reference: update documents for new collation by TomShawn · Pull Request #2350 · pingcap/docs

TomShawn · 2020-04-20T14:04:59Z

What is changed, added or deleted? (Required)

Update documents for new collation.

Which TiDB version(s) do your changes apply to? (Required)

If you select two or more versions from above, to trigger the bot to cherry-pick this PR to your desired release version branch(es), you must add corresponding labels such as needs-cherry-pick-4.0, needs-cherry-pick-3.1, needs-cherry-pick-3.0, and needs-cherry-pick-2.1.

What is the related PR or file link(s)?

This PR is translated from: reference: add document for new collation docs-cn#2606 sql, toc: refine character set and collation document docs-cn#2884 sql: fix config name in collation doc docs-cn#2946 reference: refine expressions in characterset-and-collation.md docs-cn#3056
Other reference link(s):

wjhuang2016

LGTM

yikeke · 2020-05-12T05:37:51Z

Sorry, I'll review this PR later today.

yikeke · 2020-05-13T01:34:07Z

 ```

-The `alter_specification` option specifies the `CHARACTER SET` and `COLLATE` of a specified database. Currently, TiDB only supports some character sets and collations. See [Character Set Support](/reference/sql/character-set.md) for details.
+The `alter_specification` option specifies the `CHARACTER SET` and `COLLATE` of a specified database. Currently, TiDB only supports some character sets and collations. See [Character Set Support](/reference/sql/characterset-and-collation.md) for details.


Suggested change

The `alter_specification` option specifies the `CHARACTER SET` and `COLLATE` of a specified database. Currently, TiDB only supports some character sets and collations. See [Character Set Support](/reference/sql/characterset-and-collation.md) for details.

The `alter_specification` option specifies the `CHARACTER SET` and `COLLATE` of a specified database. Currently, TiDB only supports some character sets and collations. See [Character Set and Collation Support](/reference/sql/characterset-and-collation.md) for details.

yikeke · 2020-05-13T01:34:18Z

 If you create an existing database and does not specify `IF NOT EXISTS`, an error is displayed.

-The `create_specification` option is used to specify the specific `CHARACTER SET` and `COLLATE` in the database. Currently, TiDB only supports some of the character sets and collations. For details, see [Character Set Support](/reference/sql/character-set.md).
+The `create_specification` option is used to specify the specific `CHARACTER SET` and `COLLATE` in the database. Currently, TiDB only supports some of the character sets and collations. For details, see [Character Set and Collation Supports](/reference/sql/characterset-and-collation.md).


Suggested change

The `create_specification` option is used to specify the specific `CHARACTER SET` and `COLLATE` in the database. Currently, TiDB only supports some of the character sets and collations. For details, see [Character Set and Collation Supports](/reference/sql/characterset-and-collation.md).

The `create_specification` option is used to specify the specific `CHARACTER SET` and `COLLATE` in the database. Currently, TiDB only supports some of the character sets and collations. For details, see [Character Set and Collation Support](/reference/sql/characterset-and-collation.md).

yikeke · 2020-05-13T01:36:09Z

 * [SHOW \[GLOBAL|SESSION\] VARIABLES](/reference/sql/statements/show-variables.md)
 * [SET <variable>](/reference/sql/statements/set-variable.md)
-* [Character Set Support](/reference/sql/character-set.md)
+* [Character Set and Collation Supports](/reference/sql/characterset-and-collation.md)


Suggested change

* [Character Set and Collation Supports](/reference/sql/characterset-and-collation.md)

* [Character Set and Collation Support](/reference/sql/characterset-and-collation.md)

yikeke · 2020-05-13T01:37:04Z

 6. Check the Character Set.

-    TiDB differs from MySQL in [Character Set](/reference/sql/character-set.md).
+    TiDB differs from MySQL in [Character Set](/reference/sql/characterset-and-collation.md).


Suggested change

TiDB differs from MySQL in [Character Set](/reference/sql/characterset-and-collation.md).

TiDB differs from MySQL in [character sets](/reference/sql/characterset-and-collation.md).

yikeke · 2020-05-13T01:38:29Z

@@ -0,0 +1,374 @@
+---
+title: Character Set and Collation
+summary: Learn about the supported character sets in TiDB.


Suggested change

summary: Learn about the supported character sets in TiDB.

summary: Learn about the supported character sets and collations in TiDB.

yikeke · 2020-05-13T01:40:43Z

+>
+> Each character set might correspond to multiple collations, but by default each character set corresponds to only one collation.
+
+You can use the following statement to view the collation (under the [new framework for collations](#new-framework-for-collations)) that corresponds to the character set.


Suggested change

You can use the following statement to view the collation (under the [new framework for collations](#new-framework-for-collations)) that corresponds to the character set.

You can use the following statement to view the collations (under the [new framework for collations](#new-framework-for-collations)) that corresponds to the character set.

yikeke · 2020-05-13T01:45:26Z

+Query OK, 0 rows affected (0.08 sec)
+```
+
