I have two tables, TA and CMI, that contain a person_ID. The ID may exist in TA, it may exist in CMI, or it may exist in both. I want a distinct list of ALL person_ID's regardless whether they are in TA, CMI, or both tables.
I also want to be able to select them where their question_ID's are the same. However, the question_id's have different column names: TA.question and CMI.sco = question_id.
EDIT:
So, if I also wanted to do the select on question as I stated earlier AND a join to the person table, it would look something like:
select ta.person_id, person_key
from ta
left join person on person.person_id = ta.person_id
where question=7033
union -- on purpose to remove duplicates
select cmi.person_id, person_key
from cmi
left join person on person.person_id = cmi.person_id
where sco=7033
You would use union:
select person_id
from ta
union -- on purpose to remove duplicates
select person_id
from cmi;
You can use this as a CTE or subquery in a query.
Related
This one has only one table with three columns student, lect and score. for each lecture I need to find the students who have not got any score.
I have written the below query which uses outer joins, but it can do so only for one lect at a time.
Eg: see below I passed 'L02'
How do I get this working for all the lect values as in (L01,L02,L03...etc)
select distinct * from
(
select distinct Student from import1
where lect ='L02'
)i1
right outer join
(select distinct Student from import1) i2
on i1.Student=i2.Student
where i1.Student is null
output of above is
This works for L02. But, how do I modify above to include for all lect values without hardcoding the values of lect?
Sample data from table:
Need a dataset of all possible student/lecture pairs. If the one table contains all the students and lectures that need to be considered, this dataset can be built with:
SELECT Student, Lect FROM (SELECT DISTINCT Student FROM import1) AS S, (SELECT DISTINCT Lect FROM import1) AS L
Otherwise, need a table of all students and a table of all lectures then query:
SELECT Student, Lect FROM Students, Lectures
Now join that query to the scores table with compound link on both identifier fields and use appropriate filter criteria.
SELECT Query1.Student, Query1.Lect, import1.Score
FROM Query1 LEFT JOIN import1
ON (Query1.Lect = import1.Lect) AND (Query1.Student = import1.Student)
WHERE Score Is Null;
Tested with an Access database.
I have a database with 3 tables; tblCustomers, tblBookings, tblFlights.
I want to find the customer's last name (LName), from the Customers table where the customers do not appear in the bookings table. It should return just three names, but it returns the names 10 times each. There are 10 records in the bookings table, so I think the command is returning the correct names, but not once...
I have tried:
SELECT tblCustomers.LName
FROM tblCustomers, tblBookings
WHERE tblCustomers.CustID
NOT IN (SELECT CustID FROM tblBookings)
How do I return just one instance of the name, not the name repeated 10 times?
You are doing a CROSS JOIN of the 2 tables.
Use only NOT IN:
SELECT LName
FROM tblCustomers
WHERE CustID NOT IN (SELECT CustID FROM tblBookings)
The (implicit) cross join on The bookings table in the outer query makes no sense - and it multiplies the customer rows.
Also, I would recommend not exists for filtering instead of not in: it usually performs better - with the right index in place, and it is null-safe:
SELECT c.LName
FROM tblCustomers c
WHERE NOT EXISTS (SELECT 1 FROM tblBookings b WHERE b.CustID = c.CustID)
For performance, make sure to have an index on tblBookings(CustID) - if you have a proper foreign key declared, it should already be there.
In my mind these 2 sql statements are equivalent.
My understanding is:
the first one i am pulling all rows from tmpPerson and filtering where they do not have an equivalent person id. This query returns 211 records.
The second one says give me all tmpPersons whose id isnt in person. this returns null.
Obviously they are not equivalent or theyd have the same results. so what am i missing? thanks
select p.id, bp.id
From person p
right join(
select distinct id
from tmpPerson
) bp
on p.id= bp.id
where p.id is null
select id
from tmpPerson
where id not in (select id from person)
I pulled some ids from the first result set and found no matching records for them in Person so im guessing the first one is accurate but im still surprised they're different
I much prefer left joins to right joins, so let's write the first query as:
select p.id, bp.id
From (select distinct id
from tmpPerson
) bp left join
person p
on p.id = bp.id
where p.id is null;
(The preference is because the result set keeps all the rows in the first table rather than the last table. When reading the from clause, I immediately know what the first table is.)
The second is:
select id
from tmpPerson
where id not in (select id from person);
These are not equivalent for two reasons. The most likely reason in your case is that you have duplicate ids in tmpPerson. The first version removes the duplicates. The second doesn't. This is easily fixed by putting distincts in the right place.
