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+---
+title: Schema 对象名
+category: reference
+summary: 本文介绍 TiDB SQL 语句中的模式对象名。
+aliases: ['/docs-cn/dev/reference/sql/language-structure/schema-object-names/']
+---
+
+# Schema Object Names
+
+<!-- markdownlint-disable MD038 -->
+
+This article introduces schema object names in TiDB SQL statements.
+
+Schema object names are used to name all schema objects in TiDB, including database, table, index, column, alias, etc. You can quote these objects by identifiers in SQL statements.
+
+To quote, you can use the backtick ``(`)``  to wrap the identifier, ie `SELECT * FROM t` can also be written as`` SELECT * FROM `t` ``. But if an identifier contains at least a special character or is a reserved keyword, you must quote it whenever you refer to it. 
+
+{{< copyable "sql" >}}
+
+```sql
+SELECT * FROM `table` WHERE `table`.id = 20;
+```
+
+If the `ANSI_QUOTES` SQL mode is enabled, you can also quote identifiers within double quotation marks`"`.
+
+```sql
+MySQL [test]> CREATE TABLE "test" (a varchar(10));
+ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your TiDB version for the right syntax to use line 1 column 19 near ""test" (a varchar(10))" 
+
+MySQL [test]> SET SESSION sql_mode='ANSI_QUOTES';
+Query OK, 0 rows affected (0.000 sec)
+
+MySQL [test]> CREATE TABLE "test" (a varchar(10));
+Query OK, 0 rows affected (0.012 sec)
+```
+
+If you want to use the backtick character in the quoted identifier, you need to repeat the backtick twice, for example to create a table a`b:
+
+{{< copyable "sql" >}}
+
+```sql
+CREATE TABLE `a``b` (a int);
+```
+
+In a `SELECT` statement, the alias part can use an identifier or a string:
+
+{{< copyable "sql" >}}
+
+```sql
+SELECT 1 AS `identifier`, 2 AS 'string';
+```
+
+```
++------------+--------+
+| identifier | string |
++------------+--------+
+|          1 |      2 |
++------------+--------+
+1 row in set (0.00 sec)
+```
+
+For more information, see [MySQL Documentation](https://dev.mysql.com/doc/refman/5.7/en/identifiers.html).
+
+## Identifier Qualifiers
+
+Object names can be unqualified or qualified. For example, the following statement creates a table using the unqualified name:
+
+{{< copyable "sql" >}}
+
+```sql
+CREATE TABLE t (i int);
+```
+
+If you have not used the `USE` or connection parameter to set the database, the `ERROR 1046 (3D000): No database selected` is displayed. At this time you can specify the database qualified name:
+
+{{< copyable "sql" >}}
+
+```sql
+CREATE TABLE test.t (i int);
+```
+
+There can be white spaces around `.`, and `table_name.col_name` and `table_name . col_name` are equivalent.
+
+To quote this identifier, use:
+
+```
+`table_name`.`col_name`
+```
+
+Instead of:
+
+```
+`table_name.col_name`
+```
+
+For more information, see [MySQL Documentation](https://dev.mysql.com/doc/refman/5.7/en/identifier-qualifiers.html).