#Python

I have table

CREATE TABLE nodes (
        name VARCHAR(50) NOT NULL, 
        parent VARCHAR(50), 
        PRIMARY KEY (name), 
        FOREIGN KEY(parent) REFERENCES nodes (name) ON UPDATE cascade
);

I put some data

INSERT INTO nodes (name, parent) VALUES ('n1', NULL);
INSERT INTO nodes (name, parent) VALUES ('n11', 'n1');
INSERT INTO nodes (name, parent) VALUES ('n12', 'n1');
INSERT INTO nodes (name, parent) VALUES ('n13', 'n1');

Let's delete all

DELETE FROM nodes;

Nope, no way.

SQL Error [124] [S1000]: [SQLCODE: <-124>:<FOREIGN KEY constraint failed referential check upon DELETE of row in referenced table>]
[Location: <ServerLoop>]
[%msg: <At least 1 Row exists in table 'SQLUser.nodes' which references key 'NODESPKey2' - Foreign Key Constraint 'NODESFKey3', Field(s) 'parent' failed on referential action of NO ACTION>]