How do I use quoted identifier for user + table name combination in Oracle?

Question

In my Oracle DB setup all the tables are created under dedicated user account SYS0MYUSER. When executing following query on my system I got SQL Error: ORA-00903: invalid table name

SELECT COUNT(*) FROM SYS0MYUSER.USER;

I tried to escape the reserved keyword like this:

SELECT COUNT(*) FROM "SYS0MYUSER.USER";

But then I got another error SQL Error: ORA-00942: table or view does not exist

What is the correct way to escape user name + reserved keyword combination ?

UPDATE: What's about table alias do I have to use double quotes too ?

Answer 1

If you have created the table using quoted identifier, then you must always use double-quotation marks wherever you refer the object.

From documentation,

Database Object Naming Rules

Every database object has a name. In a SQL statement, you represent the name of an object with a quoted identifier or a nonquoted identifier.

• A quoted identifier begins and ends with double quotation marks ("). If you name a schema object using a quoted identifier, then you must use the double quotation marks whenever you refer to that object.

• A nonquoted identifier is not surrounded by any punctuation.

For example,

SQL> CREATE TABLE "USER"(A NUMBER);

Table created.

SQL>
SQL> SELECT COUNT(*) FROM LALIT.USER;
SELECT COUNT(*) FROM LALIT.USER
                           *
ERROR at line 1:
ORA-00903: invalid table name


SQL>
SQL> SELECT COUNT(*) FROM LALIT."USER";

  COUNT(*)
----------
         0

SQL>

So, you need to refer the table as a quoted identifier:

SELECT COUNT(*) FROM SYS0MYUSER."USER";

Update OP updated his question regarding table alias.

What's about table alias do I have to use double quotes too ?

Table alias has nothing to do with the quoted identifier.

For example,

SQL> SELECT t.* FROM LALIT."USER" t;

no rows selected

SQL>

Answer 2

SELECT COUNT(*) FROM "SYS0MYUSER"."USER";