I have 2 tables A and B. I need to update a column in table A for all userid's based on the count of records that userid has in another table based on defined rules. If count of records in another table is 3 and is required for that userID, then mark IsCorrect as 1 else 0, if count is 2 and required is 5 then IsCorrect as 0 For e.g. Below is what I am trying to achieve
Table A
UserID | Required | IsCorrect
----------------------------------
1 | SO;GO;PE | 1
2 | SO;GO;PE;PR | 0
3 | SO;GO;PE | 1
Table B
UserID | PPName
-----------------------
1 | SO
1 | GO
1 | PE
2 | SO
2 | GO
3 | SO
3 | GO
3 | PE
I tried using Update in table joining another table, but cannot up with one. Also, do not want to use cursors, because of its overhead. I know I will have to create a stored Procedure for it for the rules, but how to pass the userID's to it without cursor is what am i am looking for.
Thanks for the help. Apologies for not formatting the table correctly :)
update A
set IsCorrect = case
when Required <= (select count(*) from B where b.UserID = A.UserID)
then 'Y' -- or 0, or whatever sense is appropriate
else 'N'
end
THIS ANSWERS THE ORIGINAL QUESTION.
Hmmm, you can use a correlated subquery and some case logic:
update a
set iscorrect = (case when required <=
(select count(*) from b where b.userid = a.userid)
then 1 else 0
end);
Related
I want to have the column "CurrentCapacity" to be the SUM of all references specific column.
Lets say there are three rows in SecTable which all have FirstTableID = 1. Size values are 1, 1 and 3.
The row in FirstTable which have ID = 1 should now have a value of 5 in the CurrentCapacity column.
How can I make this and how to do automatically on insert, update and delete?
Thanks!
FirstTable
+----+-------------+-------------------------+
| ID | MaxCapacity | CurrentCapacity |
+----+-------------+-------------------------+
| 1 | 5 | 0 (desired result = 5) |
+----+-------------+-------------------------+
| 2 | 5 | 0 |
+----+-------------+-------------------------+
| 3 | 5 | 0 |
+----+-------------+-------------------------+
SecTable
+----+-------------------+------+
| ID | FirstTableID (FK) | Size |
+----+-------------------+------+
| 1 | 1 | 2 |
+----+-------------------+------+
| 2 | 1 | 3 |
+----+-------------------+------+
In general, a view is a better solution than trying to keep a calculated column up-to-date. For your example, you could use this:
CREATE VIEW capacity AS
SELECT f.ID, f.MaxCapacity, COALESCE(SUM(s.Size), 0) AS CurrentCapacity
FROM FirstTable f
LEFT JOIN SecTable s ON s.FirstTableID = f.ID
GROUP BY f.ID, f.MaxCapacity
Then you can simply
SELECT *
FROM capacity
to get the results you desire. For your sample data:
ID MaxCapacity CurrentCapacity
1 5 5
2 5 0
3 5 0
Demo on SQLFiddle
Got this question to work with this trigger:
CREATE TRIGGER UpdateCurrentCapacity
ON SecTable
AFTER INSERT, UPDATE, DELETE
AS
BEGIN
SET NOCOUNT ON
DECLARE #Iteration INT
SET #Iteration = 1
WHILE #Iteration <= 100
BEGIN
UPDATE FirstTable SET FirstTable.CurrentCapacity = (SELECT COALESCE(SUM(SecTable.Size),0) FROM SecTable WHERE FirstTableID = #Iteration) WHERE ID = #Iteration;
SET #Iteration = #Iteration + 1
END
END
GO
Personally, I would not use a trigger either or store CurrentCapacity as a value since it breaks Normalization rules for database design. You have a relation and can already get the results by creating a view or setting CurrentCapacity to a calculated column.
Your view can look like this:
SELECT Id, MaxCapacity, ISNULL(O.SumSize,0) AS CurrentCapacity
FROM dbo.FirstTable FT
OUTER APPLY
(
SELECT ST.FirstTableId, SUM(ST.Size) as SumSize FROM SecTable ST
WHERE ST.FirstTableId = FT.Id
GROUP BY ST.FirstTableId
) O
Sure, you could fire a proc every time a row is updated/inserted or deleted in the second table and recalculate the column, but you might as well calculate it on the fly. If it's not required to have the column accurate, you can have a job update the values every X hours. You could combine this with your view to have both a "live" and "cached" version of the capacity data.
