Say I got this SQL schema.
Table Job:
id,title, type, is_enabled
Table JobFileCopy:
job_id,from_path,to_path
Table JobFileDelete:
job_id, file_path
Table JobStartProcess:
job_id, file_path, arguments, working_directory
There are many other tables with varying number of columns and they all got foreign key job_id which is linked to id in table Job.
My questions:
Is this the right approach? I don't have requirement to delete anything at anytime. I will require to select and insert mostly.
Secondly, what is the best approach to get the list of jobs with relevant details from all the different tables in a single database hit? e.g I would like to select top 20 jobs with details, their details can be in any table (depends on column type in table Job) which I don't know until runtime.
select (case when type = 'type1' then (select field from table1) else (select field from table2) end) as a from table;
Could it be a solution for you?
Related
I have a table like this
CREATE TABLE userinteractions
(
userid bigint,
dobyr int,
-- lots more fields that are not relevant to the question
);
My problem is that some of the data is polluted with multiple dobyr values for the same user.
The table is used as the basis for further processing by creating a new table. These cases need to be removed from the pipeline.
I want to be able to create a clean table that contains unique userid and dobyr limited to the cases where there is only one value of dobyr for the userid in userinteractions.
For example I start with data like this:
userid,dobyr
1,1995
1,1995
2,1999
3,1990 # dobyr values not equal
3,1999 # dobyr values not equal
4,1989
4,1989
And I want to select from this to get a table like this:
userid,dobyr
1,1995
2,1999
4,1989
Is there an elegant, efficient way to get this in a single sql query?
I am using postgres.
EDIT: I do not have permissions to modify the userinteractions table, so I need a SELECT solution, not a DELETE solution.
Clarified requirements: your aim is to generate a new, cleaned-up version of an existing table, and the clean-up means:
If there are many rows with the same userid value but also the same dobyr value, one of them is kept (doesn't matter which one), rest gets discarded.
All rows for a given userid are discarded if it occurs with different dobyr values.
create table userinteractions_clean as
select distinct on (userid,dobyr) *
from userinteractions
where userid in (
select userid
from userinteractions
group by userid
having count(distinct dobyr)=1 )
order by userid,dobyr;
This could also be done with an not in, not exists or exists conditions. Also, select which combination to keep by adding columns at the end of order by.
Updated demo with tests and more rows.
If you don't need the other columns in the table, only something you'll later use as a filter/whitelist, plain userid's from records with (userid,dobyr) pairs matching your criteria are enough, as they already uniquely identify those records:
create table userinteractions_whitelist as
select userid
from userinteractions
group by userid
having count(distinct dobyr)=1
Just use a HAVING clause to assert that all rows in a group must have the same dobyr.
SELECT
userid,
MAX(dobyr) AS dobyr
FROM
userinteractions
GROUP BY
userid
HAVING
COUNT(DISTINCT dobyr) = 1
I have 2 tables. Table 1 has data from the bank account. Table 2 aggregates data from multiple other tables; to keep things simple, we will just have 2 tables. I need to append the data from table 1 into table 2.
I have a field in table2, "SrceFk". The concept is that when a record from Table1 appends, it will fill the table2.SrceFk with the table1 primary key and the table name. So record 302 will look like "BANK/302" after it appends. This way, when I run the append query, I can avoid duplicates.
The query is not working. I deleted the record from table2, but when I run the query, it just says "0 records appended". Even though the foreign key is not present.
I am new to SQL, Access, and programming in general. I understand basic concepts. I have googled this issue and looked on stackOverflow, but no luck.
This is my full statement:
INSERT INTO Main ( SrceFK, InvoDate, Descrip, AMT, Ac1, Ac2 )
SELECT Bank.ID &"/"& "BANK", Bank.TransDate, Bank.Descrip, Bank.TtlAmt, Bank.Ac1, Bank.Ac2
FROM Bank
WHERE NOT EXISTS
(
SELECT * FROM Main
WHERE Main.SrceFK = Bank.ID &"/"& "BANK"
);
I expect the query to add records that aren't present in the table, as needed.
Say I have two customer tables which have pretty much the same columns. One of them is a temporal one which periodically updates the other one. That is, updates and additions to the records are done to the temporal table only. Say they're names are CUSTOMER, and CUSTOMER_TEMP.
The tables got information like ID, NAME, LAST_NAME, and ADDRESS.
This temporal table has three extra fields, TEMP_ID, RECORD_TYPE, and DATE. The record type is used to record whether there was an addition or an update. So the thing is I need to select the latest record from both tables. That involves several cases
Main table has record, but temporal doesn't -> Select main table record.
Main table has no record, but temporal does -> Select latest temporal table record.
Main table has record and temporal has an add record -> Select temporal table record.
