Treating a warning that doesn't make sense to me (from a basic join)

[EinarRoed]

Say I want to create a table called POLICY. It should be identical to the source table POLICY_SRC, except that it should only contain the policies that are represented in the source table POLICY_LOAD. The primary key in all tables is policy_id.

Example code:

proc sql;
	create table POLICY as
	select * from POLICY_SRC src
	inner join POLICY_LOAD load on (src.policy_id = load.policy_id);
quit;

This gives the following warning:

WARNING: Variable policy_id already exists on file WORK.POLICY.

I only select the policy_id column from POLICY_SRC. So why this error?

I guess the code also selects policy_id from POLICY_LOAD, because of the join.

How would you resolve this warning? Can I drop the superfluous column somehow, in this proc sql?

Edit:The reason why I'm doing a SELECT * is that the actual table contain around 150+ columns, so I'd prefer not to list them all if it can be avoided. I'd like to just simply select * columns from POLICY_INPUT.

[PaigeMiller · Accepted solution]

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@EinarRoed wrote:

Say I want to create a table called POLICY. It should be identical to the source table POLICY_SRC, except that it should only contain the policies that are represented in the source table POLICY_LOAD. The primary key in all tables is policy_id.

Example code:

proc sql;
	create table POLICY as
	select * from POLICY_SRC src
	inner join POLICY_LOAD load on (src.policy_id = load.policy_id);
quit;

This gives the following warning:

WARNING: Variable policy_id already exists on file WORK.POLICY.

I only select the policy_id column from POLICY_SRC. So why this error?

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This is not correct. You have selected all variables from POLICY_SRC. That's what the * indicates. There is a variable named POLICY_ID in both data sets.

In this case, I think it would be fine to ignore the warning, as the information it is providing is expected. (Sometimes warnings provide unexpected information, and then you should not ignore the warning)

[EinarRoed]

For some reason I thought that the SELECT would only select policy_id from the "FROM-table" and not from the "JOIN-table" unless specified. But yeah I see that it makes sense that it selects all columns from both tables. I'll just live with the warning then, thanks.