Today while writing one of the many queries that every developer in my company write every day I stumbled upon a question.
The DBMS we are using is Sql Server 2008
Say for example I write a query like this in the usual PERSON - DEPARTMENT db example
select * from person where id = '01'
And this query returns one row:
id name fk_department
01 Joe dp_01
The question is: is there a way (maybe using an addon) to make sql server write and execute a select like this
select * from department where id = 'dp_01'
only by for example clicking with the mouse on the cell containing the fk value (dp_01 in the example query)? Or by right click and selecting something like ("Go to pointed value")?
I hope I didn't wrote something stupid or impossible by definition
Not really, but that seems like a silly thing to do. Why would you want to confuse an id with a department name?
Instead, you could arrange things so you could do:
select p.*
from person p
where department = 'dp_01';
You would do this by adding a computed column department that references a scalar function that looks up the value in the department table. You can read about computed columns here.
However, a computed column would have bad performance characteristics. In particular, it would basically require a full table scan on the person table, even if that is not appropriate.
Another solution is to create a view, v_person that has the additional columns you want. Then you would do:
select p.*
from v_person p
where department = 'dp_01';
Why can't you write yourself by saying
select * from department where id =
(select fk_department from person where id = '01')
Related
Before start, Sorry some of results and datas are written in Korean.
Here is a code that I currently am looking on.
SELECT S.*, D.DNAME
FROM STUDENT S, DEPARTMENT D
WHERE (SUBSTR(S.JUMIN,7,1),S.WEIGHT) IN (SELECT SUBSTR(JUMIN,7,1),MAX(WEIGHT)
FROM STUDENT GROUP BY SUBSTR(JUMIN,7,1))
AND S.DEPTNO1 = D.DEPTNO;
And here is the DEPARTMENT data.
And this is the STUDENT data.
I got a result as I want. But I have some questions when I change this part of the code
WHERE (SUBSTR(S.JUMIN,7,1),S.WEIGHT) IN (SELECT SUBSTR(JUMIN,7,1),MAX(WEIGHT)
into this one
WHERE (SUBSTR(S.JUMIN,7,1),S.WEIGHT) IN (SELECT
S.SUBSTR(JUMIN,7,1),MAX(S.WEIGHT)
What I do is simply put S infront of JUMIN and WEIGHT in line3.
But when I do this it shows me the whole data.
I thought JOIN ALIAS (which are S,D in this code) is used as way show that I have two tables to use that is labeled with S and D. S means this data is in STUDENT and D is in DEPARTMENT.
But I think I get it in a wrong way.
Anyway I have no idea how this result is come out.
This one is referring to your main table not the subquery table.
WHERE (SUBSTR(S.JUMIN,7,1),S.WEIGHT) IN (SELECT
S.SUBSTR(JUMIN,7,1),MAX(S.WEIGHT)
Your original query is already correct. In which you already have a new result set based on your aggregation.
WHERE (SUBSTR(S.JUMIN,7,1),S.WEIGHT) IN (SELECT SUBSTR(JUMIN,7,1),MAX(WEIGHT)
This sounds like a very simple query but I have never needed this calculation before. I'm using SQL Management Studio and SQL Server 2008.
I have a table ct_workers which contains individual employees and a second table cs_facilities which shows the sites that they work at.
The table ct_workers has a field person which is the primary ID for each employee and has a field facility which links the employees to cs_facilities via a field guid
I'm looking to display all workers that have 2 or more facilities.
I've though about using Excel or rownumber but surely that must be a simple efficient way of doing this?
Can anyone assist please?
Thanks,
You can use a GROUP BY with HAVING
SELECT cw.person
FROM ct_workers cw
GROUP BY cw.person
HAVING COUNT(DISTINCT cw.facility) >= 2
Your question suggests that you can use aggregation:
select w.person
from ct_workers w
group by w.person
having min(w.facility) <> max(w.facility); -- at least 2 values
However, if the person is the unique key in ct_workers, then a person can only be in one facility. So, your question would not make sense. You should actually have a junction table with one row per person and per facility.
I am in the process of creating an organizational charts for my company, and to create the chart, the data must have a unique role identifier, and a unique 'reports to role' identifier for each line. Unfortunately my data is not playing ball and it out of my scope to change the source.
