> For the complete documentation index, see [llms.txt](https://mariadb.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mariadb.com/docs/server/reference/error-codes/mariadb-error-codes-1000-to-1099/e1066.md).

# Error 1066: Not unique table/alias

| Error Code | SQLSTATE | Error              | Description                  |
| ---------- | -------- | ------------------ | ---------------------------- |
| 1066       | 42000    | ER\_NONUNIQ\_TABLE | Not unique table/alias: '%s' |

## Possible Causes and Solutions

In order to avoid ambiguity, a table name or alias must uniquely identify an object. There are many situations where this could occur.

For example, [HANDLER](https://github.com/mariadb-corporation/docs-server/blob/test/general-resources/community/sql-structure/nosql/handler/handler-commands.md) statements use unqualified table names, requiring the use of an alias in certain contexts. For example:

```
CREATE TABLE t1 (f1 INT);

INSERT INTO t1 VALUES (1),(2),(3);

HANDLER t1 OPEN;

HANDLER t1 READ NEXT;
+------+
| f1   |
+------+
|    1 |
+------+

HANDLER t1 READ NEXT;
+------+
| f1   |
+------+
|    2 |
+------+
```

In the previous example, the HANDLER was opened with the t1 table name. Since HANDLERs use unqualified table names, trying to access another table with this same name, even though it's in another database, will result in ambiguity. An alias needs to be used to avoid the ambiguity:

```
CREATE DATABASE db_new;

CREATE TABLE db_new.t1 (id INT);

INSERT INTO db_new.t1 VALUES (4),(5),(6);

HANDLER db_new.t1 OPEN;
ERROR 1066 (42000): Not unique table/alias: 't1'

HANDLER db_new.t1 OPEN AS db_new_t1;

HANDLER db_new_t1 READ NEXT LIMIT 3;
+------+
| id   |
+------+
|    4 |
|    5 |
|    6 |
+------+
```

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