Update README.md

Author: ronascentes

README.md

@@ -8,19 +8,26 @@ Explicit validation to ensure the object, variable or component is in the expect
 You might want to check if a object already exist before creating it. You can use this patterns for table, procedures or any object in the database.
 ```sql
 IF EXISTS (SELECT [object_id] FROM tempdb.sys.objects (NOLOCK) WHERE [object_id] = OBJECT_ID('tempdb.dbo.#<table_name>'))      
-	DROP TABLE #<table_name>;
+    DROP TABLE #<table_name>;
 ```
 
 ### Check if database exists
 Does the database exists and is it up and running?
 ```sql
 IF EXISTS (SELECT CASE WHEN DATABASEPROPERTYEX(name, 'Status') = 'ONLINE' THEN 1 END FROM master.dbo.sysdatabases WHERE name = <db_name>)
-	PRINT N'<db_name> is available';
+    PRINT N'<db_name> is available';
 ```
 ### Check if is primary node
-Check if the current replica of a Availability Group is the primary one.  
+Check if the current replica of a Availability Group is the primary one. First check if AG is enabled. 
 ```sql
-IF sys.fn_hadr_is_primary_replica ('<db_name>') = 
+IF (SELECT SERVERPROPERTY('IsHadrEnabled')) = 1
+BEGIN
+    IF sys.fn_hadr_is_primary_replica ( @DatabaseName ) = 1 
+    BEGIN
+        PRINT N'Database is not the primary';
+    END;
+END;
+
 ```
 
 ### Null or empty
@@ -67,5 +74,31 @@ END CATCH;
 ### Use the database context
 
 ## Data manipulation
+### Deleting a large number of rows
+It´s a script you can use to purge a large number of rows of a given table. You can start/stop the script freely, it won’t hurt anything. It´s setup to delete 1000 records per loop, but you can change this value based in your needs. The most important thing is to use a loop value which does not cause T-LOG contention.  
 ```sql
+BEGIN  
+    SET NOCOUNT, XACT_ABORT ON;
+    DECLARE @ErrorMessage NVARCHAR(4000), @rows INT;  
+    BEGIN TRY
+        SET @rows = 1;  
+  	WHILE (@rows > 0)  
+  	BEGIN  
+   	    BEGIN TRANSACTION  
+                -- purge data older than 90 days 
+                DELETE TOP(1000) FROM [dbo].[<table_name>] WHERE [LastUpdated] <= DATEADD(M, -3, GETDATE());
+    		SET @rows = @@ROWCOUNT;  
+            COMMIT TRANSACTION;  
+        END;  
+    END TRY  
+    BEGIN CATCH  
+        SELECT @ErrorMessage = ERROR_MESSAGE();   
+	PRINT @ErrorMessage;  
+	IF (XACT_STATE()) = -1  
+	    ROLLBACK;  
+	IF (XACT_STATE()) = 1  
+	    COMMIT;   
+	    THROW;  
+    END CATCH;
+END;
 ```