I am using sqlite3 in swift files through the application xcode. I am currently working on a journal project where you log one journal entry a day, and I am storing the contents, date logged etc in a database. Right now I am trying to implement a way to check if a there is already a log existing for a given day. I am using the following query within sqlite3_prepare_v2
IF EXISTS
(
SELECT *
FROM journal
WHERE date = ?)
)
(I am using the ? to later bind a given date btw) How can I check if the evaluation of this query is true or false and set that value to a variable? Will sqlite3_step() return the return values of this query? Thanks!
You can do:
select exists (select 1 from journal where date = ?) as flag
This always gives you a scalar result (one row and one column, called flag), with a 0/1 value that indicates whether at least one record satisfies the condition.
Another option is:
select count(*) > 0 as res
from journal
where date = 1
Related
Evening everyone
I've currently got a simple recycle view adapter which is being populated by an SQL Lite database. The user can add information into the database from the app which then build a row inside of the recycle view. When you run the application it will display each row with its own date directly above it. I'm now looking to make the application look more professional by only displaying a single date above multiple records as a header.
So far I've built 2 custom designs, one which displays the header along with the row and the other which is just a standard row without a header built in. I also understand how to implement two layouts into a single adapter.
I've also incorporated a single row into my database which simply stores the date in a way in which I can order the database e.g. 20190101
Now my key question is when populating the adapter using the information from the SQL Lite database how can get it to check if the previous record has the same date. If the record has the same date then it doesn't need to show the custom row with header but if its a new date then it does?
Thank you
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Follow up question for Krokodilko, I've spent the last hour trying to work your implementation into my SQL Lite but still not being able to find the combination.
below the is the original code SQL Lite line I currently use to simply gain all the results.
Cursor cursor = sqLiteDatabase.rawQuery("SELECT * FROM " + Primary_Table + " " , null);
First you must define an order which will be used to determine which record is previous and which one is next. As I understand, you are simply using date column.
Then the query is simple - use LAG analytic function to pick a column value from previous row, here is a link to a simple demo (click "Run" button):
https://sqliteonline.com/#fiddle-5c323b7a7184cjmyjql6c9jh
DROP TABLE IF EXISTS d;
CREATE TABLE d(
d date
);
insert into d values ( '2012-01-22'),( '2012-01-22'),( '2015-01-22');
SELECT *,
lag( d ) OVER (order by d ) as prev_date,
CASE WHEN d = lag( d ) OVER (order by d )
THEN 'Previous row has the same date'
ELSE 'Previous row has different date'
END as Compare_status
FROM d
ORDER BY d;
In the above demo d column is used in OVER (order by d ) clause to determine the order of rows used by LAG function.
I am trying to automatically count the unique occurrences of a string saved in the table. Currently I have a count of a string but only when a user selects the string and it gives every record the same count value.
For example
Below is a image of my current table:
From the image you can see that there is a Requirement column and a count column. I have got it to the point were when the user would select a requirement record (each requirement record has a link) it would insert the requirement text into a requirement item called 'P33_REQUIREMENT' so the count can have a value to compare to.
This is the SQL that I have at current:
SELECT (SELECT COUNT(*)
FROM DIA_ASSOCIATED_QMS_DOCUMENTS
WHERE REQUIREMENT = :P33_REQUIREMENT
group by REQUIREMENT
) AS COUNT,
DPD.DIA_SELECTED,
DPD.Q_NUMBER_SELECTED,
DPD.SECTION_SELECTED,
DPD.ASSIGNED_TO_PERSON,
DAQD.REFERENCE,
DAQD.REQUIREMENT,
DAQD.PROGRESS,
DAQD.ACTION_DUE_DATE,
DAQD.COMPLETION_DATE,
DAQD.DIA_REF,
DA.DIA,
DA.ORG_RISK_SCORE
FROM DIA_PROPOSED_DETAIL DPD,
DIA_ASSOCIATED_QMS_DOCUMENTS DAQD,
DIA_ASSESSMENTS DA
WHERE DPD.DIA_SELECTED = DAQD.DIA_REF
AND DPD.DIA_SELECTED = DA.DIA
This is the sql used to make the table in the image.
This issue with this is, it is giving every record the same count when the user selects a requirement value. I can kind of fix this by also adding in AND DIA_SELECTED = :P33_DIA into the where clause of the count. DIA_SELECTED being the first column in the table and :P33_DIA being the item that stores the DIA ref number relating to the record chosen.
The output of this looks like:
As you can see there is only one count. Still doesn't fix the entire issue but a bit better.
So to sum up is there a way to have the count, count the occurrences individually and insert them in the requirements that are the same. So if there are three tests like in the images there would be a '3' in the count column where requirement = 'test', and if there is one record with 'test the system' there would be a '1' in the count column.
