I have a table looking something like this:
+-------+-----+
|country|prop1|
+-------+-----+
|RO | 1 |
|RO | 2 |
|UK | 1 |
|IT | 2 |
+-------+-----+
I want to count the rows for which the prop1 is not null and I use the following select:
SELECT `country`, COUNT(*) as number FROM table GROUP BY `country`;
this will return:
+-------+------+
|country|number|
+-------+------+
|RO | 2 |
|UK | 1 |
|IT | 1 |
+-------+------+
however I need the following:
+-------+------+
|country|number|
+-------+------+
|RO | 2 |
|UK | 1 |
|IT | 1 |
|FR | 0 |
+-------+------+
Do you think something like this can be possible to write directly in SQL? I was thinking something like specifying list of possible values for "country" and a default value (0) if it is not found in the table.
It's not obvious in your example where the FR comes from.
MySQL does not have a list of countries inside it, so country codes should be taken from somewhere.
If you have all countries inside mytable (with prop possibly set to NULL):
SELECT country, COUNT(prop) as number
FROM mytable
GROUP BY
country
If you have countries in a separate table (and a country may be missing in mytable):
SELECT c.id, COUNT(m.prop) as number
FROM countries c
LEFT JOIN
mytable m
ON m.country = c.id
GROUP BY
c.id
I think you will have to set up a table with all the countries. It will be best to alter your current table to use the keys of the countries. So that you can do a LEFT JOIN. That will give you all the countries, with NULL values if there are no props for that country.
Related
I want to join tables in MS Access in such a way that it fetches only the latest record from one of the tables. I've looked at the other solutions available on the site, but discovered that they only work for other versions of SQL. Here is a simplified version of my data:
PatientInfo Table:
+-----+------+
| ID | Name |
+-----+------+
| 1 | John |
| 2 | Tom |
| 3 | Anna |
+-----+------+
Appointments Table
+----+-----------+
| ID | Date |
+----+-----------+
| 1 | 5/5/2001 |
| 1 | 10/5/2012 |
| 1 | 4/20/2018 |
| 2 | 4/5/1999 |
| 2 | 8/8/2010 |
| 2 | 4/9/1982 |
| 3 | 7/3/1997 |
| 3 | 6/4/2015 |
| 3 | 3/4/2017 |
+----+-----------+
And here is a simplified version of the results that I need after the join:
+----+------+------------+
| ID | Name | Date |
+----+------+------------+
| 1 | John | 4/20/2018 |
| 2 | Tom | 8/8/2010 |
| 3 | Anna | 3/4/2017 |
+----+------+------------+
Thanks in advance for reading and for your help.
You can use aggregation and JOIN:
select pi.id, pi.name, max(a.date)
from appointments as a inner join
patientinfo as pi
on a.id = pi.id
group by pi.id, pi.name;
something like this:
select P.ID, P.name, max(A.Date) as Dt
from PatientInfo P inner join Appointments A
on P.ID=A.ID
group by P.ID, P.name
Both Bing and Gordon's answers work if your summary table only needs one field (the Max(Date)) but gets more tricky if you also want to report other fields from the joined table, since you would need to include them either as an aggregated field or group by them as well.
Eg if you want your summary to also include the assessment they were given at their last appointment, GROUP BY is not the way to go.
A more versatile structure may be something like
SELECT Patient.ID, Patient.Name, Appointment.Date, Appointment.Assessment
FROM Patient INNER JOIN Appointment ON Patient.ID=Appointment.ID
WHERE Appointment.Date = (SELECT Max(Appointment.Date) FROM Appointment WHERE Appointment.ID = Patient.ID)
;
As an aside, you may want to think whether you should use a field named 'ID' to refer to the ID of another table (in this case, the Apppintment.ID field refers to the Patient.ID). You may make your db more readable if you leave the 'ID' field as an identifier specific to that table and refer to that field in other tables as OtherTableID or similar, ie PatientID in this case. Or go all the way and include the name of the actual table in its own ID field.
Edited after comment:
Not quite sure why it would crash. I just ran an equivalent query on 2 tables I have which are about 10,000 records each and it was pretty instanteneous. Are your ID fields (i) unique numbers and (ii) indexed?
Another structure which should do the same thing (adapted for your field names and assuming that there is an ID field in Appointments which is unique) would be something like:
SELECT PatientInfo.UID, PatientInfo.Name, Appointments.StartDateTime, Appointments.Assessment
FROM PatientInfo INNER JOIN Appointments ON PatientInfo_UID = Appointments.PatientFID
WHERE Appointments.ID = (SELECT TOP 1 ID FROM Appointments WHERE Appointments.PatientFID = PatientInfo_UID ORDER BY StartDateTime DESC)
;
But that is starting to look a bit contrived. On my data they both produce the same result (as they should!) and are both almost instantaneous.
Always difficult to troubleshoot Access when it crashes - I guess you see no error codes or similar? Is this against a native .accdb database or another server?
