In this example, we are changing the owner role of the ‘dataflair’ database using the ALTER statement. It does not provide true DDL but you can use the information provided to build the DDL statement. STORED AS TEXTFILE is to tell Hive what type of file to expect. The metadata information includes column name, column type and column comment. Optionally you can specify a partition spec or column name to return the metadata pertaining to a partition or column respectively. Another command that you can use to get table data types and HDFS location is Describe Formatted/Extended command. The hive partition is similar to table partitioning available in SQL server or any other RDBMS database tables. In this example, we are trying to rename the ‘Employee’ table to ‘Com_Emp’ using the ALTER statement. This command shows meta data about the hive table which includes list of columns,data types and location of the table.There are three ways to describe a table in Hive. Don’t miss Apache Hive Architecture & Components in detail. Don’t know about different Data Types supported by hive? Storage Formats. Stay updated with latest technology trends Join DataFlair on Telegram!! To drop the database with tables, we can use CASCADE. Read Hive Data Types article. AST was removed from EXPLAIN EXTENDED in HIVE-13533 and reinstated as a separate command in HIVE-15932. Currently, Hive supports inner, outer, left, and right joins for two or more tables. It is optional. For a managed (non-external) table, data is manipulated through Hive SQL statements (LOAD DATA, INSERT, etc.) ]materialized_view_name; db_name The database name. Apache Hive is a data warehouse system for Apache Hadoop. While inserting data into Hive, it is better to use LOAD DATA to store bulk records. By default, it uses Text data format. Describe table_name: If you want to see the primary information of the Hive table such as only the list of columns and its data types,the describe command will help you on this. In this video I am explaining about important basic topics such as Create external table, commenting, Alter table, Overwrite, describe table. CREATE TABLE [ IF NOT EXISTS] [db_name. An external table is a table that describes the schema or metadata of external files. In this example, we are setting the database properties of the ‘dataflair’ database after its creation by using the ALTER command. Hive DDL commands are the statements used for defining and changing the structure of a table or database in Hive. The DROP TABLE statement in Hive deletes the data for a particular table and remove all metadata associated with it from Hive metastore. So, Both SCHEMA and DATABASE are same in Hive. Save the program in a file named HiveCreateDb.java. DESCRIBE and DESCRIBE EXTENDED statements can be used for views like for tables, however, for DESCRIBE EXTENDED, the detailed table information has a variable named typeable which has value = ‘virtual view’ for views. Instead, it changes the default parent-directory, where new tables will be added for this database. We can use IF NOT EXISTS to skip the error. Hive allows you to provide structure on largely unstructured data. Get summary, details, and formatted information about the materialized view in the default database and its partitions. We can use DESCRIBE to describe our database. The CREATE DATABASE statement is used to create a database in the Hive. What is Hive Internal or Managed Table? In the below example, we are deleting the ‘employee’ table. Using … If PURGE is not specified then the data is actually moved to the .Trash/current directory. Your email address will not be published. The DATABASE and SCHEMA are interchangeable. Tags: Altering and Dropping TablesCreate Database StatementCreating Hive TablesDrop databaseHive Commandshive commands with examplesHive DDL commandsHive Show Databasetypes of Hive DDL commands, Your email address will not be published. The default behavior is RESTRICT which means that the database is dropped only when it is empty. The primary purpose of defining an external table is to access and execute queries on data stored outside the Hive. DROP TABLE in Hive. ROW FORMAT DELIMITED means we are telling the Hive that when it finds a new line character, that means a new record. No other metadata associated with the database can be changed. The conventions of creating a table in HIVE is quite similar to creating a table using SQL. We will insert the following data into the table. Free Hive Quiz. On successful download, you get to see the following response: Given below is the JDBC program to load given data into the table. Using the ALTER TABLE statement we can rename the table, add columns to the table, change the table properties, etc. expression An expression formed from one or more columns that exist in the tables or views referenced by the query. There are many DDL commands. The easiest way would be using Apache Atlas, if you have Atlas installed, you should be able to see all the table/column metadata, including comments in the … DESCRIBE. ]table_name DESCRIBE DETAIL delta.`` Return information about schema, partitioning, table size, and so on. The advantage of partitioning is that since the data is stored in slices, the query response time becomes faster. The EXTENDED can be used to get the database properties. The DROP TABLE statement in Hive deletes the data for a particular table and remove all metadata associated with it from Hive metastore. Use the following commands to compile and execute this program. Create Table is a statement used to create a table in Hive. Note: The ALTER DATABASE … SET LOCATION statement does not move the database current directory contents to the newly specified location. The following table lists the fields and their data types in employee table: The following data is a Comment, Row formatted fields such as Field terminator, Lines terminator, and Stored File type. table_name [(col_name data_type [COMMENT col_comment], ...)] [COMMENT table_comment] [ROW FORMAT row_format] [STORED AS file_format] Example Let’s start with the DDL commands on Databases in Hive. Other than optimizer, hive uses mentioned statistics in many other ways. For example, you can see the current reader and writer versions of a table. DESCRIBE DATABASE; DESCRIBE QUERY; DESCRIBE … This statement does not change the locations associated with any tables or partitions under the specified database. Generally, after creating a table in SQL, we can insert data using the Insert statement. column_name Optional list of column names in a table or view. DDL DESCRIBE TABLE Example: 4. The SHOW TABLES statement in Hive lists all the base tables and views in the current database. This