Produce a Query viewing multiple tables - sql

I have been given a database, the structure and data values are all unchangable and have been provided with a question.
Produce a query to list the holiday code, holiday description, holiday duration and site description for all holidays which visit site code 101. Your answer must not assume that site code 101 will always have the same site description.
I am confused on how to tackle this question. I have tried Multiple joins, different dot notation and googled the question to hell and back. Any help?
Table 1 - Holiday_Details
Holiday_Code - Country_Visited - Holiday_Duration - Holiday_Desc - Rating_Code - Cost
Table 2 - Site_Of_Holiday
Site_Description - Site_Code
Table 3 - Site_Visited
Holiday_Code - Site_Code
Comments have asked for previous attempts. This was my first.
SELECT holiday_code,
holiday_desc,
holiday_duration site_of_holiday.Site_Name
FROM holiday_details
JOIN site_visited
ON holiday_code = site_visited.holiday_code
JOIN site_of_holiday
ON site_visited.site_code = site_of_holiday.site_code
WHERE site_of_holiday.site_code = 101;

For future reference, you'll get a better response if you post a lot more detail about your failed attempts. By that, I mean code. Using SO to solve your homework assignments is frowned upon but, like a commenter said, once you've wracked your brain we're willing to help.
You seem like you may have actually tried real hard, so I'll throw you a bone...
The trick to navigating multiple tables is to find the "pairs" of matching columns. In this case you want to find a path between the tables Site_Of_Holiday (which has Site_Description) and Holiday_Details (which has everything else).
The columns that match between each pair of tables are:
Holiday_Code is found in both Site_Visited and Holiday_Details
Site_Code is found in both Site_Of_Holiday and Site_Visited
This allows you to build a path between the tables that contain all of the columns we want in the output. You would do this, in this case, using INNER JOINs across those matching column pairs.
Once you've joined the tables, think of the result like a giant table whose columns include all columns from all three tables (prefixed with whatever you 'name' the table during the joins). Now you just filter on the Site_Code with the usual WHERE clause.
Here's the full example - let me know if it works for you:
SELECT hd.Holiday_Code, hd.Holiday_Desc, hd.Holiday_Duration, soh.Site_Description
FROM Holiday_Details hd
INNER JOIN Site_Visited sv ON hd.Holiday_Code = sv.Holiday_Code
INNER JOIN Site_Of_Holiday soh ON sv.Site_Code = soh.Site_Code
WHERE sv.Site_Code = 101
Good luck!
P.S. In case any Americans get a similar assignment, here's the translation ;-)
SELECT vd.Vacation_Code, vd.Vacation_Desc, vd.Vacation_Duration, sov.Site_Description
FROM Vacation_Details vd
INNER JOIN Site_Visited sv ON vd.Vacation_Code = sv.Vacation_Code
INNER JOIN Site_Of_Vacation sov ON sv.Site_Code = sov.Site_Code
WHERE sv.Site_Code = 101

