Delete permission implementation differences

I mentioned when grant statements take into effect in Sql Server, MySql, and Oracle here.

I found out recently that there are some implementation differences when you grant only delete permission on a table to a user. MySql and Sql Server do this the same way, whereas Oracle is different.

Suppose you have:

1. Table t1: create table t1 (c1 int);
2. User TestLogin. The only permission of this TestLogin is delete on t1.

In all 3 database platforms, TestLogin can find out what columns t1 has by default, using either

desc t1


sp_columns t1

In both Sql Server and MySql, the only thing you can do is:

delete from t1;

which essentially wipes out the whole table. You can do the same thing in Oracle.

However, if you do:

delete from t1 where c1 = 1;

you will get a select permission denied in both Sql Server and MySql, but Oracle will allow you to do it.

Personally, I think Oracle’s implementation is wrong on this one, because this gives TestLogin select permissions on this table. For example, suppose the table is a salary table, TestLogin can find out columns using desc, then it can do something like:

delete from SalaryTable where FirstName = ‘John’ and LastName = ‘Doe’ and SalaryAmount >= 50000 and SalaryAmount <= 50050; If the statement returns “one row affected”, then the person would know John Doe’s salary. This person can then issue rollback If “no row affected” is returned, the person can continue until s/he can find it out. I did a quick search on ANSI SQL 92 standard, but didn’t find anything, so I am not sure which way is consistent with ANSI 92. My check was brief, though, so I may have overlooked it.

Leave a Reply

Your email address will not be published. Required fields are marked *