The more subtle reason has to do with the semantics of not in. If any person.id has a NULL value, then all rows will be filtered out. I don't think that is the case with your query, but it is a difference.
I strongly recommend using not exists instead of not in for the reason just described:
select tp.id
from tmpPerson tp
where not exists (select 1 from person p where p.id = tp.id);
select id
from tmpPerson
where id not in (select id from person)
If there is a null id in tmp person then they will not be captured in this query. But in your first query they will be captured. So using an isnull will be resolve the issue
where isnull(id, 'N') not in (select id from person)
I am trying to get the most frequent Zip_Code for the Location ID from table B. Table A(transaction) has one A.zip_code per Transaction but table B(Location) has multiple Zip_code for one area or City. I am trying to get the most frequent B.Zip_Code for the Account using Location_D that is present in both table.I have simplified my code and changed the names of the columns for easy understanding but this is the logic for my query I have so far.Any help would be appreciated. Thanks in advance.
Select
A.Account_Number,
A.Utility_Type,
A.Sum(usage),
A.Sum(Cost),
A.Zip_Code,
( select B.zip_Code from B where A.Location_ID= B.Location_ID having count(*)= max(count(B.Zip_Code)) as Location_Zip_Code,
A.Transaction_Date
From
Transaction_Table as A Left Join
Location Table as B On A.Location_ID= B.Location_ID
Group By
A.Account_Number,
A.Utility_Type,
A.Zip_Code,
A.Transaction_Date
This is what I come up with:
Select tt.Account_Number, tt.Utility_Type, Sum(tt.usage), Sum(tt.Cost),
tt.Zip_Code,
(select TOP 1 l.zip_Code
Location_Table l
where tt.Location_ID = l.Location_ID
group by l.zip_code
order by count(*) desc
) as Location_Zip_Code,
tt.Transaction_Date
From Transaction_Table tt
Group By tt.Account_Number, tt.Utility_Type, tt.Zip_Code, tt.Transaction_Date;
Notes:
Table aliases are a good thing. However, they should be abbreviations for the tables referenced, rather than arbitrary letters.
The table alias qualifies the column name, not the function. Hence sum(tt.usage) rather than tt.sum(usage).
There is no need for a join in the outer query. You are doing all the work in the subquery.
An order by with top seems the way to go to get the most common zip code (which, incidentally, is called the mode in statistics).
I have a statement like this:
select lastname,firstname,email,floorid
from employee
where locationid=1
and (statusid=1 or statusid=3)
order by floorid,lastname,firstname,email
The problem is the column floorid. The result of this query is showing the id of the floors.
There is this table called floor (has like 30 rows), which has columns id and floornumber. The floorid (in above statement) values match the id of the table floor.
I want the above query to switch the floorid values into the associated values of the floornumber column in the floor table.
Can anyone show me how to do this please?
I am using Microsoft sql server 2008 r2.
I am new to sql and I need a clear and understandable method if possible.
select lastname,
firstname,
email,
floor.floornumber
from employee
inner join floor on floor.id = employee.floorid
where locationid = 1
and (statusid = 1 or statusid = 3)
order by floorid, lastname, firstname, email
You have to do a simple join where you check, if the floorid matches the id of your floor table. Then you use the floornumber of the table floor.
select a.lastname,a.firstname,a.email,b.floornumber
from employee a
join floor b on a.floorid = b.id
where a.locationid=1 and (a.statusid=1 or a.statusid=3)
order by a.floorid,a.lastname,a.firstname,a.email
You need to use a join.
This will join the two tables on a certain field.
This way you can SELECTcolumns from more than one table at the time.
When you join two tables you have to specify on which column you want to join them.
In your example, you'd have to do this:
from employee join floor on employee.floorid = floor.id
Since you are new to SQL you must know a few things. With the other enaswers you have on this question, people use aliases instead of repeating the table name.
from employee a join floor b
means that from now on the table employee will be known as a and the table floor as b. This is really usefull when you have a lot of joins to do.
Now let's say both table have a column name. In your select you have to say from which table you want to pick the column name. If you only write this
SELECT name from Employee a join floor b on a.id = b.id
the compiler won't understand from which table you want to get the column name. You would have to specify it like this :
SELECT Employee.name from Employee a join floor b on a.id = b.id or if you prefer with aliases :
SELECT a.name from Employee a join floor b on a.id = b.id
Finally there are many type of joins.
Inner join ( what you are using because simply typing Join will refer to an inner join.
Left outer join
Right outer join
Self join
...
To should refer to this article about joins to know how to use them correctly.
Hope this helps.