SQL SERVER 2012 IF EXIST and IF NOT EXIST - mysql

Question

I am trying to write a query to check if a meter exist then do an update, it not do an insert to the monthly data table! The problem is I am confused about the syntax and I am not sure how to do it!
This is the database design. Let's say I have the meter number 2012345 how do I do that? Thank you

Answer 1

In SQL Server (using just name as a demo, you'll of course want more fields)
MERGE meters AS target
USING (SELECT '2012345') AS source (meternumber)
ON (target.meternumber = source.meternumber)
WHEN MATCHED THEN
UPDATE SET name='MeterUpdate#1', meternumber=source.meternumber
WHEN NOT MATCHED THEN
INSERT (name, meternumber) VALUES ('MeterInsert#1', source.meternumber);
An SQLfiddle to test with.
In MySQL, create a unique index on meters(meternumber);
CREATE UNIQUE INDEX bop ON meters(meternumber);
then insert/update using;
INSERT INTO meters (name, meternumber) VALUES ('MeterInsert#1', '2012345')
ON DUPLICATE KEY UPDATE name='MeterUpdate#1', meternumber='2012345';
Another SQLfiddle.

Answer 2

SQL Server has MERGE http://msdn.microsoft.com/en-us/library/bb522522(v=sql.105).aspx that you can use as an UPSERT. Here's an example copied from the docs (Example A):
MERGE dbo.FactBuyingHabits AS Target
USING (SELECT CustomerID, ProductID, PurchaseDate FROM dbo.Purchases) AS Source
ON (Target.ProductID = Source.ProductID AND Target.CustomerID = Source.CustomerID)
WHEN MATCHED THEN
UPDATE SET Target.LastPurchaseDate = Source.PurchaseDate
WHEN NOT MATCHED BY TARGET THEN
INSERT (CustomerID, ProductID, LastPurchaseDate)
VALUES (Source.CustomerID, Source.ProductID, Source.PurchaseDate)
OUTPUT $action, Inserted.*, Deleted.*;