:30:00' UNION
SELECT 5,'Class5','09:00:00','11:45:00' UNION
SELECT 6,'Class6','07:00:00','18:00:00'
INSERT INTO #st_schedule(ID, UserID, ClassID)
SELECT 1,1,1 UNION
SELECT 2,1,2 UNION
SELECT 3,2,6
Next a bit of sql to confirm the tables join OK (selecting scheduled courses for user with an ID of 1) - Returns class 1 and 2
SELECT *
FROM #st_schedule AS S INNER JOIN
#st_classes AS C ON S.ClassID = C.ID
WHERE S.UserID = 1
Now we need to select all the ID of the courses where they overlap time wise with the users scheduled ones (including the scheduled ones) - Returns 1,2,5,6
SELECT AC.ID
FROM #st_classes AS AC
INNER JOIN ( SELECT C.StartTime,
C.EndTime
FROM #st_schedule AS S
INNER JOIN #st_classes AS C ON S.ClassID = C.ID
WHERE S.UserID = 1
) AS UC ON ( AC.StartTime < DATEADD(ss, -1, UC.EndTime)
AND DATEADD(ss, -1, UC.EndTime) > UC.StartTime
)
GROUP BY AC.ID
Now we need to select all courses where the Course ID is not in our list of overlapping course IDs. - Returns course 3 and 4
SELECT *
FROM #st_classes
WHERE ID NOT IN (
SELECT AC.ID
FROM #st_classes AS AC
INNER JOIN ( SELECT C.StartTime,
C.EndTime
FROM #st_schedule AS S
INNER JOIN #st_classes AS C ON S.ClassID = C.ID
WHERE S.UserID = 1
) AS UC ON ( AC.StartTime < DATEADD(ss, -1, UC.EndTime)
AND DATEADD(ss, -1, UC.EndTime) > UC.StartTime
)
GROUP BY AC.ID )
Change the user ID filter to 2 and you should not get any returned as the course assigned to that user overlaps all courses.