I was looking to provide an answer to this question in which the OP has two tables:
Table1
+--------+--------+
| testID | Status |
+--------+--------+
| 1 | |
| 2 | |
| 3 | |
+--------+--------+
Table2
+----+--------+--------+--------+
| ID | testID | stepID | status |
+----+--------+--------+--------+
| 1 | 1 | 1 | pass |
| 2 | 1 | 2 | fail |
| 3 | 1 | 3 | pass |
| 4 | 2 | 1 | pass |
| 5 | 2 | 2 | pass |
| 6 | 3 | 1 | fail |
+----+--------+--------+--------+
Here, the OP is looking to update the status field for each testID in Table1 with pass if the status of all stepID records associated with the testID in Table2 have a status of pass, else Table1 should be updated with fail for that testID.
In this example, the result should be:
+--------+--------+
| testID | Status |
+--------+--------+
| 1 | fail |
| 2 | pass |
| 3 | fail |
+--------+--------+
I wrote the following SQL code in an effort to accomplish this:
update Table1 a inner join
(
select
b.testID,
iif(min(b.status)=max(b.status) and min(b.status)='pass','pass','fail') as v
from Table2 b
group by b.testID
) c on a.testID = c.testID
set a.testStatus = c.v
However, MS Access reports the all-too-familiar, 'operation must use an updateable query' response.
I know that a query is not updateable if there is a one-to-many relationship between the record being updated and the set of values, but in this case, the aggregated subquery would yield a one-to-one relationship between the two testID fields.
Which left me asking, why is this query not updateable?
You're joining in a query with an aggregate (Max).
Aggregates are not updateable. In Access, in an update query, every part of the query has to be updateable (with the exception of simple expressions, and subqueries in WHERE part of your query), which means your query is not updateable.
You can work around this by using domain aggregates (DMin and DMax) instead of real ones, but this query will take a large performance hit if you do.
You can also work around it by rewriting your aggregates to take place in an EXISTS or NOT EXISTS clause, since that's part of the WHERE clause thus doesn't need to be updateable. That would likely minimally affect performance, but means you have to split this query in two: 1 query to set all the fields to "pass" that meet your condition, another to set them to "fail" if they don't.
I want to create a new table using the results from some queries. I might be looking at this the wrong way so please feel free to let me know. Because of this I will try to make this question simple without putting my code to match each employee number with each manager level column from table2
I have two tables, one has employee names and employee numbers example
table 1
+-------------+-----------+-------------+-------------+
| emplpyeenum | firstname | last name | location |
+-------------+-----------+-------------+-------------+
| 11 | joe | free | JE |
| 22 | jill | yoyo | XX |
| 33 | yoda | null | 9U |
+-------------+-----------+-------------+-------------+
and another table with employee numbers under each manager level so basically a hierarchy example
Table 2
+---------+----------+----------+
| manager | manager2 | manager3 |
+---------+----------+----------+
| 11 | 22 | 33 |
+---------+----------+----------+
I want to make a new table that will have the names besides the numbers, so for example but with employee number beside the names
+---------+--------+----------+
| level 1 | level2 | level3 |
+---------+--------+----------+
| jill | joe | yoda |
+---------+--------+----------+
How can I do this?
edit sorry guys I don't have permission to create a new table or view
Why not change your table2 to this?
+------------+----------+
| EmployeeId | ManagerId|
+------------+----------+
| 11 | NULL |
+------------+----------+
| 22 | 11 |
+------------+----------+
| 33 | 22 |
+------------+----------+
Then you can do what you want with the data. At least your data will be properly normalized. In your table2. What happen if employee 33 hire another employee below him? You will add another column?
Based on your available table, this should give you the result you want.
SELECT m1.firstname, m2.firstname, m3.firstname
FROM table2 t
LEFT JOIN table1 m1 ON m1.employeenum = t.manager
LEFT JOIN table1 m2 ON m2.employeenum = t.manager2
LEFT JOIN table1 m3 ON m3.employeenum = t.manager3
You can just do a basic create table, then do a insert select to that will fill the table the way you need it. All you have to do is replace the select statement that I provided with the one you used to create the levels table output.
