concatenation against INTEGER values

There is some differences between Plus operator's concatenation and CONCAT() function.

SELECT CONCAT(1, 2, 3, 4) AS IntegersCONCAT
SELECT 1+2+3+4 as IntegersPlusOperation

Output:

IntegersCONCAT  
1234

IntegersPlusOperation  
10

Plus operator will do the addition operation against the integer operands; where as CONACT considers each operand as Strings.. so it resulted '1234' as output