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31 lines
740 B
Text
31 lines
740 B
Text
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CREATE TABLE grandparent (
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id INT NOT NULL PRIMARY KEY
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) ENGINE=InnoDB;
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CREATE TABLE parent (
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id INT NOT NULL PRIMARY KEY,
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grandparent_id INT,
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FOREIGN KEY (grandparent_id)
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REFERENCES grandparent(id)
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ON DELETE CASCADE
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) ENGINE=InnoDB;
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CREATE TABLE child (
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id INT NOT NULL PRIMARY KEY,
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parent_id INT,
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FOREIGN KEY (parent_id)
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REFERENCES parent(id)
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ON DELETE CASCADE
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) ENGINE=InnoDB;
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INSERT INTO grandparent VALUES (1),(2);
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INSERT INTO parent VALUES (1,1), (2,2);
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INSERT INTO child VALUES (1,1), (2,2);
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DELETE FROM grandparent WHERE id = 1;
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SELECT COUNT(*) = 0 FROM parent WHERE grandparent_id = 1;
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COUNT(*) = 0
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1
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SELECT COUNT(*) = 0 FROM child WHERE parent_id = 1;
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COUNT(*) = 0
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1
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DROP TABLE child;
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DROP TABLE parent;
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DROP TABLE grandparent;
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