php - MySql 更新并将 null 设置为具有其他表外键的字段

Question

我有这样的表格:

Notes
ID | NAME | CATEGORY
1  | test | 1
2  | test2| 2

Notes Category
ID | NAME | COUNT
1  | tCat | 1
2  | tCat2| 1

我有外键 CATEGORY <-> Notes Category.ID

我尝试更新 Notes 中的第一条记录并将 null 设置为 CATEGORY，因为我想要没有类别的注释，但出现错误:

SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails

Answer 1

ALTER TABLE `Notes` DROP FOREIGN KEY Notes_ibfk_1;
UPDATE `Notes` SET CATEGORY = NULL WHERE ID = 1;
ALTER TABLE `Notes` ADD FOREIGN KEY -- http://dev.mysql.com/doc/refman/5.7/en/create-table-foreign-keys.html