SQL如何在插入前检查列是否存在

Question

I need to migrate company emails into user emails

INSERT INTO public.user_emails ( SELECT DISTINCT
    ar. "userId",
    c. "companyEmail"
FROM
    public.companies AS c
    INNER JOIN public.account_roles AS ar ON c.id = ar. "companyId"
        AND ar. "employeeId" IS NULL
WHERE
    ar. "userId" NOT IN (
        SELECT
            "userId"
        FROM
            public.user_emails));

At the moment I get this error:

[ERROR] AssertionError [ERR_ASSERTION]: ifError got unwanted exception: column c.companyEmail does not exist

How can I add IF EXISTS or CASE logic here to check if c.companyEmail exists?

Answer 1

It seems postgresql does have this statement.

ALTER TABLE companies 
  ADD companyEmail IF NOT EXISTS companyEmail varchar(32);

Then after this you can run the insert sql.

But again, this is not recommended. DDL and DML should be run with different roles, the role to insert should not have permission to change table structure.

Answer 2

which kind of database? if mysql, you can try INSERT INTO .. ON DUPLICATE KEY