spark-instrumented-optimizer/docs/sql-ref-syntax-ddl-alter-table.md

---
layout: global
title: ALTER TABLE
displayTitle: ALTER TABLE
license: |
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  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
  (the "License"); you may not use this file except in compliance with
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---

### Description

`ALTER TABLE` statement changes the schema or properties of a table.

### RENAME 

`ALTER TABLE RENAME TO` statement changes the table name of an existing table in the database.

#### Syntax

```sql
ALTER TABLE table_identifier RENAME TO table_identifier

ALTER TABLE table_identifier partition_spec RENAME TO partition_spec
```

#### Parameters

* **table_identifier**

    Specifies a table name, which may be optionally qualified with a database name.

    **Syntax:** `[ database_name. ] table_name`

* **partition_spec**

    Partition to be renamed.

    **Syntax:** `PARTITION ( partition_col_name  = partition_col_val [ , ... ] )`

### ADD COLUMNS

`ALTER TABLE ADD COLUMNS` statement adds mentioned columns to an existing table.

#### Syntax

```sql
ALTER TABLE table_identifier ADD COLUMNS ( col_spec [ , ... ] )
```

#### Parameters

* **table_identifier**

    Specifies a table name, which may be optionally qualified with a database name.

    **Syntax:** `[ database_name. ] table_name`

* **COLUMNS ( col_spec )**

    Specifies the columns to be added.

### ALTER OR CHANGE COLUMN

`ALTER TABLE ALTER COLUMN` or `ALTER TABLE CHANGE COLUMN` statement changes column's definition.

#### Syntax

```sql
ALTER TABLE table_identifier { ALTER | CHANGE } [ COLUMN ] col_spec alterColumnAction
```

#### Parameters

* **table_identifier**

    Specifies a table name, which may be optionally qualified with a database name.

    **Syntax:** `[ database_name. ] table_name`

* **COLUMNS ( col_spec )**

    Specifies the column to be altered or be changed.

* **alterColumnAction**

    Change column's definition.

### ADD AND DROP PARTITION

#### ADD PARTITION

`ALTER TABLE ADD` statement adds partition to the partitioned table.

##### Syntax

```sql
ALTER TABLE table_identifier ADD [IF NOT EXISTS] 
    ( partition_spec [ partition_spec ... ] )
```
     
##### Parameters

* **table_identifier**

    Specifies a table name, which may be optionally qualified with a database name.

    **Syntax:** `[ database_name. ] table_name`

* **partition_spec**

    Partition to be added.

    **Syntax:** `PARTITION ( partition_col_name  = partition_col_val [ , ... ] )`

#### DROP PARTITION

`ALTER TABLE DROP` statement drops the partition of the table.

##### Syntax

```sql
ALTER TABLE table_identifier DROP [ IF EXISTS ] partition_spec [PURGE]
```
     
##### Parameters

* **table_identifier**

    Specifies a table name, which may be optionally qualified with a database name.

    **Syntax:** `[ database_name. ] table_name`

* **partition_spec**

    Partition to be dropped.

    **Syntax:** `PARTITION ( partition_col_name  = partition_col_val [ , ... ] )`
     
### SET AND UNSET

#### SET TABLE PROPERTIES

`ALTER TABLE SET` command is used for setting the table properties. If a particular property was already set, 
this overrides the old value with the new one.

`ALTER TABLE UNSET` is used to drop the table property. 

##### Syntax

```sql
-- Set Table Properties 
ALTER TABLE table_identifier SET TBLPROPERTIES ( key1 = val1, key2 = val2, ... )

-- Unset Table Properties
ALTER TABLE table_identifier UNSET TBLPROPERTIES [ IF EXISTS ] ( key1, key2, ... )
```

#### SET SERDE

`ALTER TABLE SET` command is used for setting the SERDE or SERDE properties in Hive tables. If a particular property was already set, this overrides the old value with the new one.

##### Syntax

```sql
-- Set SERDE Properties
ALTER TABLE table_identifier [ partition_spec ]
    SET SERDEPROPERTIES ( key1 = val1, key2 = val2, ... )

ALTER TABLE table_identifier [ partition_spec ] SET SERDE serde_class_name
    [ WITH SERDEPROPERTIES ( key1 = val1, key2 = val2, ... ) ]
```

#### SET LOCATION And SET FILE FORMAT

`ALTER TABLE SET` command can also be used for changing the file location and file format for 
existing tables. 

##### Syntax

```sql
-- Changing File Format
ALTER TABLE table_identifier [ partition_spec ] SET FILEFORMAT file_format

-- Changing File Location
ALTER TABLE table_identifier [ partition_spec ] SET LOCATION 'new_location'
```

#### Parameters

* **table_identifier**

    Specifies a table name, which may be optionally qualified with a database name.

    **Syntax:** `[ database_name. ] table_name`

* **partition_spec**

    Specifies the partition on which the property has to be set.

    **Syntax:** `PARTITION ( partition_col_name  = partition_col_val [ , ... ] )`

* **SERDEPROPERTIES ( key1 = val1, key2 = val2, ... )**

    Specifies the SERDE properties to be set.