+The database character set and collation are used as the default values for table definitions if the table character set and collation are not specified in individual column definitions.


Suggested change

The database character set and collation are used as the default values for table definitions if the table character set and collation are not specified in individual column definitions.

If the table character set and collation are not specified, the database character set and collation are used as their default values.

yikeke · 2020-05-13T01:46:36Z

+
+## Column character set and collation
+
+See the following table for the character set and collation syntax for columns:


Suggested change

See the following table for the character set and collation syntax for columns:

You can use the following statement to specify the character set and collation for columns:

yikeke · 2020-05-13T01:47:36Z

+    [COLLATE collation_name]
+```
+
+The table character set and collation are used as the default values for column definitions if the column character set and collation are not specified in individual column definitions.


Suggested change

The table character set and collation are used as the default values for column definitions if the column character set and collation are not specified in individual column definitions.

If the column character set and collation are not specified, the table character set and collation are used as their default values.

yikeke · 2020-05-13T01:51:10Z

+
+## String character sets and collation
+
+Each character literal in a string has a character set and a collation. When you use a string, this option is available:


Suggested change

Each character literal in a string has a character set and a collation. When you use a string, this option is available:

Each string corresponds to a character set and a collation. When you use a string, this option is available:

yikeke · 2020-05-13T01:51:11Z

+
+## String character sets and collation
+
+Each character literal in a string has a character set and a collation. When you use a string, this option is available:


Suggested change

Each character literal in a string has a character set and a collation. When you use a string, this option is available:

Each string corresponds to a character set and a collation. When you use a string, this option is available:

yikeke · 2020-05-13T01:52:37Z

+
+Rules:
+
+ Rule 1: If you specify `CHARACTER SET charset_name` and `COLLATE collation_name`, then `CHARACTER SET charset_name` and `COLLATE collation_name` are used directly.


Suggested change

+ Rule 1: If you specify `CHARACTER SET charset_name` and `COLLATE collation_name`, then `CHARACTER SET charset_name` and `COLLATE collation_name` are used directly.

+ Rule 1: If you specify `CHARACTER SET charset_name` and `COLLATE collation_name`, then `charset_name` and `collation_name` are used directly.

I changed the zh doc in pingcap/docs-cn#3056

yikeke · 2020-05-13T01:56:22Z

+Rules:
+
+ Rule 1: If you specify `CHARACTER SET charset_name` and `COLLATE collation_name`, then `CHARACTER SET charset_name` and `COLLATE collation_name` are used directly.
+ Rule 2: If you specify `CHARACTER SET charset_name` but do not specify `COLLATE collation_name`, `CHARACTER SET charset_name` and the default collation of `CHARACTER SET charset_name` are used.


Suggested change

+ Rule 2: If you specify `CHARACTER SET charset_name` but do not specify `COLLATE collation_name`, `CHARACTER SET charset_name` and the default collation of `CHARACTER SET charset_name` are used.

+ Rule 2: If you specify `CHARACTER SET charset_name` but do not specify `COLLATE collation_name`, `charset_name` and the default collation of `charset_name` are used.

yikeke · 2020-05-13T01:56:45Z

+
+## General rules on selecting character sets and collation
+
+ Rule 1: If you specify `CHARACTER SET charset_name` and `COLLATE collation_name`, then `CHARACTER SET charset_name` and `COLLATE collation_name` are used directly.


Suggested change

+ Rule 1: If you specify `CHARACTER SET charset_name` and `COLLATE collation_name`, then `CHARACTER SET charset_name` and `COLLATE collation_name` are used directly.

+ Rule 1: If you specify `CHARACTER SET charset_name` and `COLLATE collation_name`, then `charset_name` and `collation_name` are used directly.

yikeke · 2020-05-13T01:57:01Z

+## General rules on selecting character sets and collation
+
+ Rule 1: If you specify `CHARACTER SET charset_name` and `COLLATE collation_name`, then `CHARACTER SET charset_name` and `COLLATE collation_name` are used directly.
+ Rule 2: If you specify `CHARACTER SET charset_name` and do not specify `COLLATE collation_name`, then `CHARACTER SET charset_name` and the default comparison collation of `CHARACTER SET charset_name` are used.


Suggested change

+ Rule 2: If you specify `CHARACTER SET charset_name` and do not specify `COLLATE collation_name`, then `CHARACTER SET charset_name` and the default comparison collation of `CHARACTER SET charset_name` are used.

+ Rule 2: If you specify `CHARACTER SET charset_name` and do not specify `COLLATE collation_name`, then `charset_name` and the default collation of `charset_name` are used.

yikeke · 2020-05-13T02:32:21Z

+ Rule 2: If you specify `CHARACTER SET charset_name` but do not specify `COLLATE collation_name`, `CHARACTER SET charset_name` and the default collation of `CHARACTER SET charset_name` are used.
