I've got a left join query that returns the correct number of rows (equal to the left table), but because the right table is empty, there are no corresponding rowid's. How can I add the rowid (RecNum should be the same value) to the empty table so that I can add data to the resulting dataset? Here's the query:
select
Week01.RecNum as RecNum,
Week01.UserName as UserName,
Week01.Day1Reg as Day1Reg,
Week01.Day1OT as Day1OT,
Week01.Day2Reg as Day2Reg,
Week01.Day2OT as Day2OT,
Week01.Day3Reg as Day3Reg,
Week01.Day3OT as Day3OT,
Week01.Day4Reg as Day4Reg,
Week01.Day4OT as Day4OT,
Week01.Day5Reg as Day5Reg,
Week01.Day5OT as Day5OT,
Week01.Day6Reg as Day6Reg,
Week01.Day6OT as Day6OT,
Week01.Day7Reg as Day7Reg,
Week01.Day7OT as Day7OT
from
"Project List"
left join
Week01
on
"Project List".RecNum = Week01.RecNum
and
Week01.UserName = "JustMe"
or, if that can't really be done, how about a query that will pre-create row entries in Week01 (if they don't already exist) to match the same RecNum column and fill in the username with "JustMe"? But, the thing is that if the RecNum already exists in Week01, it can't be overwritten. Any ideas on that? If that could be done, then the query above should work out just fine.
you can actually select it using IFNULL
SELECT
IFNULL(Week01.RecNum, "Project List".RecNum
..
To answer your question of getting all recNums that exists in project List but not in Week01
you can do use left join
select p.RecNum
from "Project List" p
left join Week01 w
on p.RecNum = w.RecNum
where w.RecNum is NULL
or you can use not exists clause
select p.RecNum
from "Project List" p
where not exists
( select 1 from Week01 w
where p.RecNum = w.RecNum
)
Related
I’m attempting to count records that match specific criteria, including one field being null, but including the null clause results in no records being found.
If I output the contents of the field, it comes back as “(null)”. I’ve tried IS NULL and ISNULL, both of which appear that they should work when looking at other sources, but they both fail for me.
SELECT calls.contact_number, calls.contact_name, COUNT(notes.id) AS note_count
FROM calls LEFT JOIN notes on calls.id = notes.call_id
WHERE calls.contact_number = "123" AND notes.group_id ISNULL
GROUP BY calls.contact_number
This returns no records, whereas I’m expecting it to return one.
Move the condition in the ON clause:
SELECT calls.contact_number, calls.contact_name, COUNT(notes.id) AS note_count
FROM calls LEFT JOIN notes
ON calls.id = notes.call_id AND notes.group_id IS NULL
WHERE calls.contact_number = "123"
GROUP BY calls.contact_number, calls.contact_name
After grabbing a copy of the database, the notes.group_id field was determined to be an integer type, and the record in question actually contained a 0.
The successful query ended up being
SELECT calls.contact_number, calls.contact_name, COUNT(notes.id) as note_count
FROM calls LEFT JOIN notes
ON calls.id = notes.call_id
WHERE calls.contact_number = “123” AND (notes.group_id IS NULL OR notes.group_id = 0)
GROUP BY calls.contact_number
Not sure why the NSLog output of the returned value for group_id was ‘(null)’, some weird conversion?
Edit
I would rather explicitly state my problem I'm facing rather than assuming the approach. There could be an easiest solution to my problem.
I need to select records by joining two different table based on the result from another table. And I have to use different joins based on the result from the first table.
If a particular record is present in the first table, I have two use inner join the first table whereas if it's not present, then I have to left join.
bool recordPresent = select exists (select * from firstTable where access_id = 13) as access
if (recordPresent)
results = select * from secondTable s left join firstTable f on f.access_id = s.access_id where f.access_id is null order by access_id
else
results = select * from secondTable s inner join firstTable f on f.access_id = s.access_id
I have the following columns in a SQLite DB.
id,ts,origin,product,bid,ask,nextts
1,2016-10-18 20:20:54.733,SourceA,Dow,1.09812,1.0982,
2,2016-10-18 20:20:55.093,SourceB,Oil,7010.5,7011.5,
3,2016-10-18 20:20:55.149,SourceA,Dow,18159.0,18161.0,
How can I populate the 'next timestamp' column (nextts) with the next timestamp for the same product (ts), from the same source? I've been trying the following, but I can't seem to put a subquery in an UPDATE statement.
