I have a SQL table called contacts which as n number of rows where n is more than 10Lakh (1 million) rows.
Below is the table structure with dummy data
+---------------+------------+---------+-----------+---------+------------------------+
| email | department | title | state | country | cleansing_verification |
+---------------+------------+---------+-----------+---------+------------------------+
| xyz#email.com | h.r. | sr. Exe | telangana | Ind | - |
+---------------+------------+---------+-----------+---------+------------------------+
So, I have 4 schedulers to cleanse the data which is present in the above table, ie
department cleanser
title cleanser
state cleanser
country cleanser
Each cleanser will update the data of the respective columns. I have added one more column call cleansing_verification to identify which column is updated but not able to use properly.
One email can be touched by any of the cleansers. Which means all 4 can update the value or any 3 or any 2 or only 1.
So, the problem is I'm facing is How to identify which email is touched and which is not so that for remaining I can send an email notification.
If something more need let me know I will add in the question.
Thanks in advance.
So normally we don't do this in the world of database design, but you could use bitfields. So your cleansing_verification is a BIT(4) type column, and each cleanser gets a bit they can set:
department = B'1000'
title = B'0100'
state = B'0010'
country = B'0001'
When running i.e. state, you would then:
UPDATE contacts
SET cleansing_verification = cleansing_verification | B'0010'
WHERE -- whatever conditions you want to apply
If you wanted to check which rows were updated by a given cleanser, you check if the bit is set, e.g. for state:
SELECT * FROM contacts WHERE cleansing_verification & B'0010' = B'0010'
Working example on dbfiddle
Actually proper way to do it would be to introduce a new table with a foreign key back to the contacts table and a column for a cleanser, like (quick'n'dirty example):
CREATE TABLE contacts_verification
(
contact_id int references contacts(id),
cleanser int
)
Then if you want to mark a record you just insert the contact id and some sort of cleanser identification (1, 2, 3, 4), or you can use a text field and meaningful names if you really want:
INSERT INTO contacts_verification (contact_id, cleanser) VALUES (21386, 1)
Then just use JOIN to get back the records marked by a cleanser:
SELECT c.*
FORM contacts c
JOIN contacts_verification dep_verify
ON dep_verify.contact_id = c.id
AND dep_verify.cleanser = 1
Related
There are clients(companies) and contacts in two tables. Both contacts and clients have their own fields. But they all have an id that is a primaryKey. In addition, there are "links" between clients and contacts - each client can be assigned a contact and vice versa. There is a third table for this, called 'assignment', which has only two fields - company id and contact id.
Suppose we have linked a contact with id 3 to a company with id 12076. Next, we have linked a contact with id 10, and the last contact with id 5. Сheck our result:
SELECT contactId FROM assignment WHERE companyId = 12076;
The result is correct -
After these steps, at some point I need to get the FIELDS of contacts associated with the company I need. There is a company 12076, I need to get all the contact fields associated with it. I made a request like this:
SELECT id, fullName FROM contacts WHERE contacts.rowid IN (SELECT contactId FROM assignment WHERE companyId = 12076);
This request displays the contacts I need and their fields. Exactly 3 contacts, but there is one problem - they are displayed in sorted order, sorted by id.
I need the contact fields to be displayed in the order in which they were added. How can i dow this? Maybe i need to use JOIN?
By default an SQLite table has a Rowid column. We can use this column in ORDER BY.
If we want the ContactId's in the order they were inserted into the table contacts we can join onto contacts and order by it's Rowid.
See [https://www.sqlitetutorial.net/sqlite-autoincrement/][1]
create table companies(id int);
create table contacts (id int);
create table assignment(companyId int,contactId int);
insert into companies values(12076);
insert into contacts values(10),(3),(5);
insert into assignment values (12076,3),(12076,10),(12076,5);
SELECT a.contactId
FROM assignment a
JOIN contacts c
on a.contactId = c.id
WHERE companyId = 12076
order by c.Rowid;
| contactId |
| --------: |
| 10 |
| 3 |
| 5 |
db<>fiddle here
I am working on an PostgreSQL based application and am very curious if there might be a clever solution to have language dependent column headers.
I sure know, that I can set an alias for a header with the "as" keyword, but that obviously has to be done for every select and over and over again.
So I have a table for converting the technical column name to a mnemonic one, to be shown to the user.
I can handle the mapping in the application, but would prefer a database solution. Is there any?
