Menu Close

What happens when a managed table is dropped?

What happens when a managed table is dropped?

With a managed table, the underlying directories and data get wiped out when the table is dropped.

What happens when an external table is dropped in hive?

When you drop a table from Hive Metastore, it removes the table/column data and their metadata. It can be a normal table (stored in Metastore) or an external table (stored in local file system); Hive treats both in the same manner, irrespective of their types.

Will retain the table data once the table is dropped?

Re: HIVE: dropping the table does not remove data. When a table is dropped, the data in case of managed tables gets cleaned up. However for an external table only the metadata of the table is cleared and the data still persists as it is in its place.

Can not drop table in hive?

Re: Drop table not working as expected in Hive. The issue is that the DROP TABLE statement doesn’t seem to remove the data from HDFS. This is usually caused by the table being an external table that doesn’t allow Hive to perform all operations on it.

How do I force drop a table in hive?

DROP TABLE [IF EXISTS] table_name [PURGE]; Example: To perform the below operation make sure your hive is running.

How do I delete an existing table in hive?

You can use drop command to delete meta data and actual data from HDFS. And just to delete data and keep the table structure, use truncate command. For further help regarding hive ql, check language manual of hive. Use the following to delete all the tables in a linux environment.

Can we delete a row in Hive table?

Hive doesn’t support updates (or deletes), but it does support INSERT INTO, so it is possible to add new rows to an existing table.

Can we truncate a table in hive?

TRUNCATE Table Command in Hive. This hive command is used to truncate all the rows present in a table i.e. it deletes all the data from the Hive meta store and the data cannot be restored.

Can we truncate managed table in hive?

Truncate Hive target tables to delete the table contents. You can truncate internal and external Hive tables in the Hadoop environment. To truncate the entire Hive table, choose the option to truncate the target table.

What is MSCK repair table in hive?

MSCK REPAIR TABLE recovers all the partitions in the directory of a table and updates the Hive metastore. When creating a table using PARTITIONED BY clause, partitions are generated and registered in the Hive metastore.

How do I drop ORC tables in hive?

Follows the steps.

  1. Check if the table is external. If it isn’t, use the following statement to make it external.
  2. Drop the table. Since the table is an external table, you can drop it without dropping the actual table.
  3. Recreate the table with the new schema. You should be able to access the table with new schema.

How do I delete a row in hive?

Delete can be performed on the table that supports ACID. Instead, you can follow other easy steps such as create hive temporary table and select records from the original table by excluding data that you want to delete from table.

How do you delete all rows in Hive table?

How to use Hive TRUNCATE ?

  1. DELETE : used to delete particular row with where condition and you can all delete all the rows from the given table.
  2. TRUNCATE: used to truncate all the rows, which can not even be restored at all, this actions deletes data in Hive meta store.

Can we update hive external table?

There are many approaches that you can follow to update Hive tables, such as: Use Temporary Hive Table to Update Table. Set TBLPROPERTIES to enable ACID transactions on Hive Tables. Use HBase to update records and create Hive External table to display HBase Table data.

How do I remove a NULL from hive?

Use nvl() function in Hive to replace all NULL values of a column with a default value, In this article, I will explain with an example. Replace all NULL values with -1 or 0 or any number for the integer column. Replace all NULL values with empty space for string types. Replace with any value based on your need.

How do I replace null values with 0 in hive?

You can use coalesce() to replace null values with 0 s: select t1. *, coalesce(t2. Apple, 0) as apple, coalesce(t3.

IS NULL function in hive?

COALESCE() OR ISNULL() in HIVE. If you want convert NULL value to 0 , In SQL we can achieve it by using function ISNULL(columnname,0). In HIVE we don’t have such function , but we can achieve this result using below code. COALESCE(column,CAST(0 AS BIGINT)).

How do I cast a null in hive?

SELECT CAST(regexp_replace(regexp_replace(column1,’\\. ‘,”),’,’,’. ‘) as decimal(12,2)) FROM table_name; the above query return null values.

Is numeric check in hive?

Apache Hive is numeric User Defined Function You can create user defined function to check if string is numeric. Below is the sample python script to identify the numeric values.

How do I cast a query in hive?

Hive CAST function converts the value of an expression to any other type. The result of the function will be NULL in case if function cannot converts to particular data type. You can use this function when passing a column value or literal to a function that expects a parameter with a different data type.

How do you use the between operators in the hive?

BETWEEN operator in HIVE When we have to check if column value lies between a range of value then we use BETWEEN operator in the query. You have to specify MIN and MAX value for the range when using BETWEEN operator.

Is true in hive?

SQL standard defines only three values for boolean: TRUE, FALSE, and UNKNOWN(=NULL in Hive).

How do I get distinct values in hive?

DISTINCT keyword is used in SELECT statement in HIVE to fetch only unique rows. The row does not mean entire row in the table but it means “row” as per column listed in the SELECT statement. If the SELECT has 3 columns listed then SELECT DISTINCT will fetch unique row for those 3 column values only.

How do you not use in hive?

hive> select * from A where id not in (select id from B where id is not null); FAILED: SemanticException [Error 10249]: Line 1:22 Unsupported SubQuery Expression ‘id’: Correlating expression cannot contain unqualified column references.

How do I run a Hive query in putty?

How to Run Hive Scripts?

  1. Step 1: Writing a Hive script. To write the Hive Script the file should be saved with . sql extension.
  2. Step 2: Running the Hive Script. The following is the command to run the Hive script: Command: hive –f /home/cloudera/sample.sql.

Does hive require Hadoop?

1 Answer. Hive provided JDBC driver to query hive like JDBC, however if you are planning to run Hive queries on production system, you need Hadoop infrastructure to be available. Hive queries eventually converts into map-reduce jobs and HDFS is used as data storage for Hive tables.

How do you automate a Hive query?

Like you can also use Hive CLI and its very ease to do such jobs. You can write shell script in Linux or . bat in Windows. In script you can simply go like below entries.

How do I run Hive query in oozie?

Run Hive Jobs with Oozie

  1. Specify the hive-site. xml in the job-xml parameter.
  2. Specify the name of the script (for example, script. q ) that contains the hive query in the script parameter.
  3. Optionally, add properties used by the Oozie launcher job. Add the prefix oozie. launcher to the property names.

How do I connect to hive from command line?

To connect to Hive running on remote cluster, just pass the IP address and Port on JDBC connection string. By not providing a username and password, it prompts for the credentials to enter. In case if you are running on LOCAL, you can also try with the localhost, hostname, or 127.0. 0.1 instead of remote IP address.

How do I start the hive shell in Linux?

How to Get Started with Hive on Cloudera

  1. Create a folder with any name on the Cloudera Vm desktop. For this example, I have named it himanshuHive.
  2. Open terminal and execute the command: cloudera@cloudera-vm:/home/cloudera# > sudo su.
  3. Type this command to enter into Hive shell: sudo hive.