I have a table "channel".
channelId
a
b
c
d
a table "video"
videoId | channelId
1 | a
2 | b
3 | c
4 | e
a table "comment"
commentID | videoID | videoID_channelID
xx | 1 | a
yy | 2 | b
zz | 5 | e
tt | 6 | f
Keys are:
channel.channelId = video.channelId = comment.videoID_channelID
video.videoId = comment.videoID
I need:
all channels with at least 1 video and 1 comment
all videos with at least 1 channel and 1 comment
all comments with a video and a channel
So I want to do 3 SQL statements, one for each table that references the other 2.
I tried it with a double inner-join (https://www.sqlitetutorial.net/sqlite-inner-join/) but it seems to return all combinations that fit rather than:
channelId
a
b
videoId | channelId
1 | a
2 | b
commentID | videoID | videoID_channelID
xx | 1 | a
yy | 2 | b
My code so far to get all channels with at least 1 video and 1 comment:
SELECT
channel.channelId
FROM
channel
INNER JOIN video ON video.channelId = channel.channelId
INNER JOIN comment ON comment.videoID_channelID = video.channelId
You can get all the results that you want with the same query that joins all 3 tables, but for each case select different columns:
SELECT c.channelId
FROM channel c
INNER JOIN video v ON v.channelId = c.channelId
INNER JOIN comment cm ON cm.videoID_channelID = v.channelId;
SELECT v.videoID, c.channelId
FROM channel c
INNER JOIN video v ON v.channelId = c.channelId
INNER JOIN comment cm ON cm.videoID_channelID = v.channelId;
SELECT cm.commentID, v.videoID, c.channelId
FROM channel c
INNER JOIN video v ON v.channelId = c.channelId
INNER JOIN comment cm ON cm.videoID_channelID = v.channelId;
You may have to add DISTINCT after each SELECT if you get duplicates in your actual data.
See the demo.
Results:
| channelId |
| --------- |
| a |
| b |
| videoID | channelId |
| ------- | --------- |
| 1 | a |
| 2 | b |
| commentID | videoID | channelId |
| --------- | ------- | --------- |
| xx | 1 | a |
| yy | 2 | b |
Related
I am building a chat application where I am using Firebase to send and receive messages. Once I send or receive a message, I am storing it to SQLite as follows. Now it the recent chats screen, I need the last message from all the unique chats, number of unread messages in those unique chats in one single query as I am observing the SQLite database.
Mid(STRING) | SentBy | SentTo | message | readTime | sentTime| Type
----------------+--------+--------+---------+----------+---------+------
A | AA | JD | M1 | 1 | 0 | S
B | JD | AA | M2 | 2 | 1 | s
C | AA | JD | M3 | 3 | 2 | s
D | AB | JD | m5 | null | 3 | s
E | AA | JC | M1 | 5 | 4 | s
F | JD | AB | M2 | 6 | 5 | s
G | AA | JD | M3 | 7 | 6 | s
H | AA | JC | m5 | 8 | 7 | s
I | AA | JD | M1 | null | 8 | s
J | JD | AA | M2 | 10 | 9 | s
K | AA | JD | M3 | 11 | 10 | s
L | AB | JC | m5 | 12 | 11 | s
M | AA | JD | M1 | 13 | 12 | s
N | JC | AA | M2 | 14 | 13 | s
O | AB | JD | M3 | 15 | 14 | s
P | JC | JD | m5 | 16 | 15 | s
I tried
SELECT *,COUNT() FROM messagesTable GROUP BY min ( sentBy, sentTo ), max( sentBy , sentTo ) ORDER BY sentTime desc
This query gives me the last messages from every combination of sentTo and sentBy. But I also need to know how many messages are unread for that combination. I want to run a query for every row like
SELECT COUNT() FROM messagesTable WHERE sentBy = message.sentBy, sentTo = message.sentTo, readTime = null
How can I run both queries in a single query?