UPDATE TEST a SET nextts = (select ts
from TEST b
where b.id> a.id and a.origin = b.origin and a.product = b.product
order by id asc limit 1);
If I call this, I can display it, but I haven't found a way of updating the value yet.
select a.*,
(select ts
from TEST b
where b.id> a.id and a.origin = b.origin and a.product = b.product
order by id asc limit 1) as nextts
from TEST a
order by origin, a.id;
The problem is that you're using table alias for table in UPDATE statement, which is not allowed. You can skip alias from there and use unaliased (but table-name prefixed) reference to its columns (while keeping aliased references for the SELECT), like this:
UPDATE TEST
SET nextts = (
SELECT b.ts
FROM TEST b
WHERE b.id > TEST.id AND
TEST.origin = b.origin AND
TEST.product = b.product
ORDER BY b.id ASC
LIMIT 1
);
Prefixing unaliased column references with the table name is necessary for SQLite to identify that you're referencing to unaliased table. Otherwise the id column whould be understood as the id from the closest[*] possible data source, in which case it's the aliased table (as b alias), while we're interested in the unaliased table, therefore we need to explicitly tell SQLite that.
[*] Closest data source is the one listed in the same query, or parent query, or parent's parent query, etc. SQLite is looking for the first data source (going from inner part to the outside) in the query hierarchy that defines this column.
I have the following DB structure:
tbl_record(_id,_id_user,...)
tbl_photo(_id,_id_record,...)
tbl_note(_id,_id_record,...)
When listing the records of a specific user while counting the number of photos a record has, I use the following query, which works fine:
SELECT tbl_record._id, COUNT(tbl_photo._id_record) AS photo_count FROM tbl_record
LEFT OUTER JOIN tbl_photo ON tbl_record._id=tbl_photo._id_record
WHERE tbl_record._id_user=? GROUP BY tbl_record._id;
Now, I'd like to do the same as above, but also count the number of notes a record has:
SELECT tbl_record._id, COUNT(tbl_photo._id_record) AS photo_count, COUNT(tbl_note._id_record) AS note_count FROM tbl_record
LEFT OUTER JOIN tbl_photo ON tbl_record._id=tbl_photo._id_record
LEFT OUTER JOIN tbl_note ON tbl_record._id=tbl_note._id_record
WHERE tbl_record._id_user=? GROUP BY tbl_record._id;
The count of the 2nd query does not work properly when a record has >0 photos & >0 notes, e.g. 3 photos & 5 photos which results in a count of 15 (3*5) for each.
Any idea how to make the 2nd query return the proper counts?
Thanks!!
You might be able to filter out duplicates by using COUNT(DISTINCT some_id), but this would be inefficient.
Better use correlated subqueries:
SELECT _id,
(SELECT COUNT(*)
FROM tbl_photo
WHERE _id_record = tbl_record._id
) AS photo_count,
(SELECT COUNT(*)
FROM tbl_note
WHERE _id_record = tbl_record._id
) AS note_count
FROM tbl_record
WHERE _id_user = ?
I have 2 tables, one is indexing the other.
I am querying Table#1, and it has one column (string) that has an ID in it that corresponds to a unique row in Table#2. Im trying to write a query in Sqlite that allows me to retrieve the value from Table#2 if the column value in Table#1 is not an empty string.
Kinda like:
"SELECT TMake,TModel,TTrim,IYear,[%q] AS TPart1 FROM AppGuide WHERE TPart1 != ''"
But instead of retrieving the Index value (TPart1) Id like to get the string from Table#2.
Is this possible?
Any help is appreciated.
You could use a correlated subquery:
SELECT TMake,
TModel,
...,
(SELECT stringvalue
FROM Table2
WHERE Table2.ID = Table1.TPart1)
FROM Table1
WHERE Table1.TPart1 != ''
However, these are rather slow to execute, so you'd better use a join (this returns exactly the same result):
SELECT Table1.TMake,
Table1.TModel,
...,
Table2.stringvalue
FROM Table1 LEFT JOIN Table2 ON Table1.TPart1 = Table2.ID
WHERE Table1.TPart1 != ''
If you don't want to get records from Table1 that have no matching Table2 record, drop the LEFT.