+ Rule 3: If you specify neither `CHARACTER SET charset_name` nor `COLLATE collation_name`, the character set and collation given by the system variables `character_set_connection` and `collation_connection` are used.
+
+## Connection character sets and collations


Suggested change

## Connection character sets and collations

## Client connection character set and collation

yikeke · 2020-05-13T02:35:33Z

+
+ The server character set and collation are the values of the `character_set_server` and `collation_server` system variables.
+
+ The character set and collation of the default database are the values of the `character_set_database` and `collation_database` system variables. You can use `character_set_connection` and `collation_connection` to specify the character set and collation for each connection. The `character_set_client` variable is to set the client character set. Before returning the result, the `character_set_results` system variable indicates the character set in which the server returns query results to the client, including the metadata of the result.


Suggested change

+ The character set and collation of the default database are the values of the `character_set_database` and `collation_database` system variables. You can use `character_set_connection` and `collation_connection` to specify the character set and collation for each connection. The `character_set_client` variable is to set the client character set. Before returning the result, the `character_set_results` system variable indicates the character set in which the server returns query results to the client, including the metadata of the result.

+ The character set and collation of the default database are the values of the `character_set_database` and `collation_database` environment variables.

You can use `character_set_connection` and `collation_connection` to specify the character set and collation for each client connection.

The `character_set_client` variable is to set the client character set. Before returning the result, the server converts the query result to the character set corresponding to the `character_set_results` variable, including the metadata of the result.

yikeke · 2020-05-13T02:40:08Z

+
+ The character set and collation of the default database are the values of the `character_set_database` and `collation_database` system variables. You can use `character_set_connection` and `collation_connection` to specify the character set and collation for each connection. The `character_set_client` variable is to set the client character set. Before returning the result, the `character_set_results` system variable indicates the character set in which the server returns query results to the client, including the metadata of the result.
+
+You can use the following statement to specify a particular collation that is related to the client:


Suggested change

You can use the following statement to specify a particular collation that is related to the client:

You can use the following statement to set the character set and collation that is related to the client:

yikeke · 2020-05-13T03:54:19Z

+
+## Validity check of characters
+
+For the specified `utf8` or `utf8mb4` character set, TiDB only supports the valid `utf8` character, and reports the `incorrect utf8 value` error when the character is invalid. This validity check of characters in TiDB is compatible with MySQL 8.0 but incompatible with MySQL 5.7 or earlier versions.


Suggested change

For the specified `utf8` or `utf8mb4` character set, TiDB only supports the valid `utf8` character, and reports the `incorrect utf8 value` error when the character is invalid. This validity check of characters in TiDB is compatible with MySQL 8.0 but incompatible with MySQL 5.7 or earlier versions.

If the specified character set is `utf8` or `utf8mb4`, TiDB only supports the valid `utf8` characters. For invalid characters, TiDB reports the `incorrect utf8 value` error. This validity check of characters in TiDB is compatible with MySQL 8.0 but incompatible with MySQL 5.7 or earlier versions.

yikeke · 2020-05-13T03:55:16Z

+For more information, see [Connection Character Sets and Collations in MySQL](https://dev.mysql.com/doc/refman/5.7/en/charset-connection.html).
+


Suggested change

For more information, see [Connection Character Sets and Collations in MySQL](https://dev.mysql.com/doc/refman/5.7/en/charset-connection.html).

yikeke · 2020-05-13T04:01:42Z

+
+The syntax support and semantic support for the collation are influenced by the [`new_collations_enabled_on_first_bootstrap`](/reference/configuration/tidb-server/configuration-file.md#new_collations_enabled_on_first_bootstrap) configuration item. The syntax support and semantic support are different. The former indicates that TiDB can parse and set collations. The latter indicates that TiDB can correctly use collations when comparing strings.
+
+Before v4.0, TiDB only supports syntactically parsing most of the MySQL collations but semantically takes all collations as binary collations, which is the [old framework for collations](#old-framework-for-collations).


Suggested change

Before v4.0, TiDB only supports syntactically parsing most of the MySQL collations but semantically takes all collations as binary collations, which is the [old framework for collations](#old-framework-for-collations).

Before v4.0, TiDB provides only the [old framework for collations](#old-framework-for-collations). In this framework, TiDB supports syntactically parsing most of the MySQL collations but semantically takes all collations as binary collations.

yikeke · 2020-05-13T04:02:38Z

+
+Before v4.0, TiDB only supports syntactically parsing most of the MySQL collations but semantically takes all collations as binary collations, which is the [old framework for collations](#old-framework-for-collations).
+
+Since v4.0, TiDB supports semantically parsing different collations and strictly following the collations when comparing strings, which is the [new framework for collations](#new-framework-for-collations).


Suggested change

Since v4.0, TiDB supports semantically parsing different collations and strictly following the collations when comparing strings, which is the [new framework for collations](#new-framework-for-collations).

Since v4.0, TiDB supports a [new framework for collations](#new-framework-for-collations). In this framework, TiDB semantically parses different collations and strictly follows the collations when comparing strings.

TomShawn · 2020-05-13T07:10:59Z

@yikeke All comments are addressed, PTAL again, thanks!

yikeke

To align new commits in pingcap/docs-cn#3056

Co-authored-by: Keke Yi <40977455+yikeke@users.noreply.github.com>

yikeke · 2020-05-13T08:39:33Z

/merge

sre-bot · 2020-05-13T08:42:06Z

/run-all-tests

sre-bot · 2020-05-13T08:44:56Z

cherry pick to release-4.0 in PR #2541

* reference: update documents for new collation (#2350) * Update reference/sql/characterset-and-collation.md Co-authored-by: TomShawn <41534398+TomShawn@users.noreply.github.com>

reference: update documents for new collation

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correct parameter name from pingcap#2802

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	The `alter_specification` option specifies the `CHARACTER SET` and `COLLATE` of a specified database. Currently, TiDB only supports some character sets and collations. See [Character Set Support](/reference/sql/characterset-and-collation.md) for details.
	The `alter_specification` option specifies the `CHARACTER SET` and `COLLATE` of a specified database. Currently, TiDB only supports some character sets and collations. See [Character Set and Collation Support](/reference/sql/characterset-and-collation.md) for details.

	The `create_specification` option is used to specify the specific `CHARACTER SET` and `COLLATE` in the database. Currently, TiDB only supports some of the character sets and collations. For details, see [Character Set and Collation Supports](/reference/sql/characterset-and-collation.md).
	The `create_specification` option is used to specify the specific `CHARACTER SET` and `COLLATE` in the database. Currently, TiDB only supports some of the character sets and collations. For details, see [Character Set and Collation Support](/reference/sql/characterset-and-collation.md).

	* [Character Set and Collation Supports](/reference/sql/characterset-and-collation.md)
	* [Character Set and Collation Support](/reference/sql/characterset-and-collation.md)

	TiDB differs from MySQL in [Character Set](/reference/sql/characterset-and-collation.md).
	TiDB differs from MySQL in [character sets](/reference/sql/characterset-and-collation.md).

	summary: Learn about the supported character sets in TiDB.
	summary: Learn about the supported character sets and collations in TiDB.

	You can use the following statement to view the collation (under the [new framework for collations](#new-framework-for-collations)) that corresponds to the character set.
	You can use the following statement to view the collations (under the [new framework for collations](#new-framework-for-collations)) that corresponds to the character set.

	The database character set and collation are used as the default values for table definitions if the table character set and collation are not specified in individual column definitions.
	If the table character set and collation are not specified, the database character set and collation are used as their default values.


		## Column character set and collation

		See the following table for the character set and collation syntax for columns:

	See the following table for the character set and collation syntax for columns:
	You can use the following statement to specify the character set and collation for columns:

	The table character set and collation are used as the default values for column definitions if the column character set and collation are not specified in individual column definitions.
	If the column character set and collation are not specified, the table character set and collation are used as their default values.


		## String character sets and collation

		Each character literal in a string has a character set and a collation. When you use a string, this option is available:

	Each character literal in a string has a character set and a collation. When you use a string, this option is available:
	Each string corresponds to a character set and a collation. When you use a string, this option is available:


		Rules:

		+ Rule 1: If you specify `CHARACTER SET charset_name` and `COLLATE collation_name`, then `CHARACTER SET charset_name` and `COLLATE collation_name` are used directly.

	+ Rule 2: If you specify `CHARACTER SET charset_name` but do not specify `COLLATE collation_name`, `CHARACTER SET charset_name` and the default collation of `CHARACTER SET charset_name` are used.
	+ Rule 2: If you specify `CHARACTER SET charset_name` but do not specify `COLLATE collation_name`, `charset_name` and the default collation of `charset_name` are used.


		## General rules on selecting character sets and collation

		+ Rule 1: If you specify `CHARACTER SET charset_name` and `COLLATE collation_name`, then `CHARACTER SET charset_name` and `COLLATE collation_name` are used directly.

	## Connection character sets and collations
	## Client connection character set and collation


		+ The server character set and collation are the values of the `character_set_server` and `collation_server` system variables.

		+ The character set and collation of the default database are the values of the `character_set_database` and `collation_database` system variables. You can use `character_set_connection` and `collation_connection` to specify the character set and collation for each connection. The `character_set_client` variable is to set the client character set. Before returning the result, the `character_set_results` system variable indicates the character set in which the server returns query results to the client, including the metadata of the result.

-+ The character set and collation of the default database are the values of the `character_set_database` and `collation_database` system variables. You can use `character_set_connection` and `collation_connection` to specify the character set and collation for each connection. The `character_set_client` variable is to set the client character set. Before returning the result, the `character_set_results` system variable indicates the character set in which the server returns query results to the client, including the metadata of the result.
++ The character set and collation of the default database are the values of the `character_set_database` and `collation_database` environment variables.
+You can use `character_set_connection` and `collation_connection` to specify the character set and collation for each client connection.
+The `character_set_client` variable is to set the client character set. Before returning the result, the server converts the query result to the character set corresponding to the `character_set_results` variable, including the metadata of the result.


		## Validity check of characters

		For the specified `utf8` or `utf8mb4` character set, TiDB only supports the valid `utf8` character, and reports the `incorrect utf8 value` error when the character is invalid. This validity check of characters in TiDB is compatible with MySQL 8.0 but incompatible with MySQL 5.7 or earlier versions.

	For the specified `utf8` or `utf8mb4` character set, TiDB only supports the valid `utf8` character, and reports the `incorrect utf8 value` error when the character is invalid. This validity check of characters in TiDB is compatible with MySQL 8.0 but incompatible with MySQL 5.7 or earlier versions.
	If the specified character set is `utf8` or `utf8mb4`, TiDB only supports the valid `utf8` characters. For invalid characters, TiDB reports the `incorrect utf8 value` error. This validity check of characters in TiDB is compatible with MySQL 8.0 but incompatible with MySQL 5.7 or earlier versions.

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TomShawn commented Apr 20, 2020 •

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		For more information, see [Connection Character Sets and Collations in MySQL](https://dev.mysql.com/doc/refman/5.7/en/charset-connection.html).


		The syntax support and semantic support for the collation are influenced by the [`new_collations_enabled_on_first_bootstrap`](/reference/configuration/tidb-server/configuration-file.md#new_collations_enabled_on_first_bootstrap) configuration item. The syntax support and semantic support are different. The former indicates that TiDB can parse and set collations. The latter indicates that TiDB can correctly use collations when comparing strings.

		Before v4.0, TiDB only supports syntactically parsing most of the MySQL collations but semantically takes all collations as binary collations, which is the [old framework for collations](#old-framework-for-collations).

	Before v4.0, TiDB only supports syntactically parsing most of the MySQL collations but semantically takes all collations as binary collations, which is the [old framework for collations](#old-framework-for-collations).
	Before v4.0, TiDB provides only the [old framework for collations](#old-framework-for-collations). In this framework, TiDB supports syntactically parsing most of the MySQL collations but semantically takes all collations as binary collations.


		Before v4.0, TiDB only supports syntactically parsing most of the MySQL collations but semantically takes all collations as binary collations, which is the [old framework for collations](#old-framework-for-collations).

		Since v4.0, TiDB supports semantically parsing different collations and strictly following the collations when comparing strings, which is the [new framework for collations](#new-framework-for-collations).

	Since v4.0, TiDB supports semantically parsing different collations and strictly following the collations when comparing strings, which is the [new framework for collations](#new-framework-for-collations).
	Since v4.0, TiDB supports a [new framework for collations](#new-framework-for-collations). In this framework, TiDB semantically parses different collations and strictly follows the collations when comparing strings.