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sql - Generate serial number in mysql query

I have a table: student_marks

marks
-----
  44
  55
  64
  98
  76

Expected output:

serial_number|marks
--------------------
  1          | 44
  2          | 55
  3          | 64
  4          | 98
  5          | 76

Using mysql user defined variables, it could be done using query:

 set  @a:=0;select @a:=@a+1 serial_number, marks from student_marks;

Is there any way to achieve this in msyql without using user defined variables?

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Based on your reasons for not wanting to use user defined variables as wanting to avoid having 2 queries, one for inializing and one to use it you could use the following:

SELECT  @a:=@a+1 serial_number, 
        marks 
FROM    student_marks,
        (SELECT @a:= 0) AS a;

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