Main table has record and temporal table has update record -> Select temporal table record.
Main table has record and temporal table has add and update record. -> Select temporal table update record.
Main table has record and temporal table has various update records. -> Select latest temporal table update record.
Main table has record and temporal table has add record and various update records. -> Select latest temporal table update record.
Now, I don't know whether this is a good flow or not. I was just told to make the query, so I don't have access to the DB, I believe I could make suggestions though. The thing is My SLQ knowledge is not enough to build this query. I know there's an INNER_JOIN involved, as well as a filter by date, and probably and EXIST, to check whether the record exist or not in the CUSTOMER_TEMP table. But I don't quite know how to build it. I'm working on .Net And SQLServer. Any help on it is quite appreciated.
select m.*, 0 as [rn]
from main m
where not exists (select 1 from temp where temp.id = m.id)
union
select tt.*
from ( select temp.*
, row_number() over (partition by id order by RECORD_TYPE desc, date desc) as rn
from temp
-- join main
-- on temp.ID = main.ID
) tt
where tt.rn = 1
if update does not sort last then need to do a trick like in the answer from Tom H
;WITH CTE_Latest_Temporal AS
(
SELECT
id,
name,
..., -- Put the rest of your columns here
ROW_NUMBER OVER (PARTITION BY id
ORDER BY
CASE record_type
WHEN 'Update' THEN 0
ELSE 1
END, date DESC) AS row_num
FROM
Customer_Temp
)
SELECT
M.id,
CASE WHEN T.id IS NOT NULL THEN T.name ELSE M.name END AS name,
... -- Similar CASE statements for the rest of your columns
FROM
Customer M
LEFT OUTER JOIN CTE_Latest_Temporal T ON
T.id = M.id AND
T.row_num = 1
The CASE statements can be replaced by a simple COALESCE(T.column, M.column) for any columns that cannot be NULL. I had to use the CASE to cover situations where the row might exist in the temp table but the column might be NULL in the temp table, but have a value in the main table.
I have a table with a certain number of columns and a primary key column (suppose OriginalKey). I perform a GROUP BY on a certain sub-set of those columns and store them in a temporary table with primary key (suppose GroupKey). At a later stage, I may need to get more details about one or more of those groupings (which can be found in the temporary table) i.e. I need to know which were the rows from the original table that formed that group. Simply put, I need to know the mappings between GroupKey and OriginalKey. What's the best way to do this? Thanks in advance.
Example:
Table Student(
StudentID INT PRIMARY KEY,
Level INT, --Grade/Class/Level depending on which country you are from)
HomeTown TEXT,
Gender CHAR)
INSERT INTO TempTable SELECT HomeTown, Gender, COUNT(*) AS NumStudents FROM Student GROUP BY HomeTown, Gender
On a later date, I would like to find out details about all towns that have more than 50 male students and know details of every one of them.
How about joining the 2 tables using the GroupKey, which, you say, are the same?
Or how about doing:
select * from OriginalTable where
GroupKey in (select GroupKey from my_temp_table)
You'd need to store the fields you grouped on in your temporary table, so you can join back to the original table. e.g. if you grouped on fieldA, fieldB, and fieldC, you'd need something like:
select original.id
from original
inner join temptable on
temptable.fieldA = original.fieldA and
temptable.fieldB = original.fieldB and
temptable.fieldC = original.fieldC
I'm trying to normalize a mysql database....
I currently have a table that contains 11 columns for "categories". The first column is a user_id and the other 10 are category_id_1 - category_id_10. Some rows may only contain a category_id up to category_id_1 and the rest might be NULL.
I then have a table that has 2 columns, user_id and category_id...
What is the best way to transfer all of the data into separate rows in table 2 without adding a row for columns that are NULL in table 1?
thanks!
You can create a single query to do all the work, it just takes a bit of copy and pasting, and adjusting the column name:
INSERT INTO table2
SELECT * FROM (
SELECT user_id, category_id_1 AS category_id FROM table1
UNION ALL
SELECT user_id, category_id_2 FROM table1
UNION ALL
SELECT user_id, category_id_3 FROM table1
) AS T
WHERE category_id IS NOT NULL;
Since you only have to do this 10 times, and you can throw the code away when you are finished, I would think that this is the easiest way.
One table for users:
users(id, name, username, etc)
One for categories:
categories(id, category_name)
One to link the two, including any extra information you might want on that join.
categories_users(user_id, category_id)
-- or with extra information --
categories_users(user_id, category_id, date_created, notes)
To transfer the data across to the link table would be a case of writing a series of SQL INSERT statements. There's probably some awesome way to do it in one go, but since there's only 11 categories, just copy-and-paste IMO:
INSERT INTO categories_users
SELECT user_id, 1
FROM old_categories
WHERE category_1 IS NOT NULL