Saturday, November 12, 2016

Hive Practice Lab 2

Welcome one and all to hive learning session 2

In this post we are going to learn about Altering and droping Tables in hive

I guess you already install hadoop and hive
if not
Install hadoop using the steps mention here > Hadoop Installation
To install hive please go through these steps > Hive Installation

once you installed both of above we are ready to start our hive learning session 2 after completion of basic learning

Alter Options :
what we have earlier

First we are going to alter table name i.e from invites to invite;

ALTER TABLE table_name RENAME TO new_table_name

hive> ALTER TABLE invites RENAME TO invite;
hive> show tables;

Now adding new column to it new_col
(please check output screenshot)

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

hive> ALTER TABLE invite ADD COLUMNS (new_col INT);
hive> show tables;

here we are changing column name (please find output screen shot)

ALTER TABLE table_name CHANGE column_name new_name new_type

hive>ALTER TABLE invite CHANGE new_col changed_column string;

hive> ALTER TABLE invites REPLACE COLUMNS(foo INT, bar STRING, baz INT COMMENT 'baz replaces new_col2');

Note that REPLACE COLUMNS replaces all existing columns and only changes
the table's schema, not the data. The table must use a native SerDe.
REPLACE COLUMNS can also be used to drop columns from the table's schema:

Dropping tables:
hive> DROP TABLE pokes;
pokes table is droped

Comment below for post improvement and you suggestion

Reference :

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