I am dealing with more than 25 tables which having association and I need to return a simple array/cursor from my stored procedure.
To make simple my question I am providing below example:-
For mentioned below scenario I want to add subjects against each student means in existing emp_curr I want to add result of sub_cur.
cursor emp_curr is
select st_id,st_name,st_surname from student;
BEGIN
FOR n IN emp_curr LOOP
DECLARE
cursor sub_cur is
select sub_id,subject from student_subjects where st_id_fk=n.st_id;
BEGIN
FOR c IN sub_cur LOOP
-- Here I want to store sub_cur values in existing emp_curr
end loop;
END;
end loop;
END;
Final Output
|-----------|--------------|----------|---------------|-
|Student ID | Student Name |Student ID|Student subject|
|-----------|--------------|----------|---------------|-
| 1 | prashant | 2 | Maths |
| 1 | prashant | 4 | English |
| 1 | prashant | 3 | Science |
|-----------|--------------|----------|---------------|-
| 2 | shailndra | 1 | Hindi |
| 2 | shailndra | 5 | Geo |
| 2 | shailndra | 7 | Chemical |
|-----------|--------------|----------|---------------|-
It will be great if you can help me as I have already spent 4 hours and its gone in vain.
Prashant Thakre, how are you? Perhaps I misunderstood your question, so I will explain myself and hopefully, help you. The first thing I realized from your scenario is it's odd. You cannot change an Oracle cursor structure once you have declared it. More than that, I don't see the need to implement such a procedure. You use two columns from the table STUDENT, am I right? Then, you need two more columns added to your data set, those two coming from the table STUDENT_SUBJECTS. And it seems to exist some referential integrity between those tables, because you have an equijoin condition in the second cursor's query ( ...where st_id_fk=n.st_id)
So, I wonder, why don't you open the first cursor setting the following query, so you don't need to add those columns "by hand"?
select s.st_id,s.st_name,s.st_surname,sb.sub_id,sb.subject
from student s,student_subjects sb
where s.st_id=sb.st_id_fk
Using that query, you have want you are looking for, what you are needing.
Again, maybe I misunderstood your issue, but I really want to help you. So, give more ight"on the subject if that query is not what you need.
Best regards.
Jorge.
Related
Aware there is an almost identical question here, but that covers the SQL query required, rather than the mechanism of event triggering.
Lets say I have two tables. One table contains performance data for each staff member each week. The other table is a table that holds the staff members information. What I want is to update a value in the table to a Y or N based on whether that staff member left at the week date.
staffTable
+----------+----------------+------------+
| staff_id | staff_name | leave_date |
+----------+----------------+------------+
| 1 | Joseph Blogges | 2020-01-24 |
| 2 | Joe Bloggs | 9999-12-31 |
| 3 | Joey Blogz | 9999-12-31 |
+----------+----------------+------------+
targetTable
+------------+----------+--------+-----------+
| week_start | staff_id | target | left_flag |
+------------+----------+--------+-----------+
| 2020-01-13 | 1 | 10 | N |
| 2020-01-20 | 1 | 10 | N |
| 2020-01-27 | 1 | 8 | Y |
+------------+----------+--------+-----------+
What I am trying to do is have the left_flag automatically change from 'N' to 'Y' when the week_start value is greater than leave_date of the staff member (in the other table).
I have tried successfully putting this into a view, which works, but the problem is that existing applications, views and queries will need to all reference a new view instead of a table and I want to be able to query the data table as my front-end has issues interacting in live with a view instead of a table.
I have also successfully used a UDF to return the leave_date and then create computed column that will check if this UDF variable is greater than the start_date column and this worked fine until I realised that the UDF is the most resource consuming query on the entire server and is completely disproportionate.
Is there a way that I can trigger an update to the staffTable when a criteria is met in another table, or is there a totally better and different way of doing this? If it can't be done easily, I'll try to switch to a view and work around it in the front-end.
I'm going to describe the process rather than writing the code.
What you are describing can be accomplished using triggers on staffTable. When a new row is inserted or updated the trigger would change any rows in targetTable. This would be an after insert/update trigger.
The heart of the trigger would be:
update tt
set left_flag = 'Y'
from targettable tt join
inserted i
on tt.staff_id = i.staff_id
where i.leave_date < tt.week_start and
tt.left_flag <> 'Y';
I am facing an issue where a data supplier is generating a dump of his multi-tenant databases in a single table. Recreating the original tables is not impossible, the problem is I am receiving millions of rows every day. Recreating everything, every day, is out of question.
Until now, I was using SSIS to do so, with a lookup-intensive approach. In the past year, my virtual machine went from having 2 GB of ram to 128, and still growing.
