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[英]MySQL: How to update foreign key field, and create a relationship, after table values have been set with default values?
[英]MySql Update and Set null to field with foreign key to other table
我有這樣的表:
Notes
ID | NAME | CATEGORY
1 | test | 1
2 | test2| 2
Notes Category
ID | NAME | COUNT
1 | tCat | 1
2 | tCat2| 1
而且我有外鍵CATEGORY <-> Notes Category.ID
我嘗試在Notes中更新第一條記錄,並將null設置為CATEGORY,因為我想要沒有類別的筆記,我得到錯誤:
SQLSTATE [23000]:完整性約束違規:1452無法添加或更新子行:外鍵約束失敗
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
嘗試在NOTES表中特別聲明CATEGORY為INT NULL
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