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Editorial Team
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Asked: 2026-05-14T22:22:00+00:00

I have a column with the type of Varchar in my Postgres database which

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I have a column with the type of Varchar in my Postgres database which I meant to be integers… and now I want to change them, unfortunately this doesn’t seem to work using my rails migration.

change_column :table1, :columnB, :integer

Which seems to output this SQL:

ALTER TABLE table1 ALTER COLUMN columnB TYPE integer

So I tried doing this:

execute 'ALTER TABLE table1 ALTER COLUMN columnB TYPE integer USING CAST(columnB AS INTEGER)'

but cast doesn’t work in this instance because some of the column are null…

any ideas?

Error:

PGError: ERROR:  invalid input syntax for integer: ""
: ALTER TABLE table1 ALTER COLUMN columnB TYPE integer USING CAST(columnB AS INTEGER)

Postgres v8.3

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1 Answer

  1. Editorial Team

    It sounds like the problem is that you have empty strings in your table. You’ll need to handle those, probably with a case statement, such as:

    execute %{ALTER TABLE "table1" ALTER COLUMN columnB TYPE integer USING CAST(CASE columnB WHEN '' THEN NULL ELSE columnB END AS INTEGER)}

    Update: completely rewritten based on updated question.

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