MariaDB 10.6

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SET @s = 'ManualBanking-BankDeposit-350-1006590343--INTERNAL_A';
SELECT @s;

@s

ManualBanking-BankDeposit-350-1006590343--INTERNAL_A

SELECT SUBSTRING_INDEX(@s, '-', -3);

SUBSTRING_INDEX(@s, '-', -3)

1006590343--INTERNAL_A

SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(@s, '-', -3), '-', 1);

SUBSTRING_INDEX(SUBSTRING_INDEX(@s, '-', -3), '-', 1)

1006590343