ALTER TABLE (Databricks SQL)

Alters the schema or properties of a table.

Table name parameter

The table name parameter in all statements has the following form:

• table_name

  Identifies the table. The name must not include a temporal specification.

ADD COLUMNS

Adds columns to an existing table.

Syntax

ALTER TABLE table_name ADD COLUMNS ( col_spec [ , ... ] )

For ADD COLUMNS syntax specific to Delta tables, see Delta table options.

Parameters

• COLUMNS ( col_spec )

  The columns to be added.

ADD AND DROP PARTITION

ADD PARTITION

Adds a partition to the partitioned table.

Syntax

ALTER TABLE table_name ADD [IF NOT EXISTS]
    ( partition_spec [...] )

partition_spec
  PARTITION ( { partition_col_name1  = partition_col_val1 } [ , ... ] )

Parameters

• partition_spec

  Partition to be added.

• IF EXISTS

  Do not throw an exception if the partition does not exist.

DROP PARTITION

Drops the partition of the table.

Syntax

ALTER TABLE table_name DROP [ IF EXISTS ] partition_spec [PURGE]

partition_spec
  PARTITION ( { partition_col_name1  = partition_col_val1 } [ , ... ] )

Parameters

• partition_spec

  Partition to be dropped.

RENAME TO

Changes the name of an existing table in the database.

Syntax

ALTER TABLE table_name partition_spec RENAME TO partition_spec

partition_spec
    PARTITION ( { partition_col_name1 = partition_col_val1 } [ , ... ] )

Parameters

• partition_spec

  Partition to be renamed.

SET AND UNSET

SET TABLE PROPERTIES

Sets and unsets table properties. If a property was already set, overrides the old value with the new one.

Syntax

-- Set Table Properties
ALTER TABLE table_name SET TBLPROPERTIES ( { key1 = val1 } [, ...] )

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

Parameters

• TBLPROPERTIES ( key1 = val1, key2 = val2, … )

  The table properties to be set or unset.

• IF EXISTS

  Do not throw an exception if the property does not exist.

Example: Set a table comment

To set a table comment, run:

ALTER TABLE table_name SET TBLPROPERTIES ('comment' = 'A table comment.')

SET LOCATION

Changes the location of the table definition. Files are moved to the new location, not copied.

Syntax

-- Change file location
ALTER TABLE table_identifier [ partition_spec ] SET LOCATION 'new_location'

Parameters

• partition_spec

  The partition on which the property has to be set.

• new_location

  The path to the location of the table files.

Delta table options

In addition to the standard ALTER TABLE options, Delta tables support the options described in this section.

For add, change, and replace column examples, see Explicitly update schema.

ADD COLUMNS

Adds columns to an existing table including adding nested columns. If a column with the same name already exists in the table or the same nested struct, an exception is thrown.

Syntax

ALTER TABLE table_name ADD COLUMNS ( { columns_name data_type [COMMENT column_comment] [FIRST|AFTER colA_name] } [, ...])

ALTER TABLE table_name ADD COLUMNS ( { column_name.nested_col_name data_type [COMMENT column_comment] [FIRST|AFTER colA_name] } [, ...])

For add columns examples, see Add columns.

CHANGE COLUMN

Changes a column definition of an existing table. You can change the data type, comment, or nullability of a column and reorder columns.

Syntax

ALTER TABLE table_name (ALTER|CHANGE) [COLUMN] alterColumnAction

ALTER TABLE table_name (ALTER|CHANGE) [COLUMN] alterColumnAction

alterColumnAction
 { TYPE dataType
   [COMMENT col_comment]
   [ FIRST | AFTER colA_name]
   {SET | DROP} NOT NULL }

Note

• You can change a column type only in Delta tables.
• You can change the type from Byte -> Short -> Integer without a data rewrite. All other type changes require you to rewrite the data.

For change column examples, see Change column comment or ordering. Also see Constraints.

CHANGE COLUMN (Hive syntax)

Changes a column definition of an existing table. You can change the comment of the column and reorder columns.

Syntax

ALTER TABLE table_name CHANGE [COLUMN] column_name column_name data_type [COMMENT column_comment] [FIRST | AFTER colA_name]

ALTER TABLE table_name CHANGE [COLUMN] column_name.nested_col_name column_name data_type [COMMENT column_comment] [FIRST | AFTER colA_name]

Note

You cannot use CHANGE COLUMN:

• To change the contents of complex data types such as structs. Instead use ADD COLUMNS to add new columns to nested fields, or ALTER COLUMN to change the properties of a nested column.
• To relax the nullability of a column. Instead use ALTER TABLE table_name ALTER COLUMN column_name DROP NOT NULL.

REPLACE COLUMNS

Replaces the column definitions of an existing table. It supports changing the comments of columns, adding columns, and reordering columns. If specified column definitions are not compatible with the existing definitions, an exception is thrown.

Syntax

ALTER TABLE table_name REPLACE COLUMNS ( { column_name1 column_type1 [COMMENT col_comment1] } [, ...] )

For replace columns examples, see Replace columns.

Examples

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

-- 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 articles

• CREATE TABLE
• DROP TABLE
• ALTER VIEW