Github user qiuchenjian commented on a diff in the pull request:
https://github.com/apache/carbondata/pull/3044#discussion_r244677596
--- Diff: docs/ddl-of-carbondata.md ---
@@ -681,24 +682,28 @@ Users can specify which columns to include and
exclude for local dictionary gene
**NOTE:** Drop Complex child column is not supported.
- - ##### CHANGE DATA TYPE
+ - ##### RENAME COLUMN AND CHANGE DATATYPE
- This command is used to change the data type from INT to BIGINT or
decimal precision from lower to higher.
+ This command is used to change the data type from INT to BIGINT or
decimal precision from lower to higher and rename column.
Change of decimal data type from lower precision to higher precision
will only be supported for cases where there is no data loss.
```
- ALTER TABLE [db_name.]table_name CHANGE col_name col_name
changed_column_type
+ ALTER TABLE [db_name.]table_name CHANGE old_col_name new_col_name
column_data_type
```
+ Scenarios:
+ - If both the old and new column name are same, it is just a datatype
change operation
--- End diff --
```suggestion
- If both the old and new column names are the same, it is just a
datatype change operation
```
---
