I've got 4 tables that I want data from.
Trip_T
tripID (PK)
userID (FK)
...
User_T
userID (PK)
username
...
Excursion_T
excursionID (PK)
tripID (FK)
...
POI_T
poiID (PK)
excursionID (FK)
...
I want to create a table with one row for each trip in the db.
Each row should include the tripID, title, the user's name associated with the trip, the number of excursions made on the the trip and the number of poi (points of interest) associated with those excursions.
I'm using the following query:
SELECT Trip_T.tripID, Trip_T.title, User_T.username
COUNT(DISTINCT Excursion_T.excursionID) AS numExcursions,
COUNT(DISTINCT POI_T.poiID) AS numPOI
FROM Trip_T
INNER JOIN User_T ON User_T.userID = Trip_T.userID
INNER JOIN Excursion_T ON Excursion_T.tripID = Trip_T.tripID
INNER JOIN POI_T ON POI_T.excursionID = Excursion_T.excursionID
Even though I have multiple trips in the db, each with multiple excursions and pois, the query returns 1 row with what looks like the total number of excursions and total number of pois for all trips.
Any help is appreciated.
You forgot to add grouping to your query:
GROUP BY Trip_T.tripID, Trip_T.title, User_T.username
This way the counters correspond to each triplet of (Trip_T.tripID, Trip_T.title, User_T.username)
How do I select by column value count? In SQL query it would be something like this: select * from band inner join bandsinger on band.id = bandsinger.bandid inner join singer on singer.id = bandsinger.singerid group by band.id having count(singerid=6)>0 and count(singerid=4)>0 if SQLite function count() could accept a function as a parameter, but it doesn't.
The point is to select two bands, where two singers with known IDs sing.
I found the solution. In this case a query should be: select * from band inner join bandsinger on band.id = bandsinger.bandid inner join singer on singer.id = bandsinger.singerid where dinger.id = 6 or singer.id=4 group by band.id having count(*)=x where x is number of given IDs to count.
I have two tables. Config and Data. Config table has info to define what I call "Predefined Points". The columns are configId, machineId, iotype, ioid, subfield and predeftype. I have a second table that contains all the data for all the items in the config table linked by configId. Data table contains configId, timestamp, value.
I am trying to return each row from the config table with 2 new columns in the result which would be min timestamp of this particular predefined point and max timestamp of this particular predefined point.
Pseudocode would be
select a.*, min(b.timestamp), max(b.timestamp) from TrendConfig a join TrendData b on a.configId = b.configId where configId = (select configId from TrendConfig)
Where the subquery would return multiple values.
Any idea how to formulate this?
Try an inner join:
select a.*, b.min(timestamp), b.max(timestamp)
from config a
inner join data b
on a.configId = b.configID
I was able to find an answer using: Why can't you mix Aggregate values and Non-Aggregate values in a single SELECT?
The solution was indeed GROUP BY as CL mentioned above.
select a.*, min(b.timestamp), max(b.timestamp) from TrendConfig a join TrendData b on a.configId = b.configId group by a.configId
Can some one please help in solving my problem
I have three tables to be joined ed using indexes in Teradata to improve performance. Query specified below:-
Select b.Id, b.First_name, b.Last_name, c. Id,
c.First_name, c.Last_name, c.Result
from
(
select a.Id, a.First_name, a. Last_name, a.Approver1, a.Approver2
From table1 a
Inner join table2 d
On a.Id =D.Id
and A.Approver1 =a.Approver1
And a.Approve2 =D.Approver2
) b
Left join
(
select * from table3
where result is not null
and application like 'application1'
) c
On c. Id=b.Id
Group by b.Id, b.First_name, b.Last_name, c.Id,
c.First_name, c.Last_name, c.Result
The above query is taking so much of time since PI not defined correctly.
First two tables (table1 and 2) are with same set of columns hence pi can be defined like PI on I'd, approve1, approve2
However, while joining with table3 am confused and need to understand how to define pi. Is it something that PI can only work when we have same set of columns in the tables?
Structure of table3 is
I'd, first name, last name, result
And table 1 and table2
Id , First name, Last name, Approved 1, Approved 2, Results
Can you please help in defining primary indexes so that query can be optimised.
Teradata will usually not use Secondary Indexes for joins. The best PI would be id for all three tables, of course you need to check if there are not too many rows per value and it's not too skewed.
