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

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Description

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

RENAME

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

Syntax

{% highlight sql %} ALTER TABLE [db_name.]old_table_name RENAME TO [db_name.]new_table_name

ALTER TABLE table_name PARTITION partition_spec RENAME TO PARTITION partition_spec;

{% endhighlight %}

Parameters

old_table_name

Name of an existing table.

db_name

Name of the existing database.

new_table_name

New name using which the table has to be renamed.

partition_spec

Partition to be renamed.

ADD COLUMNS

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

Syntax

{% highlight sql %} ALTER TABLE table_name ADD COLUMNS (col_spec[, col_spec ...]) {% endhighlight %}

Parameters

table_name

The name of an existing table.

COLUMNS (col_spec)

Specifies the columns to be added to be renamed.

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

{% highlight sql %}

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

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

{% endhighlight %}

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

{% highlight sql %}

--Set SERDE Properties ALTER TABLE table_name [PARTITION part_spec] SET SERDEPROPERTIES (key1=val1, key2=val2, ...)

ALTER TABLE table_name [PARTITION part_spec] SET SERDE serde_class_name [WITH SERDEPROPERTIES (key1=val1, key2=val2, ...)]

{% endhighlight %}

SET LOCATION And SET FILE FORMAT

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

Syntax

{% highlight sql %}

--Changing File Format ALTER TABLE table_name [PARTITION partition_spec] SET FILEFORMAT file_format;

--Changing File Location ALTER TABLE table_name [PARTITION partition_spec] SET LOCATION 'new_location';

{% endhighlight %}

Parameters

table_name

The name of an existing table.

PARTITION (part_spec)

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

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

Specifies the SERDE properties to be set.

Examples

{% highlight 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 column 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 | +--------------------------+------------+----------+--+

--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.madoop' WITH SERDEPROPERTIES ('k' = 'v', 'kay' = 'vee')

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

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

{% endhighlight %}

Related Statements

• CREATE TABLE
• DROP TABLE