### 10.3.6 Character String Literal Character Set and Collation

 Every character string literal has a character set and a collation.

 For the simple statement `SELECT '*`string`*'`, the string has the connection default character set and collation defined by the [`character_set_connection`](server-system-variables.html#sysvar_character_set_connection) and [`collation_connection`](server-system-variables.html#sysvar_collation_connection) system variables.

 A character string literal may have an optional character set introducer and `COLLATE` clause, to designate it as a string that uses a particular character set and collation:

[]()[]()

```
[_charset_name]'string' [COLLATE collation_name]
```

 The `_*`charset_name`*` expression is formally called an *introducer*. It tells the parser, “the string that follows uses character set *`charset_name`*.” An introducer does not change the string to the introducer character set like [`CONVERT()`](cast-functions.html#function_convert) would do. It does not change the string value, although padding may occur. The introducer is just a signal. See [Section 10.3.8, “Character Set Introducers”](charset-introducer.html).

 Examples:

```
SELECT 'abc';
SELECT _latin1'abc';
SELECT _binary'abc';
SELECT _utf8mb4'abc' COLLATE utf8mb4_danish_ci;
```

 Character set introducers and the `COLLATE` clause are implemented according to standard SQL specifications.

 MySQL determines the character set and collation of a character string literal in the following manner:

* If both *`_charset_name`* and `COLLATE *`collation_name`*` are specified, character set *`charset_name`* and collation *`collation_name`* are used. *`collation_name`* must be a permitted collation for *`charset_name`*.

* If *`_charset_name`* is specified but `COLLATE` is not specified, character set *`charset_name`* and its default collation are used. To see the default collation for each character set, use the [`SHOW CHARACTER SET`](show-character-set.html) statement or query the `INFORMATION_SCHEMA` [`CHARACTER_SETS`](information-schema-character-sets-table.html) table.

* If *`_charset_name`* is not specified but `COLLATE *`collation_name`*` is specified, the connection default character set given by the [`character_set_connection`](server-system-variables.html#sysvar_character_set_connection) system variable and collation *`collation_name`* are used. *`collation_name`* must be a permitted collation for the connection default character set.

* Otherwise (neither *`_charset_name`* nor `COLLATE *`collation_name`*` is specified), the connection default character set and collation given by the [`character_set_connection`](server-system-variables.html#sysvar_character_set_connection) and [`collation_connection`](server-system-variables.html#sysvar_collation_connection) system variables are used.

 Examples:

* A nonbinary string with `latin1` character set and `latin1_german1_ci` collation:

  ```
  SELECT _latin1'Müller' COLLATE latin1_german1_ci;
  ```

* A nonbinary string with `utf8mb4` character set and its default collation (that is, `utf8mb4_0900_ai_ci`):

  ```
  SELECT _utf8mb4'Müller';
  ```

* A binary string with `binary` character set and its default collation (that is, `binary`):

  ```
  SELECT _binary'Müller';
  ```

* A nonbinary string with the connection default character set and `utf8mb4_0900_ai_ci` collation (fails if the connection character set is not `utf8mb4`):

  ```
  SELECT 'Müller' COLLATE utf8mb4_0900_ai_ci;
  ```

* A string with the connection default character set and collation:

  ```
  SELECT 'Müller';
  ```

 An introducer indicates the character set for the following string, but does not change how the parser performs escape processing within the string. Escapes are always interpreted by the parser according to the character set given by [`character_set_connection`](server-system-variables.html#sysvar_character_set_connection).

 The following examples show that escape processing occurs using [`character_set_connection`](server-system-variables.html#sysvar_character_set_connection) even in the presence of an introducer. The examples use [`SET NAMES`](set-names.html) (which changes [`character_set_connection`](server-system-variables.html#sysvar_character_set_connection), as discussed in [Section 10.4, “Connection Character Sets and Collations”](charset-connection.html)), and display the resulting strings using the [`HEX()`](string-functions.html#function_hex) function so that the exact string contents can be seen.

 Example 1:

```
mysql> SET NAMES latin1;
mysql> SELECT HEX('à\n'), HEX(_sjis'à\n');
+------------+-----------------+
| HEX('à\n')  | HEX(_sjis'à\n')  |
+------------+-----------------+
| E00A       | E00A            |
+------------+-----------------+
```

 Here, `à` (hexadecimal value `E0`) is followed by `\n`, the escape sequence for newline. The escape sequence is interpreted using the [`character_set_connection`](server-system-variables.html#sysvar_character_set_connection) value of `latin1` to produce a literal newline (hexadecimal value `0A`). This happens even for the second string. That is, the `_sjis` introducer does not affect the parser's escape processing.

 Example 2:

```
mysql> SET NAMES sjis;
mysql> SELECT HEX('à\n'), HEX(_latin1'à\n');
+------------+-------------------+
| HEX('à\n')  | HEX(_latin1'à\n')  |
+------------+-------------------+
| E05C6E     | E05C6E            |
+------------+-------------------+
```

 Here, [`character_set_connection`](server-system-variables.html#sysvar_character_set_connection) is `sjis`, a character set in which the sequence of `à` followed by `\` (hexadecimal values `05` and `5C`) is a valid multibyte character. Hence, the first two bytes of the string are interpreted as a single `sjis` character, and the `\` is not interpreted as an escape character. The following `n` (hexadecimal value `6E`) is not interpreted as part of an escape sequence. This is true even for the second string; the `_latin1` introducer does not affect escape processing.

