MySQL: Select query using WHERE IN () with variables on the basis of conditions

For my MySQL PROCEDURE, I have a select query statement using WHERE IN (...) clause, for which I need some conditional inputs/variables.

example:

SELECT * FROM test_table tt WHERE tt.section IN ('A', 'B', 'C');

SELECT * FROM test_table tt WHERE tt.section IN ('A', 'B', 'D');

SELECT * FROM test_table tt WHERE tt.section IN ('A','C');

SELECT * FROM test_table tt WHERE tt.section IN ('A', 'B', 'C', 'D');

How can I achieve this using a single query?

Note: This select query statement is inside mySQL PROCEDURE.

I'm looking for something like this:

SET @ABC = '"A", "B", "C"';
SET @ABCD = '"A", "B", "C", "D"';
SET @AC = '"A", "B", "C", "D"';

SET @IN_CLAOUSE_VARIABLES = NULL;

IF (<CONDITION 1>) THEN
    SET @IN_CLAOUSE_VARIABLES = @ABC;
  ELSEIF (<CONDITION 2>) THEN
    SET @IN_CLAOUSE_VARIABLES = @ABCD;
  ELSE
    SET @IN_CLAOUSE_VARIABLES = @AC;
END IF:

SELECT * FROM test_table tt WHERE tt.section IN (@IN_CLAOUSE_VARIABLES);

Solution

SET @ABC = 'A,B,C';
SET @ABCD = 'A,B,C,D';
SET @AC = 'A,C';

SET @IN_CLAOUSE_VARIABLES = NULL;

IF (<CONDITION 1>) THEN
    SET @IN_CLAOUSE_VARIABLES = @ABC;
  ELSEIF (<CONDITION 2>) THEN
    SET @IN_CLAOUSE_VARIABLES = @ABCD;
  ELSE
    SET @IN_CLAOUSE_VARIABLES = @AC;
END IF:

SELECT * FROM test_table tt WHERE FIND_IN_SET(tt.section, @IN_CLAOUSE_VARIABLES);

tt.section must NOT contain commas and not need to be quoted with ". I.e. it may be 'A' (will be found in all variants), 'D' (only when <CONDITION 1> is false and <CONDITION 2> is true) or 'X' (never).