### Examples

```sql
-- RENAME table 
DESC student;
+-----------------------+---------+-------+
|               col_name|data_type|comment|
+-----------------------+---------+-------+
|                   name|   string|   NULL|
|                 rollno|      int|   NULL|
|                    age|      int|   NULL|
|# Partition Information|         |       |
|             # col_name|data_type|comment|
|                    age|      int|   NULL|
+-----------------------+---------+-------+

ALTER TABLE Student RENAME TO StudentInfo;

-- After Renaming the table
DESC StudentInfo;
+-----------------------+---------+-------+
|               col_name|data_type|comment|
+-----------------------+---------+-------+
|                   name|   string|   NULL|
|                 rollno|      int|   NULL|
|                    age|      int|   NULL|
|# Partition Information|         |       |
|             # col_name|data_type|comment|
|                    age|      int|   NULL|
+-----------------------+---------+-------+

-- RENAME partition

SHOW PARTITIONS StudentInfo;
+---------+
|partition|
+---------+
|   age=10|
|   age=11|
|   age=12|
+---------+

ALTER TABLE default.StudentInfo PARTITION (age='10') RENAME TO PARTITION (age='15');

-- After renaming Partition
SHOW PARTITIONS StudentInfo;
+---------+
|partition|
+---------+
|   age=11|
|   age=12|
|   age=15|
+---------+

-- Add new columns to a table
DESC StudentInfo;
+-----------------------+---------+-------+
|               col_name|data_type|comment|
+-----------------------+---------+-------+
|                   name|   string|   NULL|
|                 rollno|      int|   NULL|
|                    age|      int|   NULL|
|# Partition Information|         |       |
|             # col_name|data_type|comment|
|                    age|      int|   NULL|
+-----------------------+---------+-------+

ALTER TABLE StudentInfo ADD columns (LastName string, DOB timestamp);

-- After Adding New columns to the table
DESC StudentInfo;
+-----------------------+---------+-------+
|               col_name|data_type|comment|
+-----------------------+---------+-------+
|                   name|   string|   NULL|
|                 rollno|      int|   NULL|
|               LastName|   string|   NULL|
|                    DOB|timestamp|   NULL|
|                    age|      int|   NULL|
|# Partition Information|         |       |
|             # col_name|data_type|comment|
|                    age|      int|   NULL|
+-----------------------+---------+-------+

-- Add a new partition to a table 
SHOW PARTITIONS StudentInfo;
+---------+
|partition|
+---------+
|   age=11|
|   age=12|
|   age=15|
+---------+

ALTER TABLE StudentInfo ADD IF NOT EXISTS PARTITION (age=18);

-- After adding a new partition to the table
SHOW PARTITIONS StudentInfo;
+---------+
|partition|
+---------+
|   age=11|
|   age=12|
|   age=15|
|   age=18|
+---------+

-- Drop a partition from the table 
SHOW PARTITIONS StudentInfo;
+---------+
|partition|
+---------+
|   age=11|
|   age=12|
|   age=15|
|   age=18|
+---------+

ALTER TABLE StudentInfo DROP IF EXISTS PARTITION (age=18);

-- After dropping the partition of the table
SHOW PARTITIONS StudentInfo;
+---------+
|partition|
+---------+
|   age=11|
|   age=12|
|   age=15|
+---------+

-- Adding multiple partitions to the table
SHOW PARTITIONS StudentInfo;
+---------+
|partition|
+---------+
|   age=11|
|   age=12|
|   age=15|
+---------+

ALTER TABLE StudentInfo ADD IF NOT EXISTS PARTITION (age=18) PARTITION (age=20);

-- After adding multiple partitions to the table
SHOW PARTITIONS StudentInfo;
+---------+
|partition|
+---------+
|   age=11|
|   age=12|
|   age=15|
|   age=18|
|   age=20|
+---------+

-- ALTER OR CHANGE COLUMNS
DESC StudentInfo;
+-----------------------+---------+-------+
|               col_name|data_type|comment|
+-----------------------+---------+-------+
|                   name|   string|   NULL|
|                 rollno|      int|   NULL|
|               LastName|   string|   NULL|
|                    DOB|timestamp|   NULL|
|                    age|      int|   NULL|
|# Partition Information|         |       |
|             # col_name|data_type|comment|
|                    age|      int|   NULL|
+-----------------------+---------+-------+

ALTER TABLE StudentInfo ALTER COLUMN name COMMENT "new comment";

--After ALTER or CHANGE COLUMNS
DESC StudentInfo;
+-----------------------+---------+-----------+
|               col_name|data_type|    comment|
+-----------------------+---------+-----------+
|                   name|   string|new comment|
|                 rollno|      int|       NULL|
|               LastName|   string|       NULL|
|                    DOB|timestamp|       NULL|
|                    age|      int|       NULL|
|# Partition Information|         |           |
|             # col_name|data_type|    comment|
|                    age|      int|       NULL|
+-----------------------+---------+-----------+

-- Change the fileformat
ALTER TABLE loc_orc SET fileformat orc;

ALTER TABLE p1 partition (month=2, day=2) SET fileformat parquet;

-- Change the file Location
ALTER TABLE dbx.tab1 PARTITION (a='1', b='2') SET LOCATION '/path/to/part/ways'

-- SET SERDE/ SERDE Properties
ALTER TABLE test_tab SET SERDE 'org.apache.hadoop.hive.serde2.columnar.LazyBinaryColumnarSerDe';

ALTER TABLE dbx.tab1 SET SERDE 'org.apache.hadoop' WITH SERDEPROPERTIES ('k' = 'v', 'kay' = 'vee')

-- SET TABLE PROPERTIES
ALTER TABLE dbx.tab1 SET TBLPROPERTIES ('winner' = 'loser');

-- SET TABLE COMMENT Using SET PROPERTIES
ALTER TABLE dbx.tab1 SET TBLPROPERTIES ('comment' = 'A table comment.');

-- Alter TABLE COMMENT Using SET PROPERTIES
ALTER TABLE dbx.tab1 SET TBLPROPERTIES ('comment' = 'This is a new comment.');

-- DROP TABLE PROPERTIES
ALTER TABLE dbx.tab1 UNSET TBLPROPERTIES ('winner');
```

### Related Statements

* [CREATE TABLE](sql-ref-syntax-ddl-create-table.html)
* [DROP TABLE](sql-ref-syntax-ddl-drop-table.html)