I got around 18 db's. All these db's have the same structure. I want to query all these db's once to get my results.
Example:
ShopA
ShopB
ShopC
These db's got all the table article (and also the same rows).
How do I get all articles in one result with a WHERE?
I thought:
select *
from shopa.dbo.article
shopb.dbo.article
shopc.dbo.article
where color = 'red'
Did someone got an idea?
Have you considered doing a UNION ALL?
So something like:
SELECT 'a' AS Shop, *
FROM shopa.dbo.article
WHERE color = 'red'
UNION ALL
SELECT 'b' AS Shop, *
FROM shopb.dbo.article
WHERE color = 'red'
UNION ALL
SELECT 'c' AS Shop, *
FROM shopc.dbo.article
WHERE color = 'red'
Or, with a CTE (if you RDBMS supports it)
;WITH allstores AS (
SELECT 'a' AS Shop, *
FROM shopa.dbo.article
UNION ALL
SELECT 'b' AS Shop, *
FROM shopb.dbo.article
UNION ALL
SELECT 'c' AS Shop, *
FROM shopc.dbo.article
)
SELECT *
FROM allstores
WHERE color = 'red'
you could use UNION
if you can simply select the db names you could also use a cursor select with OPENQUERY on a dynamically created string insert into a temp table and select from that
You can create a View wich is populated from your select as this:
CREATE VIEW view_name AS
SELECT * FROM shopa.dbo.article
UNION
SELECT * FROM shopb.dbo.article
UNION
SELECT * FROM shopc.dbo.article
Then you can try to run a query by the View
Select * from view_name
where color = 'red'
Then if you want write another query with another condition, you don't write another big query with union or other code.
You can just write a query on a VIEW
Related
Got a tricky one today (Might even just be me):
I have 8 Linked SQL 2012 servers configured to my main SQL server and I need to create table views so that I can filter all these combined table results only using one where clause, currently I use UNION because they all have the same table structures.
Currently my solution looks as follows:
SELECT * FROM [LinkedServer_1].[dbo].[Table] where value = 'xxx'
UNION
SELECT * FROM [LinkedServer_2].[dbo].[Table] where value = 'xxx'
UNION
SELECT * FROM [LinkedServer_3].[dbo].[Table] where value = 'xxx'
UNION
SELECT * FROM [LinkedServer_4].[dbo].[Table] where value = 'xxx'
UNION
SELECT * FROM [LinkedServer_5].[dbo].[Table] where value = 'xxx'
UNION
SELECT * FROM [LinkedServer_6].[dbo].[Table] where value = 'xxx'
UNION
SELECT * FROM [LinkedServer_7].[dbo].[Table] where value = 'xxx'
UNION
SELECT * FROM [LinkedServer_8].[dbo].[Table] where value = 'xxx'
As you can see this is becoming quite ugly because I have a select statement and where clause for each linked server and would like to know if there was a simpler way of doing this!
Appreciate the feedback.
Brakkie101
Instead of using views, you can use inline table-valued functions (a view with parameters). It will not save initial efforts for creating the queries, but could save some work in the future:
CREATE FUNCTION [dbo].[fn_LinkedSever] (#value NVARCHAR(128))
AS
RETURNS TABLE
AS
RETURN
(
SELECT * FROM [LinkedServer_1].[dbo].[Table] where value = #value
UNION
SELECT * FROM [LinkedServer_2].[dbo].[Table] where value = #value
UNION
SELECT * FROM [LinkedServer_3].[dbo].[Table] where value = #value
UNION
SELECT * FROM [LinkedServer_4].[dbo].[Table] where value = #value
UNION
SELECT * FROM [LinkedServer_5].[dbo].[Table] where value = #value
UNION
SELECT * FROM [LinkedServer_6].[dbo].[Table] where value = #value
UNION
SELECT * FROM [LinkedServer_7].[dbo].[Table] where value = #value
UNION
SELECT * FROM [LinkedServer_8].[dbo].[Table] where value = #value
);
Also, if possible, use UNION ALL instead of UNION.
I am approaching this issue from a non DBA perspective, as in I do not have permissions to create new tables for the database. I am trying to work around this by using a subquery in Oracle kind of like this sudo code:
With temptable as ('col1name', 'col2name', 1,'a',2,'b')
Select * from temptable where col1name = 1
With the temptable looking like
Col1name | Col2name
1 a
2 b
And the output being row 1. I know it is not the easiest way to do it, but it is all I can think of to accomplish my task until I can get the admin to approve a new table. I have searched a lot but I can't find an answer. Is there a simple way to define temporary table data like this?