SQL Server 2016
I have a number of tables
Table A Table B Table C Table D
User | DataA User | DataB User | DataC User | DataD
=========== =========== =================== =============
1 | 10 1 | 'hello' 4 | '2020-01-01' 1 | 0.34
2 | 20 2 | 'world'
3 | 30
So some users have data for A,B,C and/or D.
Table UserEnabled
User | A | B | C | D
=============================
1 | 1 | 1 | 0 | 0
2 | 1 | 1 | 0 | 0
3 | 1 | 0 | 0 | 0
4 | 0 | 0 | 1 | 0
Table UserEnabled indicates whether we are interested in any of the data in the corresponding tables A,B,C and/or D.
Now I want to join those tables on User but I do only want the columns where the UserEnabled table has at least one user with a 1 (ie at least one user enabled). Ideally I only want to join the tables that are enabled and not filter the columns from the disabled tables afterwards.
So as a result for all users I would get
User | DataA | DataB | DataC
===============================
1 | 10 | 'hello' | NULL
2 | 20 | 'world' | NULL
3 | 30 | NULL | NULL
4 | NULL | NULL | '2020-01-01'
No user has D enabled so it does not show up in a query
I was going to come up with a dynamic SQL that's built every time I execute the query depending on the state of UserEnabled but I'm afraid this is going to perform poorly on a huge data set as the execution plan will need to be created every time. I want to dynamically display only the enabled data, not columns with all NULL.
Is there another way?
Usage will be a data sheet that may be generated up to a number of times per minute.
You have no choice but to approach this through dynamic SQL. A select query has a fixed set of columns defined when the query is created. No such thing as "variable" columns.
What can you do? One method is to "play a trick". Store the columns as JSON (or XML) and delete the empty columns.
Another method is to create a view that has the specific logic you need. I think you can maintain this view by altering it in a trigger, based on when data in the enabled table changes. That said, altering the view requires dynamic SQL so the code will not be pretty.
Just because I thought this could be fun.
Example
Declare #Col varchar(max) = ''
Declare #Src varchar(max) = ''
Select #Col = #Col+','+Item+'.[Data'+Item+']'
,#Src = #Src+'Left Join [Table'+Item+'] '+Item+' on U.[User]=['+Item+'].[User] and U.['+Item+']=1'+char(13)
From (
Select Item
From ( Select A=max(A)
,B=max(B)
,C=max(C)
,D=max(D)
From UserEnabled
Where 1=1 --<< Use any Key Inital Filter Condition Here
) A
Unpivot ( value for item in (A,B,C,D)) B
Where Value=1
) A
Declare #SQL varchar(max) = '
Select U.[User]'+#Col+'
From #UserEnabled U
'+#Src
--Print #SQL
Exec(#SQL)
Returns
User DataA DataB DataC
1 10 Hello NULL
2 20 World NULL
3 30 NULL NULL
4 NULL NULL 2020-01-01
The Generated SQL
Select A.[User],A.[DataA],B.[DataB],C.[DataC]
From UserEnabled U
Left Join TableA A on U.[User]=[A].[User] and U.[A]=1
Left Join TableB B on U.[User]=[B].[User] and U.[B]=1
Left Join TableC C on U.[User]=[C].[User] and U.[C]=1
If all the relations are 1:1, you can make one query with
...
FROM u
LEFT JOIN a ON u.id = a.u_id
LEFT JOIN b ON u.id = b.u_id
LEFT JOIN c ON u.id = c.u_id
LEFT JOIN d ON u.id = d.u_id
...
and use display logic on the client to omit the irrelevant columns.
If more than one relation is 1:N, then you'd likely have to do multiple queries anyway to prevent N1xN2 results.
I have 2 tables A and B. I need to update a column in table A for all userid's based on the count of records that userid has in another table based on defined rules. If count of records in another table is 3 and is required for that userID, then mark IsCorrect as 1 else 0, if count is 2 and required is 5 then IsCorrect as 0 For e.g. Below is what I am trying to achieve
Table A
UserID | Required | IsCorrect
----------------------------------
1 | SO;GO;PE | 1
2 | SO;GO;PE;PR | 0
3 | SO;GO;PE | 1
Table B
UserID | PPName
-----------------------
1 | SO
1 | GO
1 | PE
2 | SO
2 | GO
3 | SO
3 | GO
3 | PE
I tried using Update in table joining another table, but cannot up with one. Also, do not want to use cursors, because of its overhead. I know I will have to create a stored Procedure for it for the rules, but how to pass the userID's to it without cursor is what am i am looking for.
This is an update for my earlier question. Thanks for the help.
Here's a solution for PostgreSQL:
update TableA
set IsCorrect =
case when
string_to_array(Required, ';') <#
(select array_agg(PPName)
from TableB
where TableA.UserID = TableB.UserID)
then 1
else 0
end;
You can also see it live on SQL Fiddle.
use sub-query and aggregate function and then case when for conditional update
update TableA A
set A.IsCorrect= case when T.cnt>=3 then 1 else 0 end
inner join
(
select B.UserID ,count(*) as cnt from TableB as B
group by UserID
) as T
on A.userid=T.UserID
I have a Family table:
SELECT * FROM Family;
id | Surname | Oldest | Oldest_Age
---+----------+--------+-------
1 | Byre | NULL | NULL
2 | Summers | NULL | NULL
3 | White | NULL | NULL
4 | Anders | NULL | NULL
The Family.Oldest column is not yet populated. There is another table of Children:
SELECT * FROM Children;
id | Name | Age | Family_FK
---+----------+------+--------
1 | Jake | 8 | 1
2 | Martin | 7 | 2
3 | Sarah | 10 | 1
4 | Tracy | 12 | 3
where many children (or no children) can be associated with one family. I would like to populate the Oldest column using an UPDATE ... SET ... statement that sets it to the Name and Oldest_Age of the oldest child in each family. Finding the name of each oldest child is a problem that is solved quite well here: How can I SELECT rows with MAX(Column value), DISTINCT by another column in SQL?
However, I don't know how to use the result of this in an UPDATE statement to update the column of an associated table using the h2 database.
The following is ANSI-SQL syntax that solves this problem:
update family
set oldest = (select name
from children c
where c.family_fk = f.id
order by age desc
fetch first 1 row only
)
In h2, I think you would use limit 1 instead of fetch first 1 row only.
EDIT:
For two columns -- alas -- the solution is two subqueries:
update family
set oldest = (select name
from children c
where c.family_fk = f.id
order by age desc
limit 1
),
oldest_age = (select age
from children c
where c.family_fk = f.id
order by age desc
limit 1
);
Some databases (such as SQL Server, Postgres, and Oracle) support lateral joins that can help with this. Also, row_number() can also help solve this problem. Unfortunately, H2 doesn't support this functionality.
Title is confusing I know, I'm just not sure how to word this. Anyway let me describe with a table:
| key | column b | column c |
|-----|----------|----------|
| a | 13 | 2 |
| a | 14 | 2 |
| a | 15 | 1 |
| b | 16 | 2 |
| b | 17 | 2 |
I'd like to select all keys where column c doesn't equal 1, so the select will result in returning only key 'b'
To clarify, my result set should not contain keys that have a row where column c is set to 1. Therefore I'd like a sql query that would return the keys that satisfy the previous statement.
To make my question as clear as possible. From the table above, what I want returned by some sql statement is a result set containing [{b}] based on the fact that key 'a' has at least one row where column c is equal to 1 whereas key 'b' does not have any rows that contain 1 in column c.
SELECT t.[Key]
FROM TableName t
WHERE NOT EXISTS (SELECT 1
FROM TableName
WHERE t.[key] = [key]
AND ColumnC = 1)
GROUP BY t.[Key]
SELECT KEY
FROM WhateverYourTableNameIs
WHERE c <> '1'
I would do this using group by and aggregation:
select [key]
from table t
group by [key]
having sum(case when c = 1 then 1 else 0 end) = 0;
The having clause counts the number of rows that have c = 1. The = 0 says that there are no such rows for a given key.
Elaboration based on other comments:
You asked for ALL keys where column c doesn't equal 1. That is exactly what the query I suggested will give you. The other part of your question so the SELECT will result in returning only key 'b', is ambiguous. The question as asked will give you results from columns A and B. There is nothing in your question to limit the result set. You either need an additional condition to your WHERE clause, or your question is inherently unanswerable.