I'm trying to create a foreign key. The columns in both tables are VARCHAR(45) and neither is a PK, however I keep getting this error message:

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It is saying the PK of reference table is INT, which is true, but I am not referencing this column, I am referencing another column in this table that is VARCHAR(45).

I have already made to FK in this same table where both columns are VARCHAR(45), which is why I am wondering what I am doing wrong this time.


Just figured it out.

The reference table column needed to be a Unique Index, then the foreign key worked.

Not a DB guy, but that sounds like a rookie mistake on my part.

  • can u share the schema or table structure or fields of table?
    – Karthick
    Commented Jul 31, 2014 at 10:31
  • @user44730: Right, a FK should always reference either a PRIMARY or a UNIQUE key (i.e. a column or columns with a PRIMARY KEY constraint or a UNIQUE constraint). Commented Jul 31, 2014 at 10:51
  • 1
    Why don't you put the answer into an answer rather than an edit to the question? Answering your own questions is allowed, encouraged even. Commented Jul 31, 2014 at 11:58

1 Answer 1


From the error message, what i can deduce is that a foreign key is trying to reference a table with a primary key of int, while it also has a primary key of int set on it's table, a bit confusing.

But try removing the primary key on the referencing table like table two below, it should work fine. so you could do something like

TABLE 1 TABLE 2 Id(int)(pk) id(int) name(varchar) ------ frontname(varchar)(fk)


TABLE 1 TABLE 2 Id(int)(pk) id(int)(pk) name(varchar)(pk2) ------ frontname(varchar)(pk2)(fk)

Not sure of the second one though

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