Let me explain the disgrace:
Imagine a database where users have posts, and posts have comments. In my real scenario, I am talking about 7 distinct tables. Analyzing a few rows, I have the following:
+-----+------+------+--------+------+-----------+------+----------------+
| Id* | T_Id | U_Id | U_Name | P_Id | P_Content | C_Id | C_Content |
+-----+------+------+--------+------+-----------+------+----------------+
| 1 | 1 | 1 | john | 1 | hello | 1 | hello answer 1 |
| 2 | 1 | 2 | maria | 2 | cake | 2 | cake answer 1 |
| 3 | 2 | 1 | pablo | 1 | hello | 1 | hello answer 3 |
| 4 | 2 | 1 | pablo | 2 | hello | 2 | hello answer 2 |
| 5 | 1 | 1 | john | 3 | nosql | 3 | nosql answer 1 |
+-----+------+------+--------+------+-----------+------+----------------+
the Id is from my table
T_Id is the "tenant" Id, which identifies multiple databases
I have imagined the following possible solution:
I make a query that selects non-existent Ids for each table, such as:
SELECT DISTINCT n.t_id,
n.c_id,
n.c_content
FROM mytable n
WHERE n.id > 4
AND NOT EXISTS (SELECT 1
FROM mytable o
WHERE o.id <= 4
AND n.t_id = o.t_id
AND n.c_id = o.c_id)
This way, I am able to select only the new occurrences whenever a new Id of a table is found. Although it works, it may perform badly when working with 100s of millions of rows.
Could anyone share a suggestion? I am quite lost.
Thanks in advance.
EDIT > my question is vague
My final intent is to rebuild the tables from the dump, incrementally, avoiding lookups outside the database. Every now and then I am gonna run a script that will select new tenants, users, posts and comments and add them to their corresponding tables.
My previous solution worked as follows:
Cache the whole database
For each new row, search for the columns inside the cache
If it doesn't exist, then insert it
I know it sounds dumb, but it made sense as a new developer working with ETLs
First, if you have a full flat DB dump, I'll suggest you to work on your file before even importing it in your DB (low level file processing is pretty cheap and nearly instantaneous).
From Removing lines in one file that are present in another file using python you can remove all the already parsed line since your last run.
with open('new.csv','r') as source:
lines_src = source.readlines()
with open('old.csv','r') as f:
lines_f = f.readlines()
destination = open('diff_add.csv',"w")
for data in lines_src:
if data not in lines_f:
destination.write(data)
destination.close()
This take less than five second to work on a 900Mo => 1.2Go dump. With this you'll only work with line that really make change in one of your new table.
Now you can import this flat DB to a working table.
As you'll have to search the needle in each line, some index on the ids may by a good idea (go to composite index that use your Tenant_id first).
For the last part, I don't know exactly how your data look, can you have some update to do ?
The Operators - EXCEPT and INTERSECT can help you too with this kind of problem.
I'm a bit stumped on a query I need to write for work. I have the following two tables:
|===============Patterns==============|
|type | bucket_id | description |
|-----------------------|-------------|
|pattern a | 1 | Email |
|pattern b | 2 | Phone |
|==========Results============|
|id | buc_1 | buc_2 |
|-----------------------------|
|123 | pass | |
|124 | pass |fail |
In the results table, I can see that entity 124 failed a validation check in buc_2. Looking at the patterns table, I can see bucket 2 belongs to pattern b (bucket_id corresponds to the column name in the results table), so entity 124 failed phone validation. But how do I write a query that joins these two tables on the value of one of the columns? Limitations to how this query is going to be called will most likely prevent me from using any cursors.
Some crude solutions:
SELECT "id", "description" FROM
Results JOIN Patterns
ON "buc_1" = 'fail' AND "bucket_id" = 1
union all
SELECT "id", "description" FROM
Results JOIN Patterns
ON "buc_2" = 'fail' AND "bucket_id" = 2
Or, with a very probably better execution plan:
SELECT "id", "description" FROM
Results JOIN Patterns
ON "buc_1" = 'fail' AND "bucket_id" = 1
OR "buc_2" = 'fail' AND "bucket_id" = 2;
This will report all failure descriptions for each id having a fail case in bucket 1 or 2.
See http://sqlfiddle.com/#!4/a3eae/8 for a live example
That being said, the right solution would be probably to change your schema to something more manageable. Say by using an association table to store each failed test -- as you have in fact here a many to many relationship.
An other approach if you are using Oracle ≥ 11g, would be to use the UNPIVOT operation. This will translate columns to rows at query execution:
select * from Results
unpivot ("result" for "bucket_id" in ("buc_1" as 1, "buc_2" as 2))
join Patterns
using("bucket_id")
where "result" = 'fail';
Unfortunately, you still have to hard-code the various column names.
See http://sqlfiddle.com/#!4/a3eae/17
It looks to me that what you really want to know is the description(in your example Phone) of a Pattern entry given the condition that the bucket failed. Regardless of the specific example you have you want a solution that fulfills that condition, not just your particular example.