Related

SQL - getting data twice from the same table

Good people of the internet, I need your help!
I'm trying to put together some SQL code to create a report. Basically, I'm needing to look at one table - tbl_Schedules - and fetch the maximum of the field SchedDone, which is a regular date field.
This is fair enough. I manage this using GROUP BY and MAX.
The same table also contains SchedFrom and SchedTo fields, and I need to get this from another record, but run alongside this.
Basically, I need a "LatestDate" field (which shows the max SchedDone), and then a "next scheduled" field (or fields), showing when it is next to be done, pulled from a row where the SchedDone is null.
My current code, displayed below (ignore everything but the tbl_Schedules stuff) is working to an extent. It shows the LatestDate as described above, but also shows the maximum of that Task's SchedFrom and SchedTo. These are all from different rows in the tbl_Schedules, which is what I want. I just need to know how to set up rules for the SchedFrom and SchedTo, preferably without involving any other tables or setting up multiple views.
I do have this working, but it's taking up several views and the speed involved is not good. I'd hope I can get it working in a single chunk of SQL code.
PS - tbl_PhysicalAssets is a one-to-many relationship with tbl_Operations (one row in tbl_PhysicalAssets to many in tbl_Operations), and tbl_Operations is a one-to-many relationship with tbl_Schedules (one row in tbl_Operations to many in tbl_Schedules).
Current code below (again, please ignore the other tables!) -
SELECT
dbo.tbl_PhysicalAsset.FKID_Contract,
dbo.tbl_PhysicalAsset.MyLevel,
dbo.tbl_PhysicalAsset.L1_Name,
dbo.tbl_PhysicalAsset.L2_Name,
dbo.tbl_PhysicalAsset.L3_Name,
dbo.tbl_OpList.Operation_Name,
dbo.tbl_Teams.Team_Name,
MAX(tbl_Schedules_1.SchedDone) AS LatestDate,
MAX(tbl_Schedules_1.SchedFrom) AS Expr1,
MAX(tbl_Schedules_1.SchedTo) AS Expr2
FROM
dbo.tbl_Schedules AS tbl_Schedules_1
RIGHT OUTER JOIN
dbo.tbl_PhysicalAsset
INNER JOIN
dbo.tbl_Operations ON dbo.tbl_PhysicalAsset.PKID_PhysicalAsset = dbo.tbl_Operations.FKID_PhysicalAsset
INNER JOIN
dbo.tbl_OpList ON dbo.tbl_Operations.FKID_Operation = dbo.tbl_OpList.PKID_Op
INNER JOIN
dbo.tbl_Teams ON dbo.tbl_Operations.FKID_Team = dbo.tbl_Teams.PKID_Team ON tbl_Schedules_1.FKID_Operation = dbo.tbl_Operations.PKID_Operation
GROUP BY
dbo.tbl_PhysicalAsset.FKID_Contract,
dbo.tbl_PhysicalAsset.MyLevel,
dbo.tbl_PhysicalAsset.L1_Name,
dbo.tbl_PhysicalAsset.L2_Name,
dbo.tbl_PhysicalAsset.L3_Name,
dbo.tbl_OpList.Operation_Name,
dbo.tbl_Teams.Team_Name
HAVING
(dbo.tbl_PhysicalAsset.FKID_Contract = 6)
AND (dbo.tbl_PhysicalAsset.MyLevel = 3)
This is rough as we don't know the exact details of your table structure.
But basically you need to first write the queries that get the two separate bits of information, make sure they work in isolation. You can then just join them together.
So something like (I've assumed FKID_Operation is the 'common' piece of info):
select
a.FKID_Operation
, b.LatestDate
, c.NextToDate
, c.NextFromDate
from tbl_Schedules a
inner join
(
select
m.FKID_Operation
, Max(m.SchedDone) as LatestDate
from tbl_Schedules m
where SchedDone is not null
) b
on a.FKID_Operation = b.FKID_Operation
inner join
(
select
n.FKID_Operation
, n.SchedTo as NextToDate
, n.SchedFrom as NextFromDate
from tbl_Schedules n
where SchedDone is null
) c
on a.FKID_Operation = c.FKID_Operation
I'd also look into CTE's as they can make this kind of query much easier to understand.

SQL - Getting a column from another table to join this query

I've got the code below which displays the location_id and total number of antisocial crimes but I would like to get the location_name from a different table called location_dim be output as well. I tried to find a way to UNION it but couldn't get it to work. Any ideas?
SELECT fk5_location_id , COUNT(fk3_crime_id) as TOTAL_ANTISOCIAL_CRIMES
from CRIME_FACT
WHERE fk1_time_id = 3 AND fk3_crime_id = 1
GROUP BY fk5_location_id;
You want to use join to lookup the location name. The query would probably look like this:
SELECT ld.location_name, COUNT(cf.fk3_crime_id) as TOTAL_ANTISOCIAL_CRIMES
from CRIME_FACT cf join
LOCATION_DIM ld
on cf.fk5_location_id = ld.location_id
WHERE cf.fk1_time_id = 3 AND cf.fk3_crime_id = 1
GROUP BY ld.location_name;
You need to put in the right column names for ld.location_name and ld.location_id.
you need to find a relationship between the two tables to link a location to crime. that way you could use a "join" and select the fields from each table you are interested in.
I suggest taking a step back and reading up on the fundamentals of relational databases. There are many good books out there which is the perfect place to start.