You must group by the combination of (sentby, sentto) and with a straight count(*) get the total number of messages and with conditional aggregation you can get the number of unread mesages.
Then join to the result to the table to get also the last message:
select
g.user1, g.user2, g.lasttime, m.message lastmessage,
g.totalcounter, g.unreadcounter
from messagestable m inner join (
select
min(sentby, sentto) user1, max(sentby, sentto) user2,
max(senttime) lasttime, count(*) totalcounter,
sum(case when readtime is null then 1 else 0 end) unreadcounter
from messagestable
group by user1, user2
) g
on g.user1 = min(m.sentby, m.sentto) and g.user2 = max(m.sentby, m.sentto)
and g.lasttime = m.senttime
order by g.lasttime desc
See the demo.
Results:
| user1 | user2 | lasttime | lastmessage | totalcounter | unreadcounter |
| ----- | ----- | -------- | ----------- | ------------ | ------------- |
| JC | JD | 15 | m5 | 1 | 0 |
| AB | JD | 14 | M3 | 3 | 1 |
| AA | JC | 13 | M2 | 3 | 0 |
| AA | JD | 12 | M1 | 8 | 1 |
| AB | JC | 11 | m5 | 1 | 0 |
It seems MonetDB does not support recursive CTE. This is a useful feature that I used to get BOM from ERP systems. For a greater flexibility I used Firebird recursive stored procedures to enhance the output with extra calculations. A good example of SQLServer recursive CTE can be found here https://www.essentialsql.com/recursive-ctes-explained/
Question is: Is it any way I can achieve similar results in MonetDB?
There is currently no support for recursive CTEs in MonetDB[Lite]. The solution you have proposed yourself seems like the way to go.
It is clear that once I have access to procedures, variables and while-loop, something can be done. The following code provides me the desired result using temporary tables. I would appreciate if anybody can provide me an alternative to this solution that provides the same results without using the temporary tables overhead.
CREATE TEMPORARY TABLE BOM (parent_id string, comp_id string, qty double) ON COMMIT PRESERVE ROWS;
INSERT INTO BOM VALUES('a','b',5), ('a','c',2), ('b','d',4), ('b','c',7), ('c','e',3);
select * from BOM;
+-----------+---------+--------------------------+
| parent_id | comp_id | qty |
+===========+=========+==========================+
| a | b | 5 |
| a | c | 2 |
| b | d | 4 |
| b | c | 7 |
| c | e | 3 |
+-----------+---------+--------------------------+
CREATE TEMPORARY TABLE EXPLODED_BOM (parent_id string, comp_id string, path string, qty double, level integer) ON COMMIT PRESERVE ROWS;
CREATE OR REPLACE PROCEDURE UPDATE_BOM()
BEGIN
DECLARE prev_count int;
DECLARE crt_count int;
DECLARE crt_level int;
delete from EXPLODED_BOM; --make sure is empty
insert into EXPLODED_BOM select parent_id, comp_id, parent_id||'-'||comp_id, qty, 0 from BOM; --insert first level
SET prev_count = 0;
SET crt_count = (select count(*) from EXPLODED_BOM);
SET crt_level = 0;
-- (crt_level < 100) avoids possible infinite loop, if BOM is malformed
WHILE (crt_level < 100) and (crt_count > prev_count) DO
SET prev_count = crt_count;
insert into EXPLODED_BOM select e.parent_id, a.comp_id, e.path||'-'||a.comp_id, a.qty*e.qty, crt_level+1
from BOM a, EXPLODED_BOM e
where a.parent_id = e.comp_id and e.level=crt_level;
-- is it any chance to get the amount of "affected rows" by insert, update or delete statements, this way I can avoid checking the new count?