I have two source tables, simplified in the image below. It is important to note a couple of things in the data.
An employees manager in the query needs to come from the [EmpData] table. The 'ReportsTo' field is only in the [Role] table to be used when a role is vacant
Any number of employees can hold the same role, but for simplicity lets assume that there will only ever be one person in the 'Reports to' role
Using this sample data, my query is as follows:
/**Join Role table with employee data table.
/**Right join so roles with more than one employee will generate a row each
SELECT [Role].RoleId As PositionId
,[EmpData].ReportsToRole As ReportsToPosition
,[Role].RoleTitle
,[Empdata].EmployeeName
FROM [Role]
RIGHT JOIN [EmpData] ON [Role].RoleId=[EmpData].[Role]
UNION
/** Output all roles that do not have a holder, 'VACANT' in employee name.
SELECT [Role].RoleId
,[Role].ReportsToRole
,[Role].RoleTitle
,'VACANT'
FROM [Role]
WHERE [Role].RoleID NOT IN (SELECT RoleID from [empdata])
This almost creates the intended output, but each operator roles has 'OPER', in the PositionId column.
For the charting software to work, each position must have a unique identifier.
Any thoughts on how to achieve this outcome? I'm specifically chasing the appended -01, -02, -03 etc. highlighted yellow in the Desired Query Output.
If you are using T-SQL, you should look into using the ROW_NUMBER operator with the PARTITON BY command and combining the column with your existing column.
Specifically, you would add a column to your select of ROW_NUMBER () OVER (PARTITION BY PositionID ORDER BY ReportsToPosition,EmployeeName) AS SeqNum
I would add that to your first query, and then, in your second, I would do something like SELECT PositionID + CASE SeqNum WHEN 1 THEN "" ELSE "-"+CAST(SeqNum AS VarChar(100)),...
There are multiple ways to do this, but this will leave out the individual ones that don't need a "-1" and only add it to the rest. The major difference between this and your scheme is it doesn't contain the "0" pad on the left, which is easy to do, nor would the first "OPER" be "OPER-1", they would simply be "OPER", but this can also be worked around.
Hopefully this gets you what you need!
I have a few tables set up in Access as follows (forgive the slightly redundant example content):
Table 1:
- ID
- FirstName
- SecondName
Table 2:
- ID
- Details
- PersonID -> Table 1[ID]
Table 3:
- ID
- Group
- PersonDetails -> Table 2[ID]
Table 1 is the base table containing records and retrieving no other information. For example, it could store someone's first and second names, along with an autonumber ID.
Table 2 contains records which, amongst other things, contain a field that links to Table 1 and stores the ID of one of the records held there. With the lookup wizard I can choose to utilise all fields from Table 1, store the ID of the Table 1 record in the Table 2 field and also display the first and second names in the combobox on the form to make choosing a record more intuitive.
In table 3, I need to store the ID of one of the records in Table 2. However, I would also like to again display in the form combobox the first and second names from the related record (in Table 1) whose ID is stored in Table 2. I can't choose to utilise, for example, the PersonDetails field from table 2 as this just puts ID numbers into the combobox - I'd need to do something equivalent of:
Table 2[ID]->[FirstName]
Is this possible to do with the lookup wizard in Access or would I have to look into queries or VBA?
Thanks.
Your query for your combo should look something like this:
SELECT cp.ID, cp.ReferenceName, c.Company, p.FeePerHour
FROM (ClientProfile AS cp LEFT JOIN Clients AS c ON cp.ClientID = c.ID)
LEFT JOIN Pricing AS p ON cp.PricePlanID = p.ID;
The main problem with your query is that you're missing the Parenthesis that are needed when you have multiple joins. If you had another join, you'd need a second set of parenthesis.
I took some liberty and used table aliases. It makes SQL concise and more readable.
If this query still doesn't work it might be because you're trying to join "child tables" to the "main table" without using your Foreign Key fields as the joining field. If this were my database the SQL would look something like this:
SELECT cp.ClientProfileID, cp.ReferenceName, c.Company, p.FeePerHour
FROM (ClientProfile AS cp LEFT JOIN Clients as C ON cp.ClientID = c.ClientID)
LEFT JOIN Pricing AS p ON cp.ClientProfileID = p.ClientProfileID;
Personally, I basically never use just plain ID as a field name. And when creating a foreign key I usually use the same field name as what the original table has. There are exceptions, especially in the case where you need to link back to the same table more than once. Consider the case where you are tracking real estate properties and you have a Buyer and a Seller that are both entities (but different from each other) in the same People table. You would then need to name them something like BuyerID and SellerID but ultimately they would link back to the PersonID in the Person table.
