title: TSQL Create trigger with transaction and try catch block
body: <p>i have some questions about a transaction in the trigger, for which I haven't found an answer yet.</p>
  
  <pre><code>CREATE TRIGGER A_AI ON A
  AFTER INSERT AS
  
      BEGIN TRY --is the try block 1 transaction ? or do I have to begin the transaction?
  
          --BEGIN TRAN: may I start the transaction like this?
          -- SOME DANGEROUS OPERATIONS
  
          COMMIT --has this sense here?
      END TRY
      BEGIN CATCH --silent catch no rasing errors.
          ROLLBACK TRANSACTION -- does it work without BEGIN TRANSACTION? if so, is it the whole try block?
      END CATCH
  
  GO
  </code></pre>