SET crt_count = (select count(*) from EXPLODED_BOM);
SET crt_level = crt_level +1;
END WHILE;
END;
call UPDATE_BOM();
select * from EXPLODED_BOM;
+-----------+---------+---------+--------------------------+-------+
| parent_id | comp_id | path | qty | level |
+===========+=========+=========+==========================+=======+
| a | b | a-b | 5 | 0 |
| a | c | a-c | 2 | 0 |
| b | d | b-d | 4 | 0 |
| b | c | b-c | 7 | 0 |
| c | e | c-e | 3 | 0 |
| a | d | a-b-d | 20 | 1 |
| a | c | a-b-c | 35 | 1 |
| a | e | a-c-e | 6 | 1 |
| b | e | b-c-e | 21 | 1 |
| a | e | a-b-c-e | 105 | 2 |
+-----------+---------+---------+--------------------------+-------+
I am trying to update Data1's ID to Record2's ID when:
Record1's and Record2's Name are the same, and
Weight is greater in Record2.
Record1
| ID | Weight | Name |
|----|--------|------|
| 1 | 10 | a |
| 2 | 10 | b |
| 3 | 10 | c |
Record2
| ID | Weight | Name |
|----|--------|------|
| 4 | 20 | a |
| 5 | 20 | b |
| 6 | 20 | c |
Data1
| ID | Weight |
|----|--------|
| 4 | 40 |
| 5 | 40 |
I have tried the following SQLite query:
update data1
set id =
(select record2.id
from record2,record1
where record1.name=record2.name
and record1.weight<record2.weight)
where id in
(select record1.id
from record1, record2
where record1.name=record2.name
and record1.weight<record2.weight)
Using the above query Data1's id is updated to 4 for all records.
NOTE: Record1's ID is the foreign key for Data1.
For the given data set the following seems to serve the cause:
update data1
set id =
(select record2.id
from record2,record1
where
data1.id = record1.id
and record1.name=record2.name
and record1.weight<record2.weight)
where id in
(select record1.id
from record1, record2
where
record1.id in (select id from data1)
and record1.name=record2.name
and record1.weight<record2.weight)
;
See it in action: SQL Fiddle.
Please comment if and as this requires adjustment / further detail.
I have 2 tables, reservations and articles:
Reservations
------------------------------
Id | Name | City |
------------------------------
1 | Mike | Stockholm
2 | Daniel | Gothenburg
2 | Daniel | Gothenburg
3 | Andre | Gothenburg (Majorna)
Articles
-------------------------------------------------------------
ArticleId | Name | Amount | ReservationId |
-------------------------------------------------------------
10 | Coconuts | 1 | 1
10 | Coconuts | 4 | 2
11 | Apples | 2 | 2
12 | Oranges | 2 | 3
I want to select Articles Name and the sum of Articles.Amount per Articles.ArticleId and Reservations.City.
My code:
SELECT distinct r.ID,a.Name as ArticleName,
sum(a.Amount) as ArticlesAmount,
substr(r.City,1,3) as ToCityName
FROM Reservations r
INNER JOIN Articles a
on r.Id = a.ReservationId
WHERE a.Name <> ''
GROUP BY ToCityName,a.ArticleId,a.Name
ORDER BY ToCityName ASC
This gives me following result:
Id | ArticleName | ArticlesAmount | ToCityName
2 | Coconuts | 8 | Got
2 | Apples | 4 | Got
3 | Oranges | 2 | Got
1 | Coconuts | 1 | Sto
But i want:
Id | ArticleName | ArticlesAmount | ToCityName
2 | Coconuts | 4 | Got
2 | Apples | 2 | Got
3 | Oranges | 2 | Got
1 | Coconuts | 1 | Sto
Help would be appreciated, and an explanation please :)
Fiddle
Have a look at SQLFiddle
Code:
SELECT distinct r.ID,a.Name as ArticleName,
sum(distinct a.Amount) as ArticlesAmount,
substr(r.City,1,3) as ToCityName
FROM Reservations r
INNER JOIN Articles a
on r.Id = a.ReservationId
WHERE a.Name <> ''
GROUP BY ToCityName,a.ArticleId,a.Name
ORDER BY ToCityName ASC
You want to ensure you sum the amount by the distinct number of times it appears per group.
