[examTableCAtableI want to use mysql cross join between examination tbl & Contineous Assesment tbl with a WHERE clause.
I want to get record of a student from both tables. I try left join exam on CA and it works but the issue is when the student wrote CA but doesn't have exam, his CA will not be counted.
I want to join the two tables so that it can count for student with either exam or CA or both.
This is my left join query:
SELECT examscore.stuid,
examscore.subcode,
examscore.score AS examscore,
csscore.score,
SUM(examscore.score + IFNULL(csscore.score, 0)) AS totalscore
FROM examscore
LEFT JOIN csscore on examscore.stuid = csscore.stuid
and examscore.subcode = csscore.subcode
where examscore.term = 'FIRST'
and examscore.class = 'jss1a'
GROUP BY examscore.stuid;
The above query works only when the student has written the exam.
I try cross join but if i use where clause, it turns to inner join.
Please how can i achieved it.
Thanks
Related
I am trying to join two datasets based on a flag and id.
i.e
proc sql;
create table demo as
select a.*,b.b1,b.2
from table1 a
left join table2 on
(a.flag=b.flag and a.id=b.id) or (a.flag ne b.flag and a.id=b.id)
end;
This code runs into a loop and never produces a output.
I want to make sure that where there are flag values matching get the attributes; if not get the attributes at id level so that we do not have blank values.
This join condition cannot be optimized. It is not a good practice to use or in a join. If you check your log, you'll see this:
NOTE: The execution of this query involves performing one or more Cartesian product joins
that can not be optimized.
Instead, transform your query to do a union:
proc sql;
create table demo as
select a.*,
b.b1,
b.b2
from table1 as a
left join
table2 as b
on a.flag=b.flag and a.id=b.id
UNION
select a.*,
b.b1,
b.b2
from table1 as a
left join
table2 as b
on a.flag ne b.flag and a.id=b.id
;
quit;
Is it possible to join the same table twice?
In our case we want:
polymorphic.left_joins(:course, step: :course)
Problem when polymorphic row has a type "Step" in such case associated course of step does not join
Why do you need to join it twice?
For example we have a Polymorphic model that belongs to either a Course model or a Step model. Step belongs_to course. We should join course or step with course. It means if Polymorphic row has type Course we join course.fields if type Step we need to join steps with course so we can have in one row polymorphic.fields + steps.fields + associated course.fields
⚙ We can join the same table twice manually using alias for table (t1)
⛄
sql = <<-SQL
LEFT JOIN courses
ON courses.id = polymorphicable_id
AND (polymorphicable_type = 'Course')
LEFT JOIN steps
ON steps.id = polymorphicable_id
AND (polymorphicable_type = 'Step')
LEFT JOIN courses AS t1
ON t1.id = steps.course_id
SQL
polymorphic.joins(sql)
I would like to join tables . Could you please help?
Select Number, OwnerId from DNIS.numbers
select ID,Name from DNIS.owners
Thank you.
Normally, SQL servers allow you to join tables from different databases as long as the former all belong to them. Here is an example showing you how to do this (all you have to do is to explicitly write the database names associated to each table in the query):
SELECT N.Number, N.OwnerId, O.ID, O.Name
FROM DB1.[dbo].DNIS numbers N
JOIN DB2.[dbo].DNIS owners O ON O.ID = N.OwnerId
You can also use the following syntax:
SELECT N.Number, N.OwnerId, O.ID, O.Name
FROM DB1..DNIS numbers N
JOIN DB2..DNIS owners O ON O.ID = N.OwnerId
In order to accomplish that you will have to specify the table and column names in your join statement, like so:
SELECT db1.tablename.column, db2.tablename.column
FROM db1.tablename INNER JOIN db2.tablename
ON db1.tablename.id = db2.tablename.id;
Tables Involved:
account, user, service, accesshist
I want to include all records in the account table, and only the data from the other tables when it exists.
Count from account: 5064
rows returned from query below: 4915
select u.last_name, u.first_name, a.username, ll.mxlogin, si.servicename, a.islockedout
from account a
join service si on a.serviceid = si.serviceid
left outer join user u on u.loginid = a.username
left outer join(select max(loginattemptdate) as MxLogin, usernameattempted from accesshist where isloginsuccessful = 1
group by usernameattempted) ll
on a.username = ll.usernameattempted
where a.isenabled = 1
order by ll.mxlogin, u.last_name
I've narrowed it down that the subquery join is the part causing the number of rows to be reduced, but I am unsure how to correct it. Any insight is greatly appreciated!
Have you tried changing the first join to a left outer join?
select u.last_name, u.first_name, a.username, ll.mxlogin, si.servicename, a.islockedout
from account a
left outer join service si on a.serviceid = si.serviceid
I am having to convert code written by a former employee to work in a new database. In doing so I came across some joins I have never seen and do not fully understand how they work or if there is a need for them to be done in this fashion.
The joins look like this:
From Table A
Join(Table B
Join Table C
on B.Field1 = C.Field1)
On A.Field1 = B.Field1
Does this code function differently from something like this:
From Table A
Join Table B
On A.Field1 = B.Field1
Join Table C
On B.Field1 = C.Field1
If there is a difference please explain the purpose of the first set of code.
All of this is done in SQL Server 2012. Thanks in advance for any help you can provide.
I could create a temp table and then join that. But why use up the cycles\RAM on additional storage and indexes if I can just do it on the fly?
I ran across this scenario today in SSRS - a user wanted to see all the Individuals granted access through an AD group. The user was using a cursor and some temp tables to get the users out of AD and then joining the user to each SSRS object (Folders, reports, linked reports) associated with the AD group. I simplified the whole thing with Cross Apply and a sub query.
GroupMembers table
GroupName
UserID
UserName
AccountType
AccountTypeDesc
SSRSOjbects_Permissions table
Path
PathType
RoleName
RoleDesc
Name (AD group name)
The query needs to return each individual in an AD group associated with each report. Basically a Cartesian product of users to reports within a subset of data. The easiest way to do this looks like this:
select
G.GroupName, G.UserID, G.Name, G.AccountType, G.AccountTypeDesc,
[Path], PathType, RoleName, RoleDesc
from
GroupMembers G
cross apply
(select
[Path], PathType, RoleName, RoleDesc
from
SSRSOjbects_Permissions
where
Name = G.GroupName) S;
You could achieve this with a temp table and some outer joins, but why waste system resources?
I saw this kind of joins - it's MS Access style for handling multi-table joins. In MS Access you need to nest each subsequent join statement into its level brackets. So, for example this T-SQL join:
SELECT a.columna, b.columnb, c.columnc
FROM tablea AS a
LEFT JOIN tableb AS b ON a.id = b.id
LEFT JOIN tablec AS c ON a.id = c.id
you should convert to this:
SELECT a.columna, b.columnb, c.columnc
FROM ((tablea AS a) LEFT JOIN tableb AS b ON a.id = b.id) LEFT JOIN tablec AS c ON a.id = c.id
So, yes, I believe you are right in your assumption