mysql set to null code example

Example 1: mysql where value is null

SELECT *
FROM contacts
WHERE last_name IS NULL;

Example 2: set column to not null mysql

ALTER TABLE Person MODIFY P_Id INT(11) NOT NULL;

Example 3: mysql set value as null

UPDATE table SET field = NULL WHERE something = something

Example 4: mysql on delete set null

FOREIGN KEY (child_col1, child_col2, ... child_col_n)
    REFERENCES parent_table (parent_col1, parent_col2, ... parent_col_n)
    ON DELETE SET NULL
    [ ON UPDATE { NO ACTION | CASCADE | SET NULL | SET DEFAULT } ]

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Php Example

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