At least could I set the column header to table.column?
You could use a "view". You can think of a view as a psuedo-table, it can be created using a single or multiple tables created from a query. For instance, if I have a table that has the following shape
Table: Pets
Id | Name | OwnerId | AnimalType
1 | Frank| 1 | 1
2 | Jim | 1 | 2
3 | Bobo | 2 | 1
I could create a "view" that changes the Name field to look like PetName instead without changing the table
CREATE VIEW PetView AS
SELECT Id, Name as PetName, OwnerId, AnimalType
FROM Pets
Then I can use the view just like any other table
SELECT PetName
FROM PetView
WHERE AnimalType = 1
Further we could combine another table as well into the view. For instance if we add another table to our DB for Owners then we could create a view that automatically joins the two tables together before subjecting to other queries
Table: Owners
Id | Name
1 | Susan
2 | Ravi
CREATE VIEW PetsAndOwners AS
SELECT p.Id, p.Name as PetName, o.Name as OwnerName, p.AnimalType
FROM Pets p, Owners o
WHERE p.OwnerId = o.Id
Now we can use the new view again as in any other table (for querying, inserts and deletes are not supported in views).
SELECT * FROM PetsAndOwners
WHERE OwnerName = 'Susan'
Consider the following table named UserAttributes:
+----+--------+----------+-----------+
| Id | UserId | AttrName | AttrValue |
+----+--------+----------+-----------+
| 4 | 1 | FavFood | Apples |
| 3 | 2 | FavFood | Burgers |
| 2 | 1 | FavShape | Circle |
| 1 | 1 | FavFood | Chicken |
+----+--------+----------+-----------+
I would like to insert a new record in this table if the latest version of a particular attribute for a user has a value that does not match the latest.
What I mean by the latest is, for example, if I was to do:
SELECT TOP(1) * FROM [UserAttributes] WHERE [UserId] = 1 AND [AttrName] = 'FavFood' ORDER BY [Id] DESC
I will be able to see that user ID 1's current favorite food is "Apples".
Is there a query safe for concurrency that will only insert a new favorite food if it doesn't match the current favorite food for this user?
I tried using the MERGE query with a HOLDLOCK, but the problem is that WHEN MATCHED/WHEN NOT MATCHED, and that works if I never want to insert a new record after a user has previously set their favorite food (in this example) to the new value. However, it does not consider that a user might switch to a new favorite food, then subsequently change back to their old favorite food. I would like to maintain all the changes as a historical record.
In the data set above, I would like to insert a new record if the user ID 1's new favorite food is "Burgers", but I do not want to insert a record if their new favorite food is "Apples" (since that is their current favorite food). I would also like to make this operation safe for concurrency.
Thank you for your help!
EDIT: I should probably also mention that when I split this operation into two queries (ie: first select their current favorite food, then do an insert query only if there is a new food detected) it works under normal conditions. However, we are observing race conditions (and therefore duplicates) since (as you may have guessed) the data set above is simply an example and there are many threads operating on this table at the same time.
A bit ugly, but to do it in one command, you could insert the user's (new) favorite food but filter with an EXCEPT of their current values.
e.g., (assuming the user's new data is in #UserID, #FavFood
; WITH LatestFavFood AS
(SELECT TOP(1) UserID, AttrName, AttrValue
FROM [UserAttributes]
WHERE [UserId] = #UserID AND [AttrName] = 'FavFood'
ORDER BY [Id] DESC
)
INSERT INTO UserAttributes (UserID, AttrName, AttrValue)
SELECT #UserID, 'FavFood', #FavFood
EXCEPT
SELECT UserID, AttrName, AttrValue
FROM LatestFavFood
Here's a DB_Fiddle with three runs.
EDIT: I have changed the above to assume varchar types for AttrName rather than nvarchar. The fiddle has a mixture. Would be good to ensure you get them correct (especially food as it may have special characters).
The architecture of my DB involves records in a Tags table. Each record in the Tags table has a string which is a Name and a foreign kery to the PrimaryID's of records in another Worker table.
Records in the Worker table have tags. Every time we create a Tag for a worker, we add a new row in the Tags table with the inputted Name and foreign key to the worker's PrimaryID. Therefore, we can have multiple Tags with different names per same worker.
Worker Table
ID | Worker Name | Other Information
__________________________________________________________________
1 | Worker1 | ..........................
