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ebnf show collation #17018

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Apr 8, 2024
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ebnf show collation #17018

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ebnf show collation
dveeden Apr 8, 2024
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Update sql-statements/sql-statement-show-collation.md
hfxsd Apr 8, 2024
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Update sql-statements/sql-statement-show-collation.md
hfxsd Apr 8, 2024
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Update sql-statements/sql-statement-show-collation.md
dveeden Apr 8, 2024
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38 changes: 34 additions & 4 deletions sql-statements/sql-statement-show-collation.md
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Expand Up @@ -14,16 +14,24 @@ This statement provides a static list of collations, and is included to provide

## Synopsis

**ShowCollationStmt:**
```ebnf+diagram
ShowCollationStmt ::=
"SHOW" "COLLATION" ShowLikeOrWhere?

![ShowCollationStmt](/media/sqlgram/ShowCollationStmt.png)
ShowLikeOrWhere ::=
"LIKE" SimpleExpr
| "WHERE" Expression
```

## Examples

When new collation framework is disabled, only binary collations are displayed.

```sql
mysql> SHOW COLLATION;
SHOW COLLATION;
```

```
+-------------+---------+------+---------+----------+---------+
| Collation | Charset | Id | Default | Compiled | Sortlen |
+-------------+---------+------+---------+----------+---------+
Expand All @@ -39,7 +47,10 @@ mysql> SHOW COLLATION;
When new collation framework is enabled, `utf8_general_ci` and `utf8mb4_general_ci` are additionally supported.

```sql
mysql> SHOW COLLATION;
SHOW COLLATION;
```

```
+--------------------+---------+------+---------+----------+---------+
| Collation | Charset | Id | Default | Compiled | Sortlen |
+--------------------+---------+------+---------+----------+---------+
Expand All @@ -58,6 +69,25 @@ mysql> SHOW COLLATION;
11 rows in set (0.001 sec)
```

To filter on the character set, you can add a `WHERE` clause.

```sql
SHOW COLLATION WHERE Charset="utf8mb4";
```

```sql
+--------------------+---------+-----+---------+----------+---------+
| Collation | Charset | Id | Default | Compiled | Sortlen |
+--------------------+---------+-----+---------+----------+---------+
| utf8mb4_0900_ai_ci | utf8mb4 | 255 | | Yes | 1 |
| utf8mb4_0900_bin | utf8mb4 | 309 | | Yes | 1 |
| utf8mb4_bin | utf8mb4 | 46 | Yes | Yes | 1 |
| utf8mb4_general_ci | utf8mb4 | 45 | | Yes | 1 |
| utf8mb4_unicode_ci | utf8mb4 | 224 | | Yes | 1 |
+--------------------+---------+-----+---------+----------+---------+
5 rows in set (0.00 sec)
```

## MySQL compatibility

The usage of the `SHOW COLLATION` statement in TiDB is fully compatible with MySQL. However, charsets in TiDB might have different default collations compared with MySQL. For details, refer to [Compatibility with MySQL](/mysql-compatibility.md). If you find any compatibility differences, [report a bug](https://docs.pingcap.com/tidb/stable/support).
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