huaxingao commented on a change in pull request #27779: [SPARK-30962][DOC]Documentation for Alter table command phase 2 URL: https://github.com/apache/spark/pull/27779#discussion_r388008600
########## File path: docs/sql-ref-syntax-ddl-alter-table.md ########## @@ -83,6 +82,108 @@ ALTER TABLE table_identifier ADD COLUMNS ( col_spec [ , col_spec ... ] ) </dl> +### ALTER OR CHANGE COLUMN +`ALTER TABLE ALTER COLUMN` or `ALTER TABLE CHANGE COLUMN` statement changes column's comment. + +#### Syntax +{% highlight sql %} +ALTER TABLE table_identifier { ALTER | CHANGE } COLUMN col_spec alterColumnAction +{% endhighlight %} + +#### Parameters +<dl> + <dt><code><em>table_identifier</em></code></dt> + <dd> + Specifies a table name, which may be optionally qualified with a database name.<br><br> + <b>Syntax:</b> + <code> + [ database_name. ] table_name + </code> + </dd> +</dl> + +<dl> + <dt><code><em>COLUMN col_spec</em></code></dt> + <dd>Specifies the columns to be altered to be changed.</dd> +</dl> + +<dl> + <dt><code><em>alterColumnAction</em></code></dt> + <dd> + Change the comment string.<br><br> Review comment: I saw the following in ```SqlBase.g4```. Can ```alterColumnAction``` change type, colPosition, setOrDrop as well? ``` alterColumnAction : TYPE dataType | commentSpec | colPosition | setOrDrop=(SET | DROP) NOT NULL ; ``` ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For additional commands, e-mail: reviews-h...@spark.apache.org