I had added Articles again to select requested rows again... here is query
SELECT DISTINCT
r.ID,
a.`Name` AS ArticleName,
Articles.Amount,
substr(r.City, 1, 3) AS ToCityName
FROM
Reservations r
INNER JOIN Articles a ON r.Id = a.ReservationId
INNER JOIN Articles ON a.ReservationId = Articles.ReservationId
AND a.ArticleId = Articles.ArticleId
WHERE
a. NAME <> ''
GROUP BY
ToCityName,
a.ArticleId,
a. NAME
ORDER BY
ToCityName ASC
I have 3 sqlite tables:
table inspections, where insp_id is primary key
id | name | deleted
------------------------------
I1 | Inspection A | (null)
I2 | Inspection B | (null)
I3 | Inspection C | 1
table equip_insp, where equip_id, insp_id are primary keys
equip_id | insp_id | period | period_type
--------------------------------------------
E1 | I1 | 1 | Y
E1 | I2 | 6 | M
E2 | I1 | 1 | M
table equip_certif, where id is primary key
id | equip_id | insp_id | date | certif_no | result | info
-------------------------------------------------------------------
C4 | E1 | I1 | 2015-02-01 | A-300 | Good | (null)
C3 | E1 | I1 | 2015-02-01 | A-200 | Good | (null)
C2 | E1 | I1 | 2015-01-10 | A-100 | Good | (null)
C1 | E1 | I2 | 2015-01-06 | B-100 | Good | (null)
All ID's are in fact numeric values, I use some letters just to be easy to connect them in between.
So, I would like help me with the Sqlite syntax that for item E1, display all the inspection defined (ascending), then if exist, to display the periodicity and then to display the latest certificate date (if there are 2 certificates in the same date, get the latest id), number and result that is not info
Result should be something like this:
id | name | period | period_type | certif_no | date | result
--------------------------------------------------------------------------
I1 | Inspection A | 1 | Y | A-300 | 2015-02-01 | Good
I2 | Inspection B | 6 | M | B-100 | 2015-01-06 | Good
I've try this, but I'm not so sure that is correct.
SELECT inspections.id, inspections.name, equip_insp.period, equip_insp.period_type, equip_certif.certif_no, equip_certif.date AS certif_date, equip_certif.result
FROM inspections
LEFT JOIN equip_insp ON (inspections.id = equip_insp.insp_id AND equip_insp.equip_id = 'E1')
LEFT JOIN equip_certif ON (inspections.id = equip_certif.insp_id AND equip_certif.info IS NULL)
WHERE inspections.deleted IS NULL
GROUP BY equip_insp.insp_id
ORDER BY inspections.id, date(equip_certif.date) DESC, equip_certif.id DESC
To specifiy which row from a group gets returned, you must use MAX(); otherwise, you get some randrom row:
SELECT ..., MAX(equip_certif.date) AS certif_date, ...
FROM ...
GROUP BY equip_insp.insp_id
...
(This works only in SQLite 3.7.11 or later; in earlier version, the query would get more complex.)
After playing with SQLite I get the solution by myself. So the answer is:
SELECT inspections.id, inspections.name, equip_insp.period, equip_insp.period_type, equip_certif.certif_no, equip_certif.date AS certif_date, equip_certif.result
FROM inspections
LEFT JOIN equip_insp ON (inspections.id = equip_insp.insp_id AND equip_insp.equip_id = 'E1')
LEFT JOIN equip_certif ON (inspections.id = equip_certif.insp_id AND equip_certif.equip_id = equip_insp.equip_id AND equip_certif.info IS NULL)
WHERE inspections.deleted IS NULL
GROUP BY inspections.id
ORDER BY inspections.id, date(equip_certif.date) DESC, equip_certif.id DESC