2 | Worker2 | ..........................
3 | Worker3 | ..........................
4 | Worker4 | ..........................
Tags Table
ID |Foreign Key(WorkerID) | Name
__________________________________________________________________
1 | 1 | foo
2 | 1 | bar
3 | 2 | foo
5 | 3 | foo
6 | 3 | bar
7 | 3 | baz
8 | 1 | qux
My goal is to filter WorkerID's based on an inputted table of strings. I want to get the set of WorkerID's that have the same tags as the inputted ones. For example, if the inputted strings are foo and bar, I would like to return WorkerID's 1 and 3. Any idea how to do this? I was thinking something to do with GROUP BY or JOINING tables. I am new to SQL and can't seem to figure it out.
This is a variant of relational division. Here's one attempt:
select workerid
from tags
where name in ('foo', 'bar')
group by workerid
having count(distinct name) = 2
You can use the following:
select WorkerID
from tags where name in ('foo', 'bar')
group by WorkerID
having count(*) = 2
and this will retrieve your desired result/
Regards.
This article is an excellent resource on the subject.
While the answer from #Lennart works fine in Query Analyzer, you're not going to be able to duplicate that in a stored procedure or from a consuming application without opening yourself up to SQL injection attacks. To extend the solution, you'll want to look into passing your list of tags as a table-valued parameter since SQL doesn't support arrays.
Essentially, you create a custom type in the database that mimics a table with only one column:
CREATE TYPE list_of_tags AS TABLE (t varchar(50) NOT NULL PRIMARY KEY)
Then you populate an instance of that type in memory:
DECLARE #mylist list_of_tags
INSERT #mylist (t) VALUES('foo'),('bar')
Then you can select against that as a join using the GROUP BY/HAVING described in the previous answers:
select workerid
from tags inner join #mylist on tag = t
group by workerid
having count(distinct name) = 2
*Note: I'm not at a computer where I can test the query. If someone sees a flaw in my query, please let me know and I'll happily correct it and thank them.
Let's say I have two tables: Customer and City. There are many Customers that live in the same City. The cities have an uid that is primary key. The customers have a foreign key reference to their respective city via Customer.city_uid.
I have to swap two City.uids with one another for external reasons. But the customers should stay attached to their cities. Therefore it is necessary to swap the Customer.city_uids as well. So I thought I first swap the City.uids and then change the Customer.city_uids accordingliy via an UPDATE-statement. Unfortunately, I can not do that since these uids are referenced from the Customer-table and PostgreSQL prevents me from doing that.
Is there an easy way of swapping the two City.uids with one another as well as the Customer.city_uids?
One solution could be:
BEGIN;
1. Drop foreign key
2. Make update
3. Create foreign key
COMMIT;
Or:
BEGIN;
1. Insert "new" correct information
2. Remove outdated information
COMMIT;
My instinct is to recommend not trying to change the city table's id field. But there is lot of information missing here. So it really is a feeling rather than a definitive point of view.
Instead, I would swap the values in the other fields of the city table. For example, change the name of city1 to city2's name, and vice-versa.
For example:
OLD TABLE NEW TABLE
id | name | population id | name | population
------------------------- -------------------------
1 | ABerg | 123456 1 | BBerg | 654321
2 | BBerg | 654321 2 | ABerg | 123456
3 | CBerg | 333333 3 | CBerg | 333333
(The ID was not touched, but the other values were swapped. Functionally the same as swapping the IDs, but with 'softer touch' queries that don't need to make any changes to table constraints, etc.)
Then, in your associated tables, you can do...
UPDATE
Customer
SET
city_uid = CASE WHEN city_uid = 1 THEN 2 ELSE 1 END
WHERE
city_uid IN (1,2)
But then, do you have other tables that reference city_uid? And if so, is it feasible for you to repeat that update on all those tables?
You could create two temporary cities.
You would have:
City 1
City 2
City Temp 1
City Temp 2
Then, you could do the follow:
Update all Customer UIDs from City 1 to City Temp 1.
Update all Customer UIDs from City 2 to City Temp 2.
Swap City 1 and 2 UIDs
Move all Customers back from City Temp 1 to City 1.
Move all Customers back from City Temp 2 to City 2.
Delete the temporally cities.
You can also add an ON UPDATE CASCADE clause to the parent table's CREATE TABLE statement, as described here:
How to do a cascading update?