SQL: Select table if a column has a given value - mysql

Question

I am new to SQL and programming in general, this could be an easy question, or it may not be, I have not clue. I just know I have not been able to find a straightforward answer. I have an excel file with a bunch of different data sheets. Each data sheet has the same data, just for different occurances. I want to be able to associate certain readings with a given value of the subject. (i.e. I want to be able to return all paces recorded during a race if the person is under 24 years old) In this situation, the paces would be recorded every minutes during a 2 hour race. That would be in a column pace, age would be in another column age. There will be a data sheet for every subject. I ultimately would like to find the average pace of all people in different age ranges (24 and under etc.) I can combine the columns with the UNION command. I am working with SQL in R. What I have looks like this:
sqlQuery(Race, paste("SELECT [PACE] FROM [Bill] UNION [STEVE]"))
I understand the WHERE clause to return rows where the given value is present. My dilemma is I have enough data it would be very time consuming to input the age for every row so that I can query the rows.
Is it possible for me to create code that asks something like "return me all table where age is less than 24?"

Answer 1

I'd strongly advise against putting each data sheet into its own table - just add a column DATA_SHEET to your table to differentiate between occurences.
That said, I'd probably go one step further and use these tables (assuming one data sheet represents one race):
PERSON
------
PK
Name
Age (better: Date of birth, since age changes over time)
Gender
...
RACE
----
PK
Name
Start date
...
PACE
----
PERSON_FK -- foreign key to PERSON table
RACE_FK -- foreign key to race table
PACE
...
This way, to get all paces of people younger than 24 for a given race:
select race.name race_name, person.name person_name, pace.pace
from person, race, pace
where person.pk = pace.person_fk
and race.pk = pace.race_fk
and person.age < 24

Answer 2

sqlQuery(Race, paste("SELECT [PACE], AVG(PACE) FROM [Bill] UNION [STEVE] WHERE columnName["age"] < 24"))
I'm not a master in SQL-server/T-SQL and I have no experience developing R, but in SQL the syntax is not so different from this.
But you could separate the queries like this (I have no clue if the syntax is good):
sqlQuery(Race, paste("SELECT [PACE] FROM [Bill] UNION [STEVE] WHERE [PACE].age < 24"))
then:
sqlQuery(Race, paste("SELECT AVG([PACE].age) FROM [Bill] UNION [STEVE]"))

Answer 3

The question:
Blockquote "return me all table where age is less than 24?"
Implies that you would have more than one table with a column called age. If the age applies to the runner I would suggest reviewing your schema. You should have an entity named something like:
Person
or
Runner
or
Participant
That has a column age. The trick would then be to simply move all your data into that table. Then a simple
SELECT
*
FROM
Person
WHERE
age < 24
Would return all the data you're looking for.
I think where this is getting confusing is the concept of a datasheet in excel vs. a table in SQL. Your data sheets sound like they're instances of a participant with various additional data. Instead of creating a table for each data sheet you should create a schema that fits all of your data and then fill it with each instance from your data.
Take a look here for a reference to schema design:
How to design this RDBMS schema?

Answer 4

Try avg() function of sql server and with where condition where ageCol < 24