create table Levels
(
level1 varchar(25),
level2 varchar(25),
level3 varchar(25)
)
insert into Levels(level1, level2, level3)
select * from tables --here you would put the select statement that you used to create the information. If you dont have this script then let me know
I need to link two tables columns, please help me. This my code:
SELECT Student.Stu_Course_ID, Course.Course_Name, COUNT(Student.Stu_ID) AS NoOfStudent FROM Student
INNER JOIN Course
ON Student.Stu_Course_ID=Course.Course_ID
GROUP BY Stu_Course_ID;
This is my course table:
__________________________________________
|Course_ID | Course_Name |
|1 | B.Eng in Software Engineering |
|2 | M.Eng in Software Engineering |
|3 | BSC in Business IT |
I got number of students from student table
_____________________________
|Stu_Course_ID | NoOfStudents |
|1 | 30 |
|2 | 12 |
|3 | 20 |
This is what i want
____________________________________________________________
|Stu_Course_ID | Course_Name | NoOfStudents|
|1 | B.Eng in Software Engineering | 30 |
|2 | M.Eng in Software Engineering | 12 |
|3 | BSC in Business IT | 20 |
You need to add Course.Course_Name to your group by clause:
SELECT Student.Stu_Course_ID,
Course.Course_Name,
COUNT(Student.Stu_ID) AS NoOfStudent
FROM Student
INNER JOIN Course
ON Student.Stu_Course_ID=Course.Course_ID
GROUP BY Student.Stu_Course_ID, Course.Course_Name;
Imagine the following simple table (T):
ID | Column1 | Column2 |
----|---------+----------|
1 | A | X |
2 | A | Y |
Your query is similary to this:
SELECT ID, Column1, COUNT(*) AS Count
FROM T
GROUP BY Column1;
So, you know you have 2 records for A in column1, so you expect a count of 2, however, you are also selecting ID, there are two different values for ID where Column1 = A, so the following result:
ID | Column1 | Count |
----|---------+----------|
1 | A | 2 |
Is no more or less correct than
ID | Column1 | Count |
----|---------+----------|
2 | A | 2 |
This is why ID cannot be contained in the select list, unless it included in the group by clause, or as part of an aggregate function.
For what it's worth, if Course_ID is the primary key in the table Course then following query is legal according to the SQL Standard, and will work in Postgresql, and I suspect at some point Microsoft will build this functionality into SQL Server too:
SELECT Course.Course_ID,
Course.Course_Name,
COUNT(Student.Stu_ID) AS NoOfStudent
FROM Student
INNER JOIN Course
ON Student.Stu_Course_ID=Course.Course_ID
GROUP BY Course.Course_ID;
The reason for this is that since Course.Course_ID is the primary key of Course there can be no duplicates of this in the table, therefore there can only be one value for Course_name for each Course_ID
give columns names after group by statements which you want to retreive so you have to also give Course.Course_Name as well...
Alright well I recently got into normalizing my database for this little side project that I have been creating for a while now, but I've just hit a brick wall. I'll try to give an understandable example of what I have and what I need to accomplish ― and hopefully it won't be too painful. OK.
I have 3 tables the first one we will call Shows, structured something like this:
+----+--------------------------+
| id | title |
+----+--------------------------+
| 1 | Example #1 |
| 2 | Example #2 |
| 3 | Example #3 |
+----+--------------------------+
Plain and simple.
My next table is called Categories, and lookes like this:
+----+--------------------------+
| id | category |
+----+--------------------------+
| 1 | Comedy |
| 2 | Drama |
| 3 | Action |
+----+--------------------------+
And a final table called Show_categories:
+---------+---------+
| show_id | cat_id |
+---------+---------+
| 1 | 1 |
| 1 | 3 |
| 2 | 2 |
| 2 | 3 |
| 3 | 1 |
| 3 | 2 |
+---------+---------+
As you may have noticed the problem is the in my database a single show can have multiple categories. Everything is structured fine, except for the fact that I can't find a why to search for show with multiple categories.
If I were to search for action and comedy type shows I would be given Example #1, but it is not possible (at least with my queries), because the cat_id's inside the Show_categories are in different rows.
Example of a working single category search (Selecting all comedy shows):
SELECT s.id,s.title
FROM Shows s JOIN Show_categories sc ON sc.anid=s.id
WHERE sc.cat_id=1 GROUP BY s.id
And a query that is impossible (because cat_id can't equal 2 different things):
SELECT s.id,s.title
FROM Shows s JOIN Show_categories sc ON sc.anid=s.id
WHERE sc.cat_id=1 AND sc.cat_id=2 GROUP BY s.id
So to sum things up what I am asking is how do I handle a query where I am looking for a show based on multiple matching categories.
Use:
SELECT s.id,
s.title
FROM SHOWS s
JOIN SHOW_CATEGORIES sc ON sc.anid = s.id
WHERE sc.cat_id IN (1, 2)
GROUP BY s.id, s.title
HAVING COUNT(DISTINCT sc.cat_id) = 2
The COUNT(DISTINCT sc.cat_id) comparison needs to equal the number of cat_id values listed in the IN clause. But if both the SHOW_CATEGORIES show_id and cat_id columns are either the primary key, or there's a unique constraint on both columns -- then you can use COUNT(sc.cat_id).
You need an OR statement.
SELECT s.id,s.title
FROM Shows s JOIN Show_categories sc ON sc.anid=s.id
WHERE sc.cat_id=1 OR sc.cat_id=2 GROUP BY s.id
That is, you want all shows with either catid 1 OR catid 2. So this query will return 1, 2 and 3.