# ALTER TABLE REPLACE COLUMNS
<a name="alter-table-replace-columns"></a>

Removes all existing columns from a table created with the [LazySimpleSerDe](lazy-simple-serde.md) and replaces them with the set of columns specified. When the optional `PARTITION` syntax is used, updates partition metadata. You can also use `ALTER TABLE REPLACE COLUMNS` to drop columns by specifying only the columns that you want to keep.

## Synopsis
<a name="synopsis"></a>

```
ALTER TABLE table_name 
  [PARTITION 
   (partition_col1_name = partition_col1_value
   [,partition_col2_name = partition_col2_value][,...])]
  REPLACE COLUMNS (col_name data_type [, col_name data_type, ...])
```

## Parameters
<a name="parameters"></a>

**PARTITION (partition\$1col\$1name = partition\$1col\$1value [,...])**  
Specifies a partition with the column name/value combinations that you specify. Enclose `partition_col_value` in quotation marks only if the data type of the column is a string.

**REPLACE COLUMNS (col\$1name data\$1type [,col\$1name data\$1type,...])**  
Replaces existing columns with the column names and datatypes specified.

## Notes
<a name="alter-table-replace-columns-notes"></a>
+ To see the change in table columns in the Athena Query Editor navigation pane after you run `ALTER TABLE REPLACE COLUMNS`, you might have to manually refresh the table list in the editor, and then expand the table again.
+ `ALTER TABLE REPLACE COLUMNS` does not work for columns with the `date` datatype. To workaround this issue, use the `timestamp` datatype in the table instead.
+ Note that even if you are replacing just a single column, the syntax must be `ALTER TABLE table-name REPLACE COLUMNS`, with *columns* in the plural. You must specify not only the column that you want to replace, but the columns that you want to keep – if not, the columns that you do not specify will be dropped. This syntax and behavior derives from Apache Hive DDL. For reference, see [Add/Replace columns](https://cwiki.apache.org/confluence/display/Hive/LanguageManual+DDL#LanguageManualDDL-Add/ReplaceColumns) in the Apache documentation. 

## Example
<a name="alter-table-replace-columns-example"></a>

In the following example, the table `names_cities`, which was created using the [LazySimpleSerDe](lazy-simple-serde.md), has three columns named `col1`, `col2`, and `col3`. All columns are of type `string`. To show the columns in the table, the following command uses the [SHOW COLUMNS](show-columns.md) statement.

```
SHOW COLUMNS IN names_cities
```

Result of the query:

```
col1
col2
col3
```

The following `ALTER TABLE REPLACE COLUMNS` command replaces the column names with `first_name`, `last_name`, and `city`. The underlying source data is not affected.

```
ALTER TABLE names_cities
REPLACE COLUMNS (first_name string, last_name string, city string)
```

To test the result, `SHOW COLUMNS` is run again.

```
SHOW COLUMNS IN names_cities
```

Result of the query:

```
first_name
last_name
city
```

Another way to show the new column names is to [preview the table](creating-tables-showing-table-information.md) in the Athena Query Editor or run your own `SELECT` query.