sql - 如何在单个 MySQL 语句中添加列并使其成为外键？

Question

在mysql中，我可以在同一个语句中添加列和外键吗？添加 fk 的正确语法是什么？

这是我的 SQL:

ALTER TABLE database.table
 ADD COLUMN columnname INT DEFAULT(1),
 FOREIGN KEY (fk_name) REFERENCES reftable(refcolumn) ON DELETE CASCADE;

...以及伴随的错误信息:

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'FOREIGN KEY (fk_name) REFERENCES reftable(refcolumn) ON DELETE CASCADE' at line 4

Answer 1

试试这个:

ALTER TABLE database.table
  ADD COLUMN columnname INT DEFAULT(1),
  ADD FOREIGN KEY fk_name(fk_column) REFERENCES reftable(refcolumn) ON DELETE CASCADE;