best way to delete and reinsert data to database - sql

Question

so i have a catalog inside a sql server table, i need to be refreshing every 12 hours this catalog, what's the correct way into doing this?
i have been doing a simple delete and afterwards a bulkcopy of the updated data, but im afraid that another process is using this table and might break something.
Cheers,

Answer 1

You could use MERGE feature. It is available in MS SQL Server 2008+, and also add a try/catch - transaction handling. Try following example:
CREATE TABLE #Temp1
(
Id INT IDENTITY PRIMARY KEY
,Description NVARCHAR(20)
)
CREATE TABLE #Temp2
(
Id INT IDENTITY PRIMARY KEY
,Description NVARCHAR(20)
)
INSERT INTO #Temp1 VALUES ('Example1'), ('Example2'), ('');
INSERT INTO #Temp2 VALUES ('Example1'), ('Example4'), ('Example5');
--First values:
SELECT Id, Description FROM dbo.#Temp1;
SELECT Id, Description FROM dbo.#Temp2;
BEGIN TRY
BEGIN TRANSACTION;
--MERGE statement:
--#Temp1 will be our Target and #Temp2 our Source
MERGE dbo.#Temp1 AS target
USING (SELECT Id, Description FROM #Temp2) AS source
ON (target.Id = source.Id)
--When rows matched and description from Target will be '', then the delete will happen
WHEN MATCHED AND target.Description = ''
THEN DELETE
--When rows matched (by their Id, seen previously), then the update will happen:
WHEN MATCHED
THEN UPDATE SET target.Description = source.Description
OUTPUT $action;
COMMIT TRANSACTION;
END TRY
BEGIN CATCH
RAISERROR('<<Transaction uncommited. Rolling back transaction',10,1);
ROLLBACK TRANSACTION;
END CATCH
--Final values:
SELECT Id, Description FROM dbo.#Temp1;
SELECT Id, Description FROM dbo.#Temp2;
DROP TABLE #Temp1;
DROP TABLE #Temp2;