I would just do this as:
with temptable as (
select 1 as col1name, 'a' col2name from dual union all
select 2, 'b' from dual
)
Select *
from temptable
where col1name = 1;
As an alternative to a CTE (common table expresssion) as suggested by Gordon, you can also use a query as an old-school inline view.
For example:
SELECT tt.col1name
, tt.col2name
FROM ( SELECT 1 AS col1name, 'a' AS col2name FROM DUAL
UNION ALL SELECT 2, 'b' FROM DUAL
UNION ALL SELECT 3, 'c' FROM DUAL
) tt
WHERE tt.col1name = 1
ORDER
BY tt.col1name
I have a script that extracts transactions and their details from a database. But my users complain that the file size being generated is too large, and so they asked for certain transactions to be just summed up/consolidated instead if they are of a certain classification, say Checking Accounts. That means there should only be one line in the result set named "Checking" which contains the sum of all transactions under Checking Accounts. Is there a way for an SQL script to go like:
CASE
WHEN Acct_class = 'Checking'
then sum(tran_amount)
ELSE tran_amount
END
I already have the proper GROUP BY and ORDER BY statements, but I can't seem to get my desired output. There is still more than one "Checking" line in the result set. Any ideas would be very much appreciated.
Try This,
Select sum(tran_amount) From tran_amount Where Acct_class = 'Checking'
You can try to achieve this using UNION ALL
SELECT tran_amount, .... FROM table WHERE NOT Acct_class = 'Checking'
UNION ALL
SELECT SUM(tran_amount), .... FROM table WHERE Acct_class = 'Checking' GROUP BY Acct_class, ...;
hi you can try below sql
select account_class,
case when account_class = 'saving' then listagg(trans_detail, ',') within group (order by emp_name) -- will give you all details transactions
when account_class = 'checking' then to_char(sum(trans_detail)) -- will give you only sum of transactions
end as trans_det from emp group by account_class;
Or, if your desired output is getting either the sum, either the actual column value based on another column value, the solution would be to use an analytical function to get the sum together with the actual value:
select
decode(acct_class, 'Checking', tran_amount_sum, tran_amount)
from (
select
sum(tran_amount) over (partition by acct_class) as tran_amount_sum,
tran_amount,
acct_class
from
YOUR_TABLE
)
You can try something like the following, by keeping single rows for some classes, and aggregating for some others:
with test (id, class, amount) as
(
select 1, 'a' , 100 from dual union all
select 2, 'a' , 100 from dual union all
select 3, 'Checking', 100 from dual union all
select 4, 'Checking', 100 from dual union all
select 5, 'c' , 100 from dual union all
select 6, 'c' , 100 from dual union all
select 7, 'c' , 100 from dual union all
select 8, 'd' , 100 from dual
)
select sum(amount), class
from test
group by case
when class = 'Checking' then null /* aggregates elements of class 'b' */
else id /* keeps elements of other classes not aggregated */
end,
class
I want to define a SQL-command like this:
SELECT * FROM WOMAN
UNION
SELECT * FROM MEN
I tried to define this with the following code sequence in Ruby + Sequel:
require 'sequel'
DB = Sequel::Database.new()
sel = DB[:women].union(DB[:men])
puts sel.sql
The result is (I made some pretty print on the result):
SELECT * FROM (
SELECT * FROM `women`
UNION
SELECT * FROM `men`
) AS 't1'
There is an additional (superfluous?) SELECT.
If I define multiple UNION like in this code sample
sel = DB[:women].union(DB[:men]).union(DB[:girls]).union(DB[:boys])
puts sel.sql
I get more superfluous SELECTs.
SELECT * FROM (
SELECT * FROM (
SELECT * FROM (
SELECT * FROM `women`
UNION
SELECT * FROM `men`
) AS 't1'
UNION
SELECT * FROM `girls`
) AS 't1'
UNION
SELECT * FROM `boys`
) AS 't1'
I detected no problem with it up to now, the results seem to be the same.
My questions:
Is there a reason for the additional selects (beside sequel internal procedures)
Can I avoid the selects?
