Why can't Navicat set foreign keys and save them?

The reasons for unsuccessful saving of foreign keys set in Navicat may be: table structure mismatch (foreign key column and reference column types/lengths are inconsistent) circular reference (foreign key forms a circular reference, such as A table foreign key reference) B table, and B table foreign keys refer to A table) constraint conflicts (foreign key settings will cause data integrity constraint conflicts) other restrictions (number of foreign keys, limit on the number of reference columns)

Solution to the failure to save the foreign key when setting it in Navicat

The failure to save the foreign key when setting the foreign key in Navicat may be due to the following reasons:

1. Table structure mismatch

Foreign key columns and reference columns must have the same data type and length. If the two do not match, Navicat will not be able to save the foreign key settings.

2. Circular reference

Foreign key references cannot form circular references. For example, a foreign key in table A refers to table B, and a foreign key in table B refers to table A. This will cause Navicat to be unable to save foreign key settings.

3. Constraint Violation

If foreign key settings would cause a data integrity constraint violation, Navicat will not be able to save the settings. For example, if there is a record in table A that references a record that does not exist in table B, Navicat cannot save the foreign key settings.

4. Other restrictions

Navicat also has some restrictions when setting foreign keys, including:

• Each foreign key can only Can reference 10 columns.
• Each table can only have a maximum of 9 foreign key constraints.

Solution:

1. Check the table structure: Ensure that the data type and length of the foreign key column and the reference column are consistent .
2. Eliminate circular references: Redesign the table structure to avoid circular references.
3. Resolving data integrity issues: Ensure that all records exist in the relevant tables.
4. obey restrictions: Limit the number of foreign keys and the number of referenced columns.
5. Re-establish foreign keys: After eliminating the above problems, right-click the target table and select "Foreign Keys" > "New Foreign Key" to reset the foreign keys.

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