SQL Server: What does 1 ++ 2 mean?

Question

SQL Server\'s T-SQL syntax seems to allow multiple plus signs in succession:

SELECT 1 + 2 --3
SELECT 1 ++ 2 --3
SELECT 1 ++++++ 2 --3
SELECT 1 + \'2\' --3
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Answer 1

SELECT 1 ++ 2 means 1 plus (+2) which means 3

Same logic for the others 1+(+(+2)) and so on

SELECT '1' + '2' --'12' you are concatenating 2 strings, string '1' and string '2', which results '12'