Oracle Error ORA-00955

Error code

ORA-00955

Product

Oracle Database

Versions

Oracle Database 19c, 21c, 23ai and 26ai (same wording; IF NOT EXISTS from 23ai)

Category

Objects, Names & Identifiers

Last reviewed

24 October 2026

What it means

ORA-00955 means a CREATE statement tried to create a table, view, sequence, synonym, index or other object with a name that an object in the same schema and namespace already has.

Within a schema, each object needs a name that is unique in its namespace. Oracle's SQL Language Reference lists which objects share one namespace: tables, views, sequences, private synonyms, stand-alone procedures and functions, packages, user-defined types and operators. So a sequence cannot be called ORDERS if a table ORDERS exists. Indexes, constraints, triggers, clusters, dimensions, materialized views and private database links each have their own namespace, so a table and an index may share a name, but two indexes may not.

The message does not say which object holds the name or what type it is, so look it up in USER_OBJECTS. The usual reason is simply a script run twice. Oracle Database 23ai and later accept CREATE ... IF NOT EXISTS, which skips the statement when the object is already there; on 19c a script has to check first or handle the error.

Common causes

• A deployment or setup script is run a second time and creates objects that already exist.
• An object of a different type already has the name, for example a view, synonym or sequence called ORDERS when you create a table ORDERS.
• CREATE INDEX uses a name that another index in the schema already has.
• A previous failed or partial deployment left some objects behind.
• A materialized view is created with the name of an existing table (Oracle creates an internal table of the same name for it).

Diagnose it

Read-only These queries only read the data dictionary (USER_, ALL_ and DBA_ views) and dynamic performance views (V$). They do not change data, privileges or settings, so they are safe to run first. DBA_ and V$ views need the matching privileges.

SELECT object_name, object_type, status, created, last_ddl_time
FROM user_objects
WHERE object_name = 'ORDERS'
ORDER BY object_type;

SELECT index_name, table_name, uniqueness
FROM user_indexes
WHERE index_name = 'ORDERS_CUSTOMER_IX';

SELECT column_name, data_type, data_length, nullable
FROM user_tab_columns
WHERE table_name = 'ORDERS'
ORDER BY column_id;

How to fix it

Each fix is labelled with what it changes. Try read-only checks and the least invasive fix first, and test changes outside production.

CREATE TABLE IF NOT EXISTS shop.orders (
    id          NUMBER PRIMARY KEY,
    customer_id NUMBER,
    order_date  DATE
);

DECLARE
    name_in_use EXCEPTION;
    PRAGMA EXCEPTION_INIT(name_in_use, -955);
BEGIN
    EXECUTE IMMEDIATE 'CREATE SEQUENCE shop.orders_seq';
EXCEPTION
    WHEN name_in_use THEN NULL;  -- already there
END;
/

CREATE OR REPLACE VIEW shop.open_orders AS
SELECT id, customer_id, order_date
FROM shop.orders
WHERE status = 'OPEN';

DROP TABLE shop.orders_tmp;

CREATE TABLE shop.orders_tmp (id NUMBER PRIMARY KEY);

Examples

Running a setup script twice

Not reproduced here: no Oracle Database is installed for this site. The message text comes from Oracle's error reference and is the same in 19c and current releases. On 23ai and later, CREATE TABLE IF NOT EXISTS avoids it.

CREATE TABLE orders (
    id          NUMBER PRIMARY KEY,
    customer_id NUMBER
);

-- the same script, run again later
CREATE TABLE orders (
    id          NUMBER PRIMARY KEY,
    customer_id NUMBER
);

ORA-00955: name is already used by an existing object

A sequence with the same name as a table

Not reproduced here: no Oracle Database is installed for this site. Oracle's SQL Language Reference states that tables and sequences share a namespace, so a table and a sequence in the same schema cannot have the same name; the message format comes from its error reference. Names such as ORDERS_SEQ avoid the clash.

CREATE TABLE orders (id NUMBER PRIMARY KEY);

-- tables and sequences share one namespace
CREATE SEQUENCE orders;

ORA-00955: name is already used by an existing object

How to prevent it

Write deployment scripts so they can run twice: IF NOT EXISTS on 23ai and later, an existence check or a targeted exception handler on 19c, and CREATE OR REPLACE for views and PL/SQL. Use migration tooling that records which scripts have run.

Adopt a naming convention that separates object types, for example ORDERS for the table, ORDERS_SEQ for its sequence, ORDERS_V for a view and ORDERS_CUSTOMER_IX for an index, so names never collide across the shared namespace.

Common questions

Learn more on CodeWithSQL

• DDL commands
• SQL commands: DDL, DML, DCL, TCL and DQL

Official documentation

• ORA-00955 (Oracle Database Error Messages)
• Database object names and qualifiers: namespaces (Oracle SQL Language Reference 19c)
• CREATE TABLE: IF NOT EXISTS (Oracle SQL Language Reference 26ai)
• USER_OBJECTS (Oracle Database Reference 19c)

Last technically reviewed 24 October 2026; examples and diagnostics run on Oracle Database Error Messages reference (26ai, 21c and 19c); not run locally. Messages and explanations follow Oracle's Database Error Messages reference; no Oracle Database was available, so the examples were not run locally.