sql not null
SELECT column_name FROM table_name
WHERE column_name IS NOT NULL;sql not null
SELECT column_name FROM table_name
WHERE column_name IS NOT NULL;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 } ]Copyright © 2021 Codeinu
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