EXISTS simply tests whether the inner query returns any row. If it does, then the outer query proceeds.

If not, the outer query does not execute, and the entire SQL statement returns nothing.

The general syntax for the Exist statement is

SELECT "column_name1"
FROM "table_name1"
WHERE EXISTS
(SELECT *
FROM "table_name2"
WHERE "condition");

So we can get any kind of validation by using this clause in our SQL query.

ALTER PROC [dbo].[uspSaveNudgeForFriend]
	 @AccessToken VARCHAR(50)
	,@Message VARCHAR(500)
	,@Url VARCHAR(500)
	,@LocationID BIGINT
	,@TargetUserID BIGINT
	,@DaysTillExpire INT
	,@HoursTillExpire INT
	,@IsCompleted BIT
	,@IsDeleted BIT
	,@IsExpired BIT
	,@IsDelivered BIT
AS
	IF EXISTS(SELECT 1 FROM [dbo].[User] WHERE AccessToken = @AccessToken AND IsDeleted = 0)
	BEGIN
		DECLARE @CreatedDate AS DATETIME = GETDATE()
		DECLARE @ExpiryDate AS DATETIME = (SELECT DATEADD(DAY, @DaysTillExpire, @CreatedDate))
		SET @ExpiryDate = (SELECT DATEADD(HOUR, @HoursTillExpire, @ExpiryDate))

		INSERT INTO [dbo].[Nudge]
		(
			 [Message]
			,[Url]
			,[LocationID]
			,[TargetUserID]
			,[DaysTillExpire]
			,[HoursTillExpire]
			,[IsCompleted]
			,[IsDeleted]
			,[ExpiryDate]
			,[IsExpired]
			,[IsDelivered]
			,[CreatedBy]
			,[CreatedDate])
		VALUES
		(
			 @Message
			,@Url
			,@LocationID 
			,@TargetUserID 
			,@DaysTillExpire 
			,@HoursTillExpire 
			,@IsCompleted 
			,@IsDeleted 
			,@ExpiryDate
			,@IsExpired 
			,@IsDelivered 
			,(SELECT ID FROM [dbo].[User] WHERE AccessToken = @AccessToken) 
			,@CreatedDate
		)

		SELECT 1
	END
	ELSE
	BEGIN
		SELECT 2
	END