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59 lines
1.4 KiB
Markdown
59 lines
1.4 KiB
Markdown
---
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toc_priority: 51
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toc_title: COMMENT
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---
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# ALTER TABLE … MODIFY COMMENT {#alter-modify-comment}
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Adds, modifies, or removes comment to the table, regardless if it was set before or not. Comment change is reflected in both [system.tables](../../../operations/system-tables/tables.md) and `SHOW CREATE TABLE` query.
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**Syntax**
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``` sql
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ALTER TABLE [db].name [ON CLUSTER cluster] MODIFY COMMENT 'Comment'
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```
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**Examples**
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Creating a table with comment (for more information, see the [COMMENT] clause(../../../sql-reference/statements/create/table.md#comment-table)):
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``` sql
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CREATE TABLE table_with_comment
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(
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`k` UInt64,
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`s` String
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)
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ENGINE = Memory()
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COMMENT 'The temporary table';
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```
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Modifying the table comment:
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``` sql
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ALTER TABLE table_with_comment MODIFY COMMENT 'new comment on a table';
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SELECT comment FROM system.tables WHERE database = currentDatabase() AND name = 'table_with_comment';
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```
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Output of a new comment:
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```text
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┌─comment────────────────┐
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│ new comment on a table │
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└────────────────────────┘
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```
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Removing the table comment:
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``` sql
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ALTER TABLE table_with_comment MODIFY COMMENT '';
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SELECT comment FROM system.tables WHERE database = currentDatabase() AND name = 'table_with_comment';
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```
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Output of a removed comment:
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```text
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┌─comment─┐
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│ │
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└─────────┘
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```
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