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Asked: 2026-05-28T20:51:55+00:00

I searched for a solution to this problem on the Internet and checked the

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I searched for a solution to this problem on the Internet and checked the Stack Overflow questions, but none of the solutions worked for my case.

I want to create a foreign key from table sira_no to metal_kod.

ALTER TABLE sira_no
    ADD CONSTRAINT METAL_KODU FOREIGN KEY(METAL_KODU)
    REFERENCES metal_kod(METAL_KODU)
    ON DELETE SET NULL
    ON UPDATE SET NULL ;

This script returns:

Error Code: 1005. Can't create table 'ebs.#sql-f48_1a3' (errno: 150)

I tried adding an index to the referenced table:

CREATE INDEX METAL_KODU_INDEX ON metal_kod (METAL_KODU);

I checked METAL_KODU on both tables (charset and collation), but I couldn’t find a solution to this problem. How can I fix this problem?

Here is the metal_kod table:

METAL_KODU    varchar(4)    NO    PRI
DURUM    bit(1)    NO
METAL_ISMI    varchar(30)    NO
AYAR_YOGUNLUK    smallint(6)    YES        100
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1 Answer

  1. Editorial Team

    Error Code: 1005 — there is a wrong primary key reference in your code

    Usually it’s due to a referenced foreign key field that does not exist. It might be you have a typo mistake, or check case it should be same, or there’s a field-type mismatch. Foreign key-linked fields must match definitions exactly.

    Some known causes may be:

    1. The two key fields type and/or size doesn’t match exactly. For example, if one is INT(10) the key field needs to be INT as well and not BIGINT or SMALLINT or TINYINT. You should also check that one is not SIGNED and the other is UNSIGNED. They both need to be exactly the same.
    2. One of the key field that you are trying to reference does not have an index and/or is not a primary key. If one of the fields in the relationship is not a primary key, you must create an index for that field.
    3. The foreign key name is a duplicate of an already existing key. Check that the name of your foreign key is unique within your database. Just add a few random characters to the end of your key name to test for this.
    4. One or both of your tables is a MyISAM table. In order to use foreign keys, the tables must both be InnoDB. (Actually, if both tables are MyISAM then you won’t get an error message – it just won’t create the key.) In Query Browser, you can specify the table type.
    5. You have specified a cascade ON DELETE SET NULL, but the relevant key field is set to NOT NULL. You can fix this by either changing your cascade or setting the field to allow NULL values.
    6. Make sure that the Charset and Collate options are the same both at the table level as well as individual field level for the key columns.
    7. You have a default value (that is, default=0) on your foreign key column
    8. One of the fields in the relationship is part of a combination (composite) key and does not have its own individual index. Even though the field has an index as part of the composite key, you must create a separate index for only that key field in order to use it in a constraint.
    9. You have a syntax error in your ALTER statement or you have mistyped one of the field names in the relationship
    10. The name of your foreign key exceeds the maximum length of 64 characters.

    For more details, refer to: MySQL Error Number 1005 Can’t create table

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