This is probably a really simple question, but I don't write stored procedures often and I'm a bit mystified...
After doing various stuff, the concluding bit of the SP ends by returning counts or sums from several different tables. The obvious approach is:
select SUM(ThisCol) as ThisResult from...
select SUM(ThatCol) as ThatResult from...
select count(DISTINCT OtherCol) as OtherResult from...
Of course, this creates multiple recordsets - one for each select plus one containing zero. This is a bit silly since each recordset contains exactly one value. I would much prefer to return a single recordset with multiple columns: ThisResult, ThatResult and OtherResult.
Is that possible?
You can use variables
DECLARE #thisResult INT
DECLARE #thatResult INT
DECLARE #otherResult INT
select #thisResult = SUM(ThisCol) as ThisResult from...
select #thatResult = SUM(ThatCol) as ThatResult from...
select #otherResult = count(OtherCol) as OtherResult from...
SELECT #thisResult AS 'thisResult', #thatResult AS 'thatResult', #otherResult AS 'otherResult'
SELECT T1.ThisResult, T2.ThatResult, T3.OtherResult
FROM (select SUM(ThisCol) as ThisResult from...) T1,
(select SUM(ThatCol) as ThatResult from...) T2,
(select count(DISTINCT OtherCol) as OtherResult from...) T3
Because each table contains only 1column & 1 value, you do a cross join of all 3 and put each value in a column in the result table.
If you're using SQL Server, you can select these quantities again as your last statement.
Select ThisResult, ThatResult, OtherResult
You don't have to specify a table
Related
I've been playing around with the sample on Jeff' Server blog to compare two tables to find the differences.
In my case the tables are a backup and the current data. I can get what I want with this SQL statement (simplified by removing most of the columns). I can then see the rows from each table that don't have an exact match and I can see from which table they come.
SELECT
MIN(TableName) as TableName
,[strCustomer]
,[strAddress1]
,[strCity]
,[strPostalCode]
FROM
(SELECT
'Old' as TableName
,[JAS001].[dbo].[AR_CustomerAddresses].[strCustomer]
,[JAS001].[dbo].[AR_CustomerAddresses].[strAddress1]
,[JAS001].[dbo].[AR_CustomerAddresses].[strCity]
,[JAS001].[dbo].[AR_CustomerAddresses].[strPostalCode]
FROM
[JAS001].[dbo].[AR_CustomerAddresses]
UNION ALL
SELECT
'New' as TableName
,[JAS001new].[dbo].[AR_CustomerAddresses].[strCustomer]
,[JAS001new].[dbo].[AR_CustomerAddresses].[strAddress1]
,[JAS001new].[dbo].[AR_CustomerAddresses].[strCity]
,[JAS001new].[dbo].[AR_CustomerAddresses].[strPostalCode]
FROM
[JAS001new].[dbo].[AR_CustomerAddresses]) tmp
GROUP BY
[strCustomer]
,[strAddress1]
,[strCity]
,[strPostalCode]
HAVING
COUNT(*) = 1
This Stack Overflow Answer gives me a much cleaner SQL query but does not tell me from which table the rows come.
SELECT * FROM [JAS001new].[dbo].[AR_CustomerAddresses]
UNION
SELECT * FROM [JAS001].[dbo].[AR_CustomerAddresses]
EXCEPT
SELECT * FROM [JAS001new].[dbo].[AR_CustomerAddresses]
INTERSECT
SELECT * FROM [JAS001].[dbo].[AR_CustomerAddresses]
I could use the first version but I have many tables that I need to compare and I think that there has to be an easy way to add the source table column to the second query. I've tried several things and googled to no avail. I suspect that maybe I'm just not searching for the correct thing since I'm sure it's been answered before.
Maybe I'm going down the wrong trail and there is a better way to compare the databases?
Could you use the following setup to accomplish your goal?
SELECT 'New not in Old' Descriptor, *
FROM
(
SELECT * FROM [JAS001new].[dbo].[AR_CustomerAddresses]
EXCEPT
SELECT * FROM [JAS001].[dbo].[AR_CustomerAddresses]
) a
UNION
SELECT 'Old not in New' Descriptor, *
FROM
(
SELECT * FROM [JAS001].[dbo].[AR_CustomerAddresses]
EXCEPT
SELECT * FROM [JAS001new].[dbo].[AR_CustomerAddresses]
) b
You can't add the table name there because union, except, and intersection all compare all columns. This means you can't differentiate between them by adding the table name to the query. A group by gives you control over what columns are considered in finding duplicates so you can exclude the table name.
To help you with the large number of tables you need to compare you could write a sql query off the metadata tables that hold table names and columns and generate the sql commands dynamically off those values.
