I am displaying records on a page, and I need a way for the user to select a subset of those records to be displayed on another page. These records aren't stored anywhere the are a dynamically generated thing.
What is the best way to in sql to say where a uniqueid is in this list of ids not in a table etc. I know I could dynamically construct the sql with a bunch of ors, but that seems like a hack. anyone else have any suggestions?
this is the best source:
http://www.sommarskog.se/arrays-in-sql.html
create a split function, and use it like:
SELECT
*
FROM YourTable y
INNER JOIN dbo.splitFunction(@Parameter) s ON y.ID=s.Value
I prefer the number table approach
For this method to work, you need to do this one time table setup:
SELECT TOP 10000 IDENTITY(int,1,1) AS Number
INTO Numbers
FROM sys.objects s1
CROSS JOIN sys.objects s2
ALTER TABLE Numbers ADD CONSTRAINT PK_Numbers PRIMARY KEY CLUSTERED (Number)
Once the Numbers table is set up, create this function:
CREATE FUNCTION [dbo].[FN_ListToTable]
(
@SplitOn char(1) --REQUIRED, the character to split the @List string on
,@List varchar(8000)--REQUIRED, the list to split apart
)
RETURNS TABLE
AS
RETURN
(
----------------
--SINGLE QUERY-- --this will not return empty rows
----------------
SELECT
ListValue
FROM (SELECT
LTRIM(RTRIM(SUBSTRING(List2, number+1, CHARINDEX(@SplitOn, List2, number+1)-number - 1))) AS ListValue
FROM (
SELECT @SplitOn + @List + @SplitOn AS List2
) AS dt
INNER JOIN Numbers n ON n.Number < LEN(dt.List2)
WHERE SUBSTRING(List2, number, 1) = @SplitOn
) dt2
WHERE ListValue IS NOT NULL AND ListValue!=''
);
GO
You can now easily split a CSV string into a table and join on it:
select * from dbo.FN_ListToTable(',','1,2,3,,,4,5,6777,,,')
OUTPUT:
ListValue
-----------------------
1
2
3
4
5
6777
(6 row(s) affected)
Your can pass in a CSV string into a procedure and process only rows for the given IDs:
SELECT
y.*
FROM YourTable y
INNER JOIN dbo.FN_ListToTable(',',@GivenCSV) s ON y.ID=s.ListValue
You can use the solution Joel Spolsky recently gave for this problem.
SELECT * FROM MyTable
WHERE ',' + 'comma,separated,list,of,words' + ','
LIKE '%,' + MyTable.word + ',%';
That solution is clever but slow. The better solution is to split the comma-separated string, and construct a dynamic SQL query with the IN() predicate, adding a query parameter placeholder for each element in your list of values:
SELECT * FROM MyTable
WHERE word IN ( ?, ?, ?, ?, ?, ?, ?, ? );
The number of placeholders is what you have to determine when you split your comma-separated string. Then pass one value from that list per parameter.
If you have too many values in the list and making a long IN() predicate is unwieldy, then insert the values to a temporary table, and JOIN against your main table:
CREATE TEMPORARY TABLE TempTableForSplitValues (word VARCHAR(20));
...split your comma-separated list and INSERT each value to a separate row...
SELECT * FROM MyTable JOIN TempTableForSplitValues USING (word);
Also see many other similar questions on SO, including:
