MySQL 8.0

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create table t_object(Object_ID int, Name varchar(50))
create table t_operation(OperationID int, Object_ID int,  Name varchar(50))
create table t_operationtag(PropertyID int, ElementID int, Property varchar(50), VALUE varchar(50))
INSERT INTO t_object(Object_ID,Name)
VALUES
   (1,'myClass1'),
   (2,'myClass2'),
   (3,'myClass3');
INSERT INTO t_operation(OperationID,Object_ID,Name)
VALUES
   (1,1,'class1Operation1'),
   (2,1,'class1Operation2'),
   (3,1,'class1Operation3'),
   (4,2,'class2Operation1'),
   (5,2,'class2Operation2'),
   (6,2,'class2Operation3'),
   (7,3,'class3Operation1'),
   (8,3,'class3Operation2'),
   (9,3,'class3Operation3');
INSERT INTO t_operationtag(PropertyID,ElementID,Property,VALUE)
VALUES
   (1,1,'Calls','class2Operation1,class2Operation2,class2Operation3'),
   (2,2,'Calls','class3Operation1'),
   (3,3,'Calls','class3Operation2'),
   (4,4,'Calls','class3Operation3'),
   (5,5,'Calls','class1Operation1'),
   (6,6,'Calls','class1Operation2,class1Operation3'),
   (7,7,'Calls','class1Operation1,class2Operation1,class3Operation1'),
   (8,8,'Calls','None'),
   (9,9,'Calls','class2Operation1');
SELECT op1.Name
FROM t_object AS myClass 
LEFT JOIN t_operation AS op2 
    ON myClass.Object_ID = op2.Object_ID,
t_object AS obj1 
LEFT JOIN t_operation AS op1 
    ON obj1.Object_ID = op1.Object_ID 
INNER JOIN t_operationtag AS function_tag 
    ON ((op1.OperationID = function_tag.ElementID) 
    AND (function_tag.VALUE LIKE CONCAT("%", "class2Operation1", "%") 
    AND function_tag.Property = 'Calls'))
WHERE myClass.Object_ID = '1'
GROUP BY op1.Name


Name


class1Operation1

class3Operation1

class3Operation3