Derive one column using table names like below
SELECT MIN(TableName) as TableName
,[strCustomer]
,[strAddress1]
,[strCity]
,[strPostalCode]
,table_name_came
FROM
(SELECT 'Old' as TableName
,[JAS001].[dbo].[AR_CustomerAddresses].[strCustomer]
,[JAS001].[dbo].[AR_CustomerAddresses].[strAddress1]
,[JAS001].[dbo].[AR_CustomerAddresses].[strCity]
,[JAS001].[dbo].[AR_CustomerAddresses].[strPostalCode]
,'[JAS001].[dbo].[AR_CustomerAddresses]' as table_name_came
FROM [JAS001].[dbo].[AR_CustomerAddresses]
UNION ALL
SELECT 'New' as TableName
,[JAS001new].[dbo].[AR_CustomerAddresses].[strCustomer]
,[JAS001new].[dbo].[AR_CustomerAddresses].[strAddress1]
,[JAS001new].[dbo].[AR_CustomerAddresses].[strCity]
,[JAS001new].[dbo].[AR_CustomerAddresses].[strPostalCode]
,'[JAS001new].[dbo].[AR_CustomerAddresses]' as table_name_came
FROM [JAS001new].[dbo].[AR_CustomerAddresses]
) tmp
GROUP BY [strCustomer]
,[strAddress1]
,[strCity]
,[strPostalCode]
,table_name_came
HAVING COUNT(*) = 1
I've got table with few numbers inside (or even empty): #states table (value int)
And I need to make SELECT from another table with WHERE clause by definite column.
This column's values must match one of #states numbers or if #states is empty then accept all values (like there is no WHERE condition for this column).
So I tried something like this:
select *
from dbo.tbl_docs docs
where
docs.doc_state in(iif(exists(select 1 from #states), (select value from #states), docs.doc_state))
Unfortunately iif() can't return subquery resulting dataset. I tried different variations with iif() and CASE but it wasn't successful. How to make this condition?
select *
from dbo.tbl_docs docs
where
(
(select count(*) from #states) > 0
AND
docs.doc_state in(select value from #states)
)
OR
(
(select count(*) from #states)=0
AND 1=1
)
Wouldn't a left join do?
declare #statesCount int;
select #statesCount = count(1) from #states;
select
docs.*
from dbo.tbl_docs docs
left join #states s on docs.doc_state = s.value
where s.value is not null or #statesCount = 0;
In general, whenever your query contains sub-queries, you should stop for five minutes, and think hard about whether you really need a sub-query at all.
And if you've got a server capable of doing that, in many cases it might be better to preprocess the input parameters first, or perhaps use constructs such as MS SQL's with.
select *
from dbo.tbl_docs docs
where exists (select 1 from #states where value = doc_state)
or not exists (select 1 from #state)
I want use the SQL Server IN operator and also set a variable to a column value. Is this possible?
My code is like this:
DECLARE #SubkindId as tinyint;
SELECT NAME FROM SampleTable001 WHERE
Id in (SELECT Id, #SubkindId = Subkind FROM SampleTable002)
ORDER BY Name;
My issue is: I want to set the #SubkindId variable in the inner select statement.
Can It Be Done?
In SQL Server you can't SELECT a result set and SET variables in the same statement (though you can in MySQL). Sorry. But there may be another way to get what you want. Unfortunately, what you want is not completely clear.
Assuming you want to do a SELECT and at the same time return another value into a variable, you have to handle the issue that your query can return multiple rows, so in that case, which one would you want to return into #SubkindId?
Now, I may have misunderstood, and instead of trying to pull the column value into the variable, you instead want to pull only the row where the SubkindId matches the value already in the variable (though you didn't show assigning a value to it first, so this seems less likely).
Please confirm which is the case and answer the above questions, and I can help you more.
In the meantime, I'll try to give you answers for both scenarios.
First, let me mention that I recommend against using the IN() syntax with a subquery returning a list of IDs. It is poor practice in my opinion because it usually demonstrates that the person doesn't really know how to JOIN properly, and as soon as the query gets a little complicated, not only that person but even the best professional SQL Server query writer can get lost (... WHERE x IN (SELECT ... WHERE y IN (SELECT ... WHERE z NOT IN (...))) which soon leads to a serious case of what!?!?!?!. Just use JOINs, and if required, semi-joins (introduced with an EXISTS clause).
Query and Return a Value
If what you really wanted was to get access to the values that the SELECT statement found while doing its join, it might look something like this:
DECLARE #KindsAndSubkinds TABLE (
Name varchar(100),
SubkindId tinyint
);
INSERT #KindsAndSubkinds
SELECT
T1.Name,
T2.SubkindId
FROM
dbo.SampleTable001 T1
INNER JOIN dbo.SampleTable002 T2
ON T1.Id = T2.Id
SELECT DISTINCT Name
FROM #KindsAndSubkinds
ORDER BY Name;
-- Now you can something with the `SubkindId`s in the #KindsAndSubkinds table variable.
Just Query
If you really were just trying to query rather than return a value, this is what I would recommend:
DECLARE #SubkindId as tinyint;
SET #SubkindId = 5;
SELECT
T1.Name
FROM
dbo.SampleTable001 T1
INNER JOIN dbo.SampleTable002 T2
ON T1.Id = T2.Id
WHERE
T2.Subkind = #SubkindId
ORDER BY
T1.Name;
If there are multiple rows in SampleTable002 but you don't want them in the result set, then:
SELECT
T1.Name
FROM
dbo.SampleTable001 T1
WHERE
EXISTS (
-- This semi-join requires at least one row to exist
-- but doesn't increase the row count
SELECT *
FROM dbo.SampleTable002 T2
WHERE
T1.Id = T2.Id
AND T2.Subkind = #SubkindId
)
ORDER BY
T1.Name;
I hope this helps.
Do it like this:
DECLARE #SubkindId as tinyint
SELECT [NAME]
FROM SampleTable001
WHERE Id in (SELECT Id
from SampleTable002
WHERE Subkind=#SubkindId)
order by [Name]
or by using JOIN
DECLARE #SubkindId as tinyint
SELECT [NAME]
FROM SampleTable001 a
INNER JOIN SampleTable002 b
ON a.id = b.id
WHERE b.Subkind=#SubkindId
order by [Name]
Debugging an app which queries SQL Server 05, can't change the query but need to optimise things.
Running all the selects seperately are quick <1sec, eg: select * from acscard, select id from employee... When joined together it takes 50 seconds.
Is it better to set uninteresting accesscardid fields to null or to '' when using EXISTS?
SELECT * FROM ACSCard
WHERE NOT EXISTS
( SELECT Id FROM Employee
WHERE Employee.AccessCardId = ACSCard.acs_card_number )
AND NOT EXISTS
( SELECT Id FROM Visit
WHERE Visit.AccessCardId = ACSCard.acs_card_number )
ORDER by acs_card_id
Do you have indexes on Employee.AccessCardId, Visit.AccessCardId, and ACSCard.acs_card_number?
The SELECT clause is not evaluated in an EXISTS clause. This:
WHERE EXISTS(SELECT 1/0
FROM EMPLOYEE)
...should raise an error for dividing by zero, but it won't. But you need to put something in the SELECT clause for it to be a valid query - it doesn't matter if it's NULL or a zero length string.
In SQL Server, NOT EXISTS (and NOT IN) are better than the LEFT JOIN/IS NULL approach if the columns being compared are not nullable (the values on either side can not be NULL). The columns compared should be indexed, if they aren't already.
Is there a better solution to the problem of looking up multiple known IDs in a table:
SELECT * FROM some_table WHERE id='1001' OR id='2002' OR id='3003' OR ...
I can have several hundreds of known items. Ideas?
SELECT * FROM some_table WHERE ID IN ('1001', '1002', '1003')
and if your known IDs are coming from another table
SELECT * FROM some_table WHERE ID IN (
SELECT KnownID FROM some_other_table WHERE someCondition
)
The first (naive) option:
SELECT * FROM some_table WHERE id IN ('1001', '2002', '3003' ... )
However, we should be able to do better. IN is very bad when you have a lot of items, and you mentioned hundreds of these ids. What creates them? Where do they come from? Can you write a query that returns this list? If so:
SELECT *
FROM some_table
INNER JOIN ( your query here) filter ON some_table.id=filter.id
See Arrays and Lists in SQL Server 2005
ORs are notoriously slow in SQL.
Your question is short on specifics, but depending on your requirements and constraints I would build a look-up table with your IDs and use the EXISTS predicate:
select t.id from some_table t
where EXISTS (select * from lookup_table l where t.id = l.id)
For a fixed set of IDs you can do:
SELECT * FROM some_table WHERE id IN (1001, 2002, 3003);
For a set that changes each time, you might want to create a table to hold them and then query:
SELECT * FROM some_table WHERE id IN
(SELECT id FROM selected_ids WHERE key=123);
Another approach is to use collections - the syntax for this will depend on your DBMS.
Finally, there is always this "kludgy" approach:
SELECT * FROM some_table WHERE '|1001|2002|3003|' LIKE '%|' || id || '|%';
In Oracle, I always put the id's into a TEMPORARY TABLE to perform massive SELECT's and DML operations:
CREATE GLOBAL TEMPORARY TABLE t_temp (id INT)
SELECT *
FROM mytable
WHERE mytable.id IN
(
SELECT id
FROM t_temp
)
You can fill the temporary table in a single client-server roundtrip using Oracle collection types.
We have a similar issue in an application written for MS SQL Server 7. Although I dislike the solution used, we're not aware of anything better...
'Better' solutions exist in 2008 as far as I know, but we have Zero clients using that :)
We created a table valued user defined function that takes a comma delimited string of IDs, and returns a table of IDs. The SQL then reads reasonably well, and none of it is dynamic, but there is still the annoying double overhead:
1. Client concatenates the IDs into the string
2. SQL Server parses the string to create a table of IDs
There are lots of ways of turning '1,2,3,4,5' into a table of IDs, but the Stored Procedure which uses the function ends up looking like...
CREATE PROCEDURE my_road_to_hell #IDs AS VARCHAR(8000)
AS
BEGIN
SELECT
*
FROM
myTable
INNER JOIN
dbo.fn_split_list(#IDs) AS [IDs]
ON [IDs].id = myTable.id
END
The fastest is to put the ids in another table and JOIN
SELECT some_table.*
FROM some_table INNER JOIN some_other_table ON some_table.id = some_other_table.id
where some_other_table would have just one field (ids) and all values would be unique