Can I get problems with this additional selects? (Any Performance issue?)
The reason for the extra SELECTs is so code like DB[:girls].union(DB[:boys]).where(:some_column=>1) operates properly. You can use DB[:girls].union(DB[:boys], :from_self=>false) to not wrap it in the extra SELECTs, as mentioned in the documentation.
I have a set of tables that are logically one table split into pieces for performance reasons. I need to write a query that effectively joins all the tables together so I use a single where clause of the result. I have successfully used a UNION on the result of using the WHERE clause on each subtable explicitly as in the following
SELECT * FROM FRED_1 WHERE CHARLIE = 42
UNION
SELECT * FROM FRED_2 WHERE CHARLIE = 42
UNION
SELECT * FROM FRED_3 WHERE CHARLIE = 42
but as there are ten separate subtables updating the WHERE clause each time is a pain. What I want is something like this
SELECT *
FROM (
SELECT * FROM FRED_1
UNION
SELECT * FROM FRED_2
UNION
SELECT * FROM FRED_3)
WHERE CHARLIE = 42
If it makes a difference the query needs to run against a DB2 database.
Here is a more comprehensive (sanitised) version of what I need to do.
select *
from ( select * from FRD_1 union select * from FRD_2 union select * from FRD_3 ) as FRD,
( select * from REQ_1 union select * from REQ_2 union select * from REQ_3 ) as REQ,
( select * from RES_1 union select * from RES_2 union select * from RES_3 ) as RES
where FRD.KEY1 = 123456
and FRD.KEY1 = REQ.KEY1
and FRD.KEY1 = RES.KEY1
and REQ.KEY2 = RES.KEY2
NEW INFORMATION:
It looks like the problem has more to do with the number of fields in the union than anything else. If I greatly restrict the fields I can get most of the syntax variations below working. Unfortunately, restricting the fields so much means the resulting query, while potentially useful, is not giving me the result I wanted. I've managed to get an additional 3 fields from one of the tables in addition to the 2 keys. Any more than that and the query fails.
I believe you have to give a name to your subquery result. I don't know db2 so I'm taking a shot in the dark, but I know this works on several other platforms.
SELECT *
FROM (
SELECT * FROM FRED_1
UNION
SELECT * FROM FRED_2
UNION
SELECT * FROM FRED_3) AS T1
WHERE CHARLIE = 42
If the logical implementation is a single table but the physical implementation is multiple tables then how about creating a view that defines the logical model.
CREATE VIEW VW_FRED AS
SELECT * FROM FRED_1
UNION
SELECT * FROM FRED_2
UNION
SELECT * FROM FRED_3
then it's a simple matter of
SELECT * FROM VW_FRED WHERE CHARLIE = 42
Again, I'm not familiar with db2 syntax but this gives you the general idea.
with
FRD as ( select * from FRD_1 union select * from FRD_2 union select * from FRD_3 ),
REQ as ( select * from REQ_1 union select * from REQ_2 union select * from REQ_3 ),
RES as ( select * from RES_1 union select * from RES_2 union select * from RES_3 )
SELECT * from FRD, REQ, RES
WHERE FRD.KEY1 = 123456
and FRD.KEY1 = REQ.KEY1
and FRD.KEY1 = RES.KEY1
and REQ.KEY2 = RES.KEY2
I'm not familiar with DB2 syntax but why aren't you doing this as an INNER JOIN or LEFT JOIN?
SELECT *
FROM FRED_1
INNER JOIN FRED_2
ON FRED_1.Charlie = FRED_2.Charlie
INNER JOIN FRED_3
ON FRED_1.Charlie = FRED_3.Charlie
WHERE FRED_1.Charlie = 42
If the values don't exist in FRED_2 or FRED_3 then use a LEFT/OUTER JOIN. I'm assuming that FRED_1 is a master table, and if a record exists then it will be in this table.
maybe:
SELECT * FROM
(select * from FRD_1
union
select * from FRD_2
union
select * from FRD_3) FRD
INNER JOIN (select * from REQ_1 union select * from REQ_2 union select * from REQ_3) REQ
on FRD.KEY1 = REQ.KEY1
INNER JOIN (select * from RES_1 union select * from RES_2 union select * from RES_3) RES
on FRD.KEY1 = RES.KEY1
WHERE FRD.KEY1 = 123456 and REQ.KEY2 = RES.KEY2