Convert Bit field table to table - sql-server

Question

I have a table showing locations with a BIT column for each tool in use at each location:
CREATE TABLE dbo.[ToolsSelected] (
[LocationID] NVARCHAR(40) NOT NULL,
[Tool1] INTEGER DEFAULT 0 NOT NULL,
[Tool2] INTEGER DEFAULT 0 NOT NULL,
[Tool3] INTEGER DEFAULT 0 NOT NULL,
[Tool4] INTEGER DEFAULT 0 NOT NULL,
PRIMARY KEY ([LocationID])
);
LocID Tool1 Tool2 Tool3 Tool4
----- ----- ----- ----- -----
AZ 0 1 1 0
NY 1 0 1 1
I need to convert this to a table by LocationID indicating which tools at which locations:
CREATE TABLE dbo.[ByLocation] (
[LocationID] NVARCHAR(40) NOT NULL,
[Tool] NVARCHAR(40) NOT NULL, -- Column title of ToolsSelected table
PRIMARY KEY ([LocationID], [Tool])
);
LocID Tool
----- -----
AZ Tool2
AZ Tool3
NY Tool1
NY Tool3
NY Tool4
The idea is that each location can select the tools they need, I then need to query the tools table to get details (versions, etc) for each tool selected. Each location is unique; each tool is unique. Is there a way to do this or a much better implementation?

Answer 1

Here is the answer to the immediate question, given only 4 tools columns:
SELECT LocID = LocationID, Tool
FROM
(
SELECT LocationID, Tool = 'Tool1' FROM dbo.ToolsSelected WHERE Tool1 = 1
UNION ALL
SELECT LocationID, Tool = 'Tool2' FROM dbo.ToolsSelected WHERE Tool2 = 1
UNION ALL
SELECT LocationID, Tool = 'Tool3' FROM dbo.ToolsSelected WHERE Tool3 = 1
UNION ALL
SELECT LocationID, Tool = 'Tool4' FROM dbo.ToolsSelected WHERE Tool4 = 1
) AS x
ORDER BY LocID, Tool;
With 40 columns, you could do the same thing, but along with the desire to generate this dynamically:
DECLARE #sql NVARCHAR(MAX);
SET #sql = N'';
SELECT #sql += '
UNION ALL
SELECT LocationID, Tool = ''' + name + '''
FROM dbo.ToolsSelected WHERE ' + name + ' = 1'
FROM sys.columns WHERE [object_id] = OBJECT_ID('dbo.ToolsSelected')
AND name LIKE 'Tool[0-9]%';
SELECT #sql = N'SELECT LocID = LocationID, Tool
FROM
(' + STUFF(#sql, 1, 17, '') + '
) AS x ORDER BY LocID, Tool;';
PRINT #sql;
-- EXEC sp_executesql #sql;
*BUT*
Storing these as separate columns is a recipe for disaster. So when you add Tool41, Tool42 etc. you have to change the schema then change all your code that passes the column names and 1/0 via parameters etc. Why not represent these as simple numbers, e.g.
CREATE TABLE dbo.LocationTools
(
LocID NVARCHAR(40),
ToolID INT
);
So in the above case you would store:
LocID Tool
----- ----
AZ 2
AZ 3
NY 1
NY 3
NY 4
Now when you pass in the checkboxes they've selected, presumably from the front end you are receiving two values, such as:
LocID: "NY"
Tools: "Tool1, Tool5, Tool26"
If that's about right, then you can populate the table when a user creates or changes their choice, first using a split function to break up the comma-separated list dictated by the checkboxes:
CREATE FUNCTION dbo.SplitTools
(
#ToolList NVARCHAR(MAX)
)
RETURNS TABLE
WITH SCHEMABINDING
AS
RETURN
(
SELECT ToolID = y.i.value('(./text())[1]', 'int')
FROM
(
SELECT x = CONVERT(XML,
'<i>' + REPLACE(REPLACE(#List, ',', '</i><i>'), 'Tool', '')
+ '</i>').query('.')
) AS a CROSS APPLY x.nodes('i') AS y(i)
);
GO
(You forgot to tell us which version of SQL Server you are using - if 2008 or above you could use a table-valued parameter as an alternative to a split function.)
Then a procedure to handle it:
CREATE PROCEDURE dbo.UpdateLocationTools
#LocID NVARCHAR(40),
#Tools NVARCHAR(MAX)
AS
BEGIN
SET NOCOUNT ON;
-- in case they had previously selected tools
-- that are no longer selected, clear first:
DELETE dbo.LocationTools WHERE LocID = #LocID;
INSERT dbo.LocationTools(LocID, ToolID)
SELECT #LocID, ToolID
FROM dbo.SplitTools(#Tools);
END
GO
Now you can add new tool #s without changing schema or code, since your list of checkboxes could also be generated from your data - assuming you have a dbo.Tools table or want to add one. This table could also be used for data integrity purposes (you could put a foreign key on dbo.LocationTools.ToolID).
And you can generate your desired query very simply:
SELECT LocID, Tool = 'Tool' + CONVERT(VARCHAR(12), ToolID)
FROM dbo.LocationTools
ORDER BY LocID, ToolID;
No redundant data, no wide tables with unmanageable columns, and a proper index can even help you search for, say, all locations using Tool3 efficiently...