SQL Server eliminate function call and replace with join - sql-server

Question

I am trying to rewrite the "Query" part by removing the function.
Since the table has more than 800k records, the function is called thrice for all 800k records.
I want to eliminate function and replace with JOIN?
--Function
CREATE FUNCTION [dbo].[MapValue]
(
#ObjCode AS INT,
#ObjName AS VARCHAR(50),
#ObjValue AS INT
)
RETURNS VARCHAR(100)
AS
BEGIN
DECLARE #returnValue AS VARCHAR(100)
SELECT #returnValue = Value FROM dbo.tblMap
WHERE ObjCode = #ObjCode AND ObjName = #ObjName AND ObjValue = #ObjValue
-- Return the result of the function
RETURN #returnValue
END
--Query
SELECT ObjectId, ObjectTypeCode,
dbo.MapValue(4, 'ACode', ACode) AS AType,
dbo.MapValue(4, 'SCode', SCode) AS SCode,
dbo.MapValue(4, 'PCode', PCode) AS PCode
FROM dbo.APoint
WHERE ObjectTypeCode = 1
Here is the query that I came up using JOIN.
Is there any better way to do this? Can we use just ONE join instead of three?
--Modified query
SELECT ObjectId, ObjectTypeCode,
A.Value,
s.Value,
p.Value
FROM dbo.APoint ap
LEFT JOIN tblMap A ON A.ObjCode = 4 AND A.ObjName = 'ACode' AND A.ObjValue = ap.TypeCode
LEFT JOIN tblMap s ON s.ObjCode = 4 AND s.ObjName = 'SCode' AND s.ObjValue = ap.TypeCode
LEFT JOIN tblMap p ON p.ObjCode = 4 AND p.ObjName = 'PCode' AND p.ObjValue = ap.TypeCode
WHERE ObjectTypeCode = 1

Answer 1

You could use case and a single left join:
SELECT ObjectId, ObjectTypeCode,
CASE WHEN map.ObjName = 'ActivityTypeCode' THEN map.Value END AS AType,
CASE WHEN map.ObjName = 'statecode' THEN map.Value END As SCode,
CASE WHEN map.ObjName = 'PriorityCode' THEN map.Value END As PCode
FROM dbo.APoint ap
LEFT JOIN tblMap map ON map.ObjCode = 4
AND map.ObjName IN('ActivityTypeCode', 'statecode', 'PriorityCode')
AND map.ObjValue = ap.ActivityTypeCode
WHERE ObjectTypeCode = 1
GROUP BY ObjectId, ObjectTypeCode