So Here's the table design I would go for. Notice I changed Group to PriceGroup. Watch out for reserved words when programming, not only in SQL but any language. If you name your field Group at some point you'll be trying to "Group on Group" which sounds and looks bad, if nothing else.
Client:
- ClientID
- FirstName
- SecondName
ClientProfile:
- ClientProfileID
- Details
- ClientID (Foreign Key to Client)
Pricing:
- PricingID
- PriceGroup
- ClientProfileID (Foreign Key to ClientProfile)
I am trying to use a second SELECT to get some ID, then use that ID in a second SELECT and I have no idea how.
SELECT Employee.Name
FROM Emplyee, Employment
WHERE x = Employment.DistributionID
(SELECT Distribution.DistributionID FROM Distribution
WHERE Distribution.Location = 'California') AS x
This post got long, but here is a short "tip"
While the syntax of my select is bad, the logic is not. I need that "x" somehow. Thus the second select is the most important. Then I have to use that "x" within the first select. I just don't know how
/Tip
This is the only thing I could imagine, I'm very new at Sql, I think I need a book before practicing, but now that I've started I'd like to finish my small program.
EDIT:
Ok I looked up joins, still don't get it
SELECT Employee.Name
FROM Emplyee, Employment
WHERE x = Employment.DistributionID
LEFT JOIN Distribution ON
(SELECT Distribution.DistributionID FROM Distribution
WHERE Distribution.Location = 'California') AS x
Get error msg at AS and Left
I use name to find ID from upper red, I use the ID I find FROM upper red in lower table. Then I match the ID I find with Green. I use Green ID to find corresponding Name
I have California as output data from C#. I want to use California to find the DistributionID. I use the DistributionID to find the EmployeeID. I use EmployeeID to find Name
My logic:
Parameter: Distribution.Name (from C#)
Find DistributionID that has Distribution.Name
Look in Employment WHERE given DistributionID
reveals Employees that I am looking for (BY ID)
Use that ID to find Name
return Name
Tables:
NOTE: In this example picture the Employee repeats because of the select, they are in fact singular
In "Locatie" (middle table) is Location, I get location (again) from C#, I use California as an example. I need to find the ID first and foremost!
Sory they are not in english, but here are the create tables:
Try this:
SELECT angajati.Nume
FROM angajati
JOIN angajari ON angajati.AngajatID = angajari.AngajatID
JOIN distribuire ON angajari.distribuireid = distribuire.distribuireid
WHERE distribuire.locatie = 'california'
As you have a table mapping employees to their distribution locations, you just need to join that one in the middle to create the mapping. You can use variables if you like for the WHERE clause so that you can call this as a stored procedure or whatever you need from the output of your C# code.
Try this solution:
DECLARE #pLocatie VARCHAR(40)='Alba'; -- p=parameter
SELECT a.AngajatID, a.Nume
FROM Angajati a
JOIN Angajari j ON a.AngajatID=j.AngajatID
JOIN Distribuire d ON j.DistribuireID=d.DistribuireID
WHERE d.Locatie=#pLocatie
You should add an unique key on Angajari table (Employment) thus:
ALTER TABLE Angajari
ADD CONSTRAINT IUN_Angajari_AngajatID_DistribuireID UNIQUE (AngajatUD, DistribuireID);
This will prevent duplicated (AngajatID, DistribuireID).
I don't know how you are connecting Emplyee(sic?) and Employment, but you want to use a join to connect two tables and in the join specify how the tables are related. Joins usually look best when they have aliases so you don't have to repeat the entire table name. The following query will get you all the information from both Employment and Distribution tables where the distribution location is equal to california. You can join employee to employment to get name as well.
SELECT *
FROM Employment e
JOIN Distribution d on d.DistributionID = e.DistributionID
WHERE d.Location = 'California'
This will return the contents of both tables. To select particular records use the alias.[Col_Name] separated by a comma in the select statement, like d.DistributionID to return the DistributionID from the Distribution Table