article will cover each DDL command individually, along with their syntax and examples. The several types of Hive DDL commands are: Before moving forward, note that the Hive commands are case-insensitive. These are the basic HiveQL DDL statements that one should know before working with Hive. The DESCRIBE statement in Hive shows the lists of columns for the specified table. Hive partition is a way to organize a large table into several smaller tables based on one or multiple columns (partition key, for example, date, state e.t.c). By default, Hive creates a table as an Internal table and owned the table structure and the files. SHOW TABLES is used to show both tables and views. Hive supports built-in and custom-developed file formats. query A SELECT statement that defines the columns and rows in the table or view. There are 2 types of tables in Hive, Internal and External. We can use either DATABASE or SCHEMA. Examples. If a table or view already exists with the same name, then the error is thrown. If PURGE is not specified then the data is actually moved to the .Trash/current directory. Still, if you have doubts, feel free to ask in the comment section. In other words, Hive completely manages the lifecycle of the table (metadata & data) similar to tables in RDBMS. AUTHORIZATION is supported from HIVE 0.14.0 via HIVE-5961. It is used to build or modify the tables and other objects in the database. It provides SQL-like access for data in HDFS so that Hadoop can be used as a warehouse structure. Describing Table. Thus in this article, we have studied how to create a database, drop a database, alter a database, etc. DESCRIBE TABLE. Syntax: DESCRIBE DATABASE ; Example: In this article, we are going to learn Hive DDL commands. Follow the Hive-3.1.2 installation guide to install Hive on your system. Hive Describe - Learn Hive in simple and easy steps from basic to advanced concepts with clear examples including Introduction, Architecture, Installation, Data Types, Create Database, Use Database, Alter Database, Drop Database, Tables, Create Table, Alter Table, Load Data to Table, Insert Table, Drop Table, Views, Indexes, Partitioning, Show, Describe, Built-In Operators, Built-In Functions Here in this example, we are creating a database ‘dataflair’. The syntax and example are as follows: Syntax CREATE [TEMPORARY] [EXTERNAL] TABLE [IF NOT EXISTS] [db_name.] ]table_name Like [db_name].existing_table [LOCATION hdfs_path] The following query creates a table named employee using the above data. We can also use DESCRIBE TABLE_NAME, DESCRIBE EXTENDED TABLE_NAME, SHOW CREATE TABLE TABLE_NAME along with DESCRIBE_FORMATTED TABLE_NAME which gives table information in the well-formatted structure. It is used with databases, tables, and view in the hive. The following query loads the given text into the table. The option will show the database location and the other information regarding that database. In this example, we are adding two columns ‘Emp_DOB’ and ‘Emp_Contact’ in the ‘Comp_Emp’ table using the ALTER command. Required fields are marked *, Home About us Contact us Terms and Conditions Privacy Policy Disclaimer Write For Us Success Stories, This site is protected by reCAPTCHA and the Google, Stay updated with latest technology trends, Databases, Tables, Table Properties, Partitions, Functions, Index. Internal table are like normal database table … A view is designated as VIRTUAL_VIEW in DESCRIBE FORMATTED output. schema/database A configured storage plugin instance with or without a configured workspace. The partitioning in Hive means dividing the table into some parts based on the values of a particular column like date, course, city or country. The DESCRIBE DATABASE statement in Hive shows the name of Database in Hive, its comment (if set), and its location on the file system. We can modify multiple numbers of properties associated with the table schema in the Hive. The DROP DATABASE statement in Hive is used to Drop (delete) the database. Hive Create Table Command and Examples; Hive Describe Formatted/Extended Output. Fundamentally, there are two types of tables in HIVE – Managed or Internal tables and external tables. In this example, we are setting the table properties after table creation by using ALTER command. DESCRIBE FORMATTED default.partition_mv_1; Example output is: This chapter explains how to create a table and how to insert data into it. This Free Hive quiz will help you to revise the concepts of Apache Hive.Also will build up your confidence in Hive. Here in this example, we are dropping a database ‘dataflair’ using the DROP statement. If PURGE is specified, then data is lost completely. DESCRIBE DETAIL [db_name. In the hive, we can use describe command to see table structure, its location as well as its table properties. The use of EXTENDED in the EXPLAIN statement produces extra information about the … There is nothing like SHOW VIEWS in Hive. After learning Apache Hive, try your hands on Latest Free Hive Quiz and get to know your learning so far.Below is some multiple choice Questions corresponding to them are the choice of answers. VECTORIZATION is supported from Hive 2.3.0 via HIVE-11394. Introduction to Hive Databases. Create Table Managed and External Tables. The ALTER DATABASE statement in Hive is used to change the metadata associated with the database in Hive. This case study describes creation of internal table, loading data in it, creating views, indexes and dropping table on weather data. But in Hive, we can insert data using the LOAD DATA statement. When you have a hive table, you may want to check its delimiter or detailed information such as Schema. There are two ways to load data: one is from local file system and second is from Hadoop file system. OVERWRITE is optional to overwrite the data in the table. LOCKS is supported from Hive 3.2.0 via HIVE-17683. The syntax and example are as follows: Let us assume you need to create a table named employee using CREATE TABLE statement. Hive lets programmers create a new table by replicating the schema of an existing table but remember only the schema of the new table is replicated but not the data. Hive: Internal Tables. It is a way of dividing a table into related parts based on the values of partitioned columns such as date, city, and department. Internal tables are also known as Managed tables that are owned and managed by Hive. From Hive-0.14.0 release onwards Hive DATABASE is also called as SCHEMA. On successful creation of table, you get to see the following response: The JDBC program to create a table is given example. Related statements. Want to run Hive queries for creating, modifying, dropping, altering tables and databases