GROUP BY can be simplified to a DISTINCT, why do you need it, can you show the Primary Keys of those tables?
Edit based on comment:
PI-based joins are by far the fastest way. But you should be able the get rid of the DISTINCT, too, it's always a huge overhead.
Try replacing the 1st join with a NOT EXISTS:
Select b.Id, b.First_name, b.Last_name, c. Id,
c.First_name, c.Last_name, c.Result
from
(
select a.Id, a.First_name, a. Last_name, a.Approver1, a.Approver2
From table1 a
WHERE EXISTS
(
SELECT *
FROM table2 d
WHERE a.Id =D.Id
and A.Approver1 =a.Approver1
And a.Approve2 =D.Approver2
)
) b
Left join
(
select * from table3
where result is not null
and application like 'application1'
) c
On c. Id=b.Id
I am trying to update Table B of a database looking like this:
Table A:
id, amount, date, b_id
1,200,6/31/2012,1
2,300,6/31/2012,1
3,400,6/29/2012,2
4,200,6/31/2012,1
5,200,6/31/2012,2
6,200,6/31/2012,1
7,200,6/31/2012,2
8,200,6/31/2012,2
Table B:
id, b_amount, b_date
1,0,0
2,0,0
3,0,0
Now with this query I get all the data I need in one select:
SELECT A.*,B.* FROM A LEFT JOIN B ON B.id=A.b_id WHERE A.b_id>0 GROUP BY B.id
id, amount, date, b_id, id, b_amount, b_date
1,200,6/31/2012,1,1,0,0
3,400,6/29/2012,1,1,0,0
Now, I just want to copy the selected column amount to b_amount and date to b_date
b_amount=amount, b_date=date
resulting in
id, amount, date, b_id, id, b_amount, b_date
1,200,6/31/2012,1,1,200,6/31/2012
3,400,6/29/2012,1,1,400,6/29/2012
I've tried COALESCE() without success.
Does someone experienced have a solution for this?
Solution:
Thanks to the answers below, I managed to come up with this. It is probably not the most efficient way but it is fine for a one time only update. This will insert for you the first corresponding entry of each group.
REPLACE INTO A SELECT id, amount, date FROM
(SELECT A.id, A.amount, B.id as Bid FROM A INNER JOIN B ON (B.id=A.B_id)
ORDER BY A.id DESC)
GROUP BY Bid;
So what you are looking for seems to be a JOIN inside of an UPDATE query. In mySQL you would use
UPDATE B INNER JOIN A ON B.id=A.b_id SET B.amount=A.amount, B.date=A.date;
but this is not supported by sqlite as this probably related question points out. However, there is a workaround using REPLACE:
REPLACE INTO B
SELECT B.id, A.amount, A.date FROM A
LEFT JOIN B ON B.id=A.b_id
WHERE A.b_id>0 GROUP BY B.id;
The query will simply fill in the values of table B for all columns which should keep their state and fill in the values of table A for the copied values. Make sure the order of the columns in the SELECT statement meet your column order of table B and all columns are mentioned or you will loose these field's data. This is probably dangerous for future changes on table B. So keep in mind to change the column order/presence of this query when changing table B.
Something a bit off topic, because you did not ask for that: A.b_id is obviously a foreign key to B.id. It seems you are using the value 0 for the foreign key to express that there is no corresponding entry in B. (Inferred from your SELECT with WHERE A.b_id>0.) You should consider using the null value for that. When you are using INNER JOIN then instead of LEFT JOIN you can drop the WHERE clause entirely. The DBS will then sort out all unsatisfied relations.
WARNING Some RDBMS will return 2 rows as you show above. Others will return the Cartesian product of the rows i.e. A rows times B rows.
One tricky method is to generate SQL that is then executed
SELECT "update B set b.b_amount = ", a.amount, ", b.b_date = ", a.date,
" where b.id = ", a.b_id
FROM A LEFT JOIN B ON B.id=A.b_id WHERE A.b_id>0 GROUP BY B.id
Now add the batch terminator and execute this SQL. The query result should look like this
update B set b.b_amount = 200, b.b_date = 6/31/2012 where b.id = 1
update B set b.b_amount = 400, b.b_date = 6/29/2012 where b.id = 3
NOTE: Some RDBMS will handle dates differently. Some require quotes.