Name resolution of SQL objects

Informix®

Informix uses the following form to identify an SQL object:

database[@dbservername]:][{owner|"owner"}.]identifier

The ANSI convention is to use double quotes for identifier delimiters (For example: "customer"."cust_name").

Informix database object names are not case-sensitive in non-ANSI databases. When using double-quoted identifiers, Informix becomes case sensitive.

With non-ANSI Informix databases, you do not have to give a schema name before the tables when executing an SQL statement:

SELECT ... FROM customer WHERE ...

In Informix ANSI compliant databases:

The table name must include "owner", unless the connected user is the owner of the database object.
The database server shifts the owner name to uppercase letters before the statement executes, unless the owner name is enclosed in double quotes.

ORACLE

With Oracle®, an object name takes the following form:

[(schema|"schema").](identifier|"identifier")[@database-link]

Oracle has separate namespaces for different classes of objects (tables, views, triggers, indexes, clusters).

Object names are limited to 30 chars in ORACLE.

Unlike Informix, Oracle database object names are stored in UPPERCASE in system catalogs. That means that SELECT "col1" FROM "tab1" will produce an error because those objects are identified by "COL1" and "TAB1" in Oracle system catalogs.

An Oracle database schema is owned by a user (usually, the application administrator) and this user must create PUBLIC SYNONYMS to provide a global scope for his table names. PUBLIC SYNONYMS can have the same name as the schema objects they point to.

Solution

As a general rule, to write portable SQL, it is recommended that you only use simple database object names without any database, server or owner qualifier and without quoted identifiers.

Check that you do not use single-quoted or double-quoted table names or column names in your source. Those quotes must be removed because the database interface automatically converts double quotes to single quotes, and Oracle does not allow single quotes as database object name delimiters.