SQL Question
Date: Mon, 28 Jun 1999 03:56:09 GMT
Message-ID: <376edbf2.1228128655_at_gustav>
I'm somewhat new to SQL so please excuse me if this is a silly question. I have a table in my database which contains thousands of records. Each record has one or more fields which hold either a boolean value or a specific text string. I need to be able to compute the percentage of a subset of records which has a particular value set. Currently I do this by making two queries. The first does a count of the records retrieved regardless of the setting of the value that I care about. The second query adds an additional qualifier to test on a field that I'm interested in.
For example, suppose that I had a table of teachers and each record in the table had a field indicating the subject taught by the teacher and the number of years the teacher had taught that subject. I might want to do a query to determine the percentage of Physics teachers who have been teaching the subject for more than 8 years. Currently I would select all records in the table where the subject field was 'Physics' and get a count of the records, something like this:
select count(teacherID) from TeacherTable where subjectTaught='Physics';
I would then do another query to get the teachers who have taught more than 8 years, something like this:
select count(teacherID) from TeacherTable where subjectTaught='Physics' and yearsTaught > 8.
I can then compute the percentage. What I would like to know is if there is a simpler way to get this result. One which doesn't involve making two separate queries. Is there a way to more efficiently compute the result that I'm looking for?
Any help would be appreciated.
Received on Mon Jun 28 1999 - 05:56:09 CEST