I agree with the comment above. Your bucket entries should be tuples(rows) and not arguments, and also you should share the ids on each table so you can actually join them. For example, Consider adding a bucket column and index their number then just add ONE result column to store the state. Like this:
|===============Patterns==============|
|type | bucket_id | description |
|-----------------------|-------------|
|pattern a | 1 | Email |
|pattern b | 2 | Phone |
|==========Results====================|
|entity_id | bucket_id |status |
|-------------------------------------|
|123 | 1 |pass |
|124 | 1 |pass |
|123 | 2 | |
|124 | 2 |fail |
1.-Use an Inner Join: http://www.w3schools.com/sql/sql_join_inner.asp and the WHERE clause to filter only those buckets that failed:
2.-Would this example help?
SELECT Patterns.type, Patterns.description, Results.entity_id,Results.status
INNER JOIN Results
ON
Patterns.bucket_id=Results.bucket_id
WHERE
Results.status=fail
Lastly, I would also add a primary_key column to each table to make sure indexing is faster for each unique combination.
Thanks!
I'm facing a database that keeps the ORDERING in columns of the table.
It's like:
Id Name Description Category OrderByName OrderByDescription OrderByCategory
1 Aaaa bbbb cccc 1 2 3
2 BBbbb Aaaaa bbbb 2 1 2
3 cccc cccc aaaaa 3 3 1
So, when the user want's to order by name, the SQL goes with an ORDER BY OrderByName.
I think this doesn't make any sense, since that's why Index are for and i tried to find any explanation for that but haven't found. Is this faster than using indexes? Is there any scenario where this is really useful?
It can make sense for many reasons but mainly when you don't want to follow the "natural order" given by the ORDER BY clause.
This is a scenario where this can be useful :
SQL Fiddle
MS SQL Server 2008 Schema Setup:
CREATE TABLE Table1
([Id] int, [Name] varchar(15), [OrderByName] int)
;
INSERT INTO Table1
([Id], [Name], [OrderByName])
VALUES
(1, 'Del Torro', 2 ),
(2, 'Delson', 1),
(3, 'Delugi', 3)
;
Query 1:
SELECT *
FROM Table1
ORDER BY Name
Results:
| ID | NAME | ORDERBYNAME |
|----|-----------|-------------|
| 1 | Del Torro | 2 |
| 2 | Delson | 1 |
| 3 | Delugi | 3 |
Query 2:
SELECT *
FROM Table1
ORDER BY OrderByName
Results:
| ID | NAME | ORDERBYNAME |
|----|-----------|-------------|
| 2 | Delson | 1 |
| 1 | Del Torro | 2 |
| 3 | Delugi | 3 |
I think it makes little sense for two reasons:
Who is going to maintain this set of values in the table? You need to update them every time any row is added, updated, or deleted. You can do this with triggers, or horribly buggy and unreliable constraints using user-defined functions. But why? The information that seems to be in those columns is already there. It's redundant because you can get that order by ordering by the actual column.
You still have to use massive conditionals or dynamic SQL to tell the application how to order the results, since you can't say ORDER BY #column_name.
Now, I'm basing my assumptions on the fact that the ordering columns still reflect the alphabetical order in the relevant columns. It could be useful if there is some customization possible, e.g. if you wanted all Smiths listed first, and then all Morts, and then everyone else. But I don't see any evidence of this in the question or the data.
This could be useful if the ordering was customizable - that is, if users did not want to see the list in alphabetical order, but rather in some custom order.
An index on the int columns would be smaller than an index on the column that holds the actual text, but I don't see that there is any real benefit to this in most cases.
I have an sqlite database table similar to the one given below
Name | Surname | AddrType | Age | Phone
John | Kruger | Home | 23 | 12345
Sarah | Kats | Home | 33 | 12345
Bill | Kruger | Work | 15 | 12345
Lars | Kats | Home | 54 | 12345
Javier | Roux | Work | 45 | 12345
Ryne | Hutt | Home | 36 | 12345
I would like to select Name values matching same "Surname" value for each of the rows in the table.
For example, for the first line the query would be "select Name from myTable where Surname='Kruger'" whereas for the second line the query would be "select Name from myTable where Surname='Kats' and so an....
Is it possible to traverse through the whole table and select all values like that?
PS : I will use these method in a C++ application, the alternative method is to use sqlite3_exec() and process each row one by one. I just want to know if there is any other possible way for the same approach.
I'd do:
sqlite> SELECT group_concat(Name, '|') Names FROM People GROUP BY Surname;
Names
----------
Ryne
Sarah|Lars
John|Bill
Javier
Then split each value of "Names" in C++ using the "|" separator (or any other you choose in group_concat function.
Basically you just want to exclude any records that don't have a buddy.
Something simple like joining the table against itself should work:
SELECT a.Name
FROM tab AS a
JOIN tab AS b
ON a.Surname = b.Surname;
Just returning the full sorted table and doing the duplicate check yourself may be faster if incidence is high (and will always be high for all sets of data). That would be a pretty strong assumption though.
SELECT Name
FROM tab
SORT BY Surname;