Also for more context I wont know what the user will input into the requirement so I can't compare to pre-determined strings.
I'm new to stack overflow I am hoping I have explained enough and its not too confusing.
The following extract:
SELECT (SELECT COUNT(*)
FROM DIA_ASSOCIATED_QMS_DOCUMENTS
WHERE REQUIREMENT = :P33_REQUIREMENT group by REQUIREMENT ) AS COUNT
Could be replaced by
SELECT (SELECT COUNT(*)
FROM DIA_ASSOCIATED_QMS_DOCUMENTS
WHERE REQUIREMENT = DAQD.REQUIREMENT ) AS COUNT
Which would give you - for each line, the number of requirements that are identical.
I'm not completely certain it is what you are after, but if it isn't, it should give you some ideas on how to progress (or allow you to indicate where I failed to understand your request)
I am trying to accumulate a value when a certain condition exists such as
If statusCode = 0
then add 1 to a value.
I am trying to show the number of successful records as defined by the statusCode.
There must be a better way to do this.
Thanks
Select count(1) from yourTable where statusCode=0
I have this problem, I've got database table that looks like this:
"63";"CLINICAL...";"Please...";Blah...;"2014-09-23 13:15:59";37;8
"64";"CLINICAL...";"Please...";Blah...;"2014-09-23 13:22:51";37;9
The values that matter are the second to last and last one.
As you can see, the second to last (abstract_category_numbers) are the same, but the last differs (version_numbers)
Here is the problem:
When I make a scope, it returns all of the records, which i need to focus on the one with the maximum version number.
In SQL i would do something like this:
'SELECT * FROM Category c WHERE
NOT EXISTS SELECT * FROM Category c1
WHERE c.version_number < c1.version_number
AND c.abstract_category_id = c1.abstract_category_id'
But i'm totally lost at Ruby, more specifically how to do this kind of select in the scope (I understand it should be a relation)
Thanks
We can create a scope to select the category with max version_number like this:
scope :with_max_version_number, -> {
joins("JOIN ( SELECT abstract_category_id, max(version_number) AS max_version
FROM categories
GROUP BY abstract_category_id
) AS temp
ON temp.abstract_category_id = categories.abstract_category_id
AND temp.max_version = categories.version_number"
)
}
Basically, we will select the category with the max_version value on temp table in the subquery.
Btw, I expect the table name is categories, you may correct it. Then the final query will be:
Category.with_max_version_number
Scopes are suppose to return an array of values even if there is only 1 record.
If you want to ALWAYS return 1 value, use a static method instead.
def self.max_abstract_category
<your_scope>.max_by{ |obj| obj.version_number }
end
If I understand your question: you have a database table with a version_number column, which rails represents using an Active Record model--that I'll call Category because I don't know what you've called it--and you want to find the single Category record with the largest version_number?
Category.all.order(version_numbers: :DESC).limit(1).first
This query asks for all Category records ordered by version_number from highest to lowest and limits the request to one record (the first record, a.k.a the highest). Because the result of this request is an array containing one record, we call .first on the request to simply return the record.
As far as I'm aware, a scope is simply a named query (I don't actually use scopes). I think you can save this query as a scope by adding the following to your Category model. This rails guide explains more about Scopes.
scope :highest_version, -> { all.order(version_numbers: :DESC).limit(1).first }
I join implementation with baby_squeel but for some reason it was very slow on mysql. So I ended up with something like:
scope :only_latest, -> do
where(%{
NOT EXISTS (SELECT * FROM Category c
WHERE categories.version_number < version_number
AND categories.abstract_category_id = abstract_category_id')
}
end
I filed a BabySqueel bug as I spent a long time trying to do in a code proper way to no avail.
I'm attempting to create a SAP UDO for product registrations. The UDO automatically creates two required fields "docentry" and "code." docentry auto-increments, code does not. I don't have accessing to the underlying database structure to fix that, but I can attach a query to the code field.
When a record is created, can I setup a query that would increment based on the previous row's value for code? I'm not looking for anything useful out of this field, but we will need to both batch import .csv files on a regular basis and also take direct submissions from our site, so I'm just looking for the easiest way to make it work.
Thank you.
UPDATE table_name_here SET code = code + 1 WHERE ? = ??
Replace the ? with unique identifier column name and ?? with it's value for row you are working with.
After your comment:
Let's say you have previous row code value stored in $1 and actual row id in $2. Then:
UPDATE registrations SET code = $1 + 1 WHERE id = $2
After your second comment:
UPDATE registrations SET code = (SELECT MAX(code) FROM registrations) + 1 WHERE docentry = `new_row_docentry_value`