[Okta Webinar] Learn how to a build a cloud-first strategyRegister Now

x
?
Solved

Compound SQL Query

Posted on 2009-05-07
11
Medium Priority
?
567 Views
Last Modified: 2012-05-06
I have constructed this SQL query:
SELECT DISTINCT a.uid, a.sid, a.fname, a.lname, b.class_code from student a, class b where b.grade_code = '2' and a.class = b.class_code and a.school_code = 'SES' order by a.class, a.lname, a.fname

My attempt is to pick up all students in grade 2 for school SES. The grade field is not contained in the student table, rather the class field links to class_code in the class table.

The attached files are (File1), content of table class for all grade 2 classes, (File2) all students who are in grade 2 classes, (File3), partial result.

File4 is the structure of table student. File 5 is the structure of table class.

Note that class 31 in in grade 3, not grade 2.

What's wrong?
File1.jpg
File2.jpg
File3.jpg
File4.jpg
File5.jpg
0
Comment
Question by:Richard Korts
  • 6
  • 3
  • 2
11 Comments
 
LVL 15

Expert Comment

by:DonKronos
ID: 24331276
SELECT DISTINCT a.uid, a.sid, a.fname, a.lname, b.class_code
from student a
inner join class b
on a.class = b.class_code and a.school_code = 'SES' and b.grade_code = '2'
order by a.class, a.lname, a.fname
0
 

Author Comment

by:Richard Korts
ID: 24331445
To DonKronos:

It still picks up students in class 31 (a 3rd grade class).

See attached file (File6)
File6.jpg
0
 
LVL 41

Expert Comment

by:Sharath
ID: 24331616

Can you run this and post the result.
select distinct class_code  
  from class 
 where grade_code = '2' and class_code in (select class from student where school_code = 'SES')

Open in new window

0
What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

 

Author Comment

by:Richard Korts
ID: 24331663
To Sharath_123:

It produces the attached File7 (error).
File7.jpg
0
 
LVL 15

Expert Comment

by:DonKronos
ID: 24331669
Hmmm  ...  doesn't seem logical.

Look in the class table and see what the grade_code is for class_code 31.  I have a suspicion you will find grade_code = 2 for class_code = 31.

If that is not the case then I have to figure out how SQL server is joining rows that do not meet the specified criteria?
0
 

Author Comment

by:Richard Korts
ID: 24331720
To all:

I did what DonKronos suggested (I had already confirmed that before I posted the original question). See attached (File 8).

I have the sinking feeling that it has to do with the fact that the name "class" is used as a column name in the table student and as a table name. I say this because I revised the original DonKronos query to eliminate the aliases & it falid saying something to the effect that "class" was not unique.

I hope I don't have to change the column name, it must be in 30 or 40 php scripts. Or the table name (even worse)
File8.jpg
0
 
LVL 41

Expert Comment

by:Sharath
ID: 24331774

What i am trying to do is to know all the class_codes for school_code = 'SES' and grade_code = '2'
If the class code 31 has the grade_code = '2', then your query will return the records for that class code also.
select class_code  
  from class 
 where grade_code = '2' and class_code in (select class from student where school_code = 'SES')
 group by class_code
 
or
 
select count(class_code)
  from class 
 where grade_code = '2' and class_code in (21,22,31)

Open in new window

0
 
LVL 41

Accepted Solution

by:
Sharath earned 2000 total points
ID: 24331780
pls run this
select class_code
  from class 
 where grade_code = '2' and class_code = 31

Open in new window

0
 

Author Comment

by:Richard Korts
ID: 24331826
To Sharath_123:

I ran this query:

SELECT * from class where school_code = 'SES' and grade_code = '2'.

It produces the arrached File9. This says to me that there are EXACTLY 2 rows in the table that meet this criteria and the row with class_code = 31 is NOT one of them.
File9.jpg
0
 

Author Comment

by:Richard Korts
ID: 24331863
To To Sharath_123:

I ran this query:

Select * from class where class_code = 31 and grade_code = '2". I got the attached. But note that the school_code is NOT 'SES'.

Ah, I think I see the solution. I have to further qualify b (class) that b.school_code = 'SES'. I'll try that.
File10.jpg
0
 

Author Closing Comment

by:Richard Korts
ID: 31579244
The real solution is as I indicated in my last message, I had to add the FURTHER qualification "... and b.school_code = 'SES' ......"

You were most helpful & you led me in the right direction, so you get the points.
0

Featured Post

NFR key for Veeam Backup for Microsoft Office 365

Veeam is happy to provide a free NFR license (for 1 year, up to 10 users). This license allows for the non‑production use of Veeam Backup for Microsoft Office 365 in your home lab without any feature limitations.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Backups and Disaster RecoveryIn this post, we’ll look at strategies for backups and disaster recovery.
The title says it all. Writing any type of PHP Application or API code that provides high throughput, while under a heavy load, seems to be an arcane art form (Black Magic). This article aims to provide some general guidelines for producing this typ…
In this video, Percona Solutions Engineer Barrett Chambers discusses some of the basic syntax differences between MySQL and MongoDB. To learn more check out our webinar on MongoDB administration for MySQL DBA: https://www.percona.com/resources/we…
With just a little bit of  SQL and VBA, many doors open to cool things like synchronize a list box to display data relevant to other information on a form.  If you have never written code or looked at an SQL statement before, no problem! ...  give i…
Suggested Courses

872 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question