Way to combine filtered results using LIKE

I have a many to many relationship between people and some electronic codes. The table with the codes has the code itself, and a text description of the code. A typical result set from a query might be (there are many codes that contain "broken" so I feel like it's better to search the text description rather than add a bunch of ORs for every code.)
id# text of code
1234 broken laptop
1234 broken mouse
Currently the best way for me to get a result set like this is to use the LIKE%broken% filter. Without changing the text description, is there any way I can return only one instance of a code with broken? So in the example above the query would only return 1234 and broken mouse OR broken laptop. In this scenario it doesn't matter which is returned, all I'm looking for is the presence of "broken" in any of the text descriptions of that person's codes.
My solution at the moment is to create a view that would return
`id# text of code
1234 broken laptop
1234 broken mouse`
and using SELECT DISTINCT ID# while querying the view to get only one instance of each.
EDIT ACTUALLY QUERY
SELECT tblVisits.kha_id, tblICD.descrip, min(tblICD.Descrip) as expr1
FROM tblVisits inner join
icd_jxn on tblVisits.kha_id = icd_jxn.kha)id inner join tblICD.icd_fk=tblICD.ICD_ID
group by tblVisits.kha_id, tblicd.descrip
having (tblICD.descrip like n'%broken%')
You could use the below query to SELECT the MIN code. This will ensure only text per id.
SELECT t.id, MIN(t.textofcode) as textofcode
FROM table t
WHERE t.textofcode LIKE '%broken%'
GROUP BY t.id
Updated Actual Query:
SELECT tblVisits.kha_id,
MIN(tblICD.Descrip)
FROM tblVisits
INNER JOIN icd_jxn ON tblVisits.kha_id = icd_jxn.kha)id
INNER JOIN tblicd ON icd_jxn.icd_fk = tbl.icd_id
WHERE tblICD.descrip like n'%broken%'
GROUP BY tblVisits.kha_id

relationships produce duplicate records on query, DISTINCT does not work, any other solutions available?

I am new to this portal. I have a very simple problem to be solved. It is related to the ANSI SQL. I am writing a reports using BIRT and I am fetching the data from several tables. I understand how the SQL joins work but maybe not fully. I researched google for hours and I could not find relevant answer.
My problem is that one of the relationships in the code produce a duplicate result (the same row is copied - duplicated). I was so determined to solve it I used every type of join available. Some of this SQL was produced already. I shall post my code below. I know that one of the solutions to my problem is use of the 'DISTINCT' keyword. I have used it and it does not solve my problem.
Can anyone propose any solution to that?
Sample code:
SELECT DISTINCT
partmaster.partdesc,
partmaster.uom,
traders.name AS tradername,
worksorders.id AS worksorderno,
worksorders.partid,
worksorders.quantity,
worksorders.duedate,
worksorders.traderid,
worksorders.orderid,
routingoperations.partid,
routingoperations.methodid,
routingoperations.operationnumber,
routingoperations.workcentreid,
routingoperations.settime,
routingoperations.runtime,
routingoperations.perquantity,
routingoperations.description,
routingoperations.alternativeoperation,
routingoperations.alternativeoperationpreference,
machines.macdesc,
machines.msection,
allpartmaster.partnum,
allpartmaster.nbq,
allpartmaster.partdesc,
routingoperationtools.toolid,
tools.tooldesc,
CAST (emediadetails.data as VARCHAR(MAX)) AS cplandata
FROM worksorders
INNER JOIN partmaster ON worksorders.partid = partmaster.partnum
INNER JOIN traders traders ON worksorders.traderid = traders.id
INNER JOIN routingoperations routingoperations ON worksorders.partid = routingoperations.partid
AND worksorders.routingmethod = routingoperations.methodid
INNER JOIN allpartmaster allpartmaster ON routingoperations.partid = allpartmaster.partnum
LEFT OUTER JOIN machines machines ON routingoperations.workcentreid = machines.macid
LEFT OUTER JOIN routingoperationtools routingoperationtools ON routingoperationtools.partid = routingoperations.partid
AND routingoperationtools.routingmethod = routingoperations.methodid
AND routingoperationtools.operationnumber = routingoperations.operationnumber
LEFT OUTER JOIN tools tools ON tools.toolid = routingoperationtools.toolid
LEFT OUTER JOIN emediadetails ON emediadetails.keyvalue1 = worksorders.id
AND emediadetails.keyvalue2 = routingoperations.operationnumber
AND emediadetails.emediaid = 'worksorderoperation'
I do not have too much of the test data but I know that one row is copied twice as the result of the query below even tho I used DISTINCT keyword. I know that my problem is rather specific and not general but the solution that someone will propose may help others with the similar problem.
I can't solve your problem for you without some test data, but I have some helpful hints.
In principle, you should be really careful with DISTINCT - its a great way of hiding bugs in your query. Only use DISTINCT if you are confident that the underlying data contains legitimate duplicates. If your joins are wrong, and you're getting a cartesian product, you can remove the duplicates from the results with DISTINCT - but that doesn't stop the cartesian product being generated. You'll get very poor performance, and possibly incorrect data.
Secondly, I am pretty sure that DISTINCT works properly - you are almost certainly not getting duplicates, but it may be hard to spot the difference between two rows. Leading or trailing spaces in text columns, for instance could be to blame.
Finally, to work through this problem, I'd recommend building the query up join by join, and seeing where you get the duplicate - that's the join that's to blame.
So, start with:
SELECT
traders.name AS tradername,
worksorders.id AS worksorderno,
worksorders.partid,
worksorders.quantity,
worksorders.duedate,
worksorders.traderid,
worksorders.orderid
FROM worksorders
INNER JOIN traders traders ON
worksorders.traderid = traders.id
and build up to the next join.
Are you sure the results are exact duplicates? Makes sure there isn't one column that actually has a different value.

SUM(a*b) not working

I have a PHP page running in postgres. I have 3 tables - workorders, wo_parts and part2vendor. I am trying to multiply 2 table column row datas together, ie wo_parts has a field called qty and part2vendor has a field called cost. These 2 are joined by wo_parts.pn and part2vendor.pn. I have created a query like this:
$scoreCostQuery = "SELECT SUM(part2vendor.cost*wo_parts.qty) as total_score
FROM part2vendor
INNER JOIN wo_parts
ON (wo_parts.pn=part2vendor.pn)
WHERE workorder=$workorder";
But if I add the costs of the parts multiplied by the qauntities supplied, it adds to a different number than what the script is doing. Help....I am new to this but if someone can show me in SQL I can modify it for postgres. Thanks
Without seeing example data, there's no way for us to know why you're query totals are coming out differently that when you do the math by hand. It could be a bad join, so you are getting more/less records than you expected. It's also possible that your calculations are off. Pick an example with the smallest number of associated records & compare.
My suggestion is to add a GROUP BY to the query:
SELECT SUM(p.cost * wp.qty) as total_score
FROM part2vendor p
JOIN wo_parts wp ON wp.pn = p.pn
WHERE workorder = $workorder
GROUP BY workorder
FYI: MySQL was designed to allow flexibility in the GROUP BY, while no other db I've used does - it's a source of numerous questions on SO "why does this work in MySQL when it doesn't work on db x...".
To Check that your Quantities are correct:
SELECT wp.qty,
p.cost
FROM WO_PARTS wp
JOIN PART2VENDOR p ON p.pn = wp.pn
WHERE p.workorder = $workorder
Check that the numbers are correct for a given order.
You could try a sub-query instead.
(Note, I don't have a Postgres installation to test this on so consider this more like pseudo code than a working example... It does work in MySQL tho)
SELECT
SUM(p.`score`) AS 'total_score'
FROM part2vendor AS p2v
INNER JOIN (
SELECT pn, cost * qty AS `score`
FROM wo_parts
) AS p
ON p.pn = p2v.pn
WHERE p2n.workorder=$workorder"
In the question, you say the cost column is in part2vendor, but in the query you reference wo_parts.cost. If the wo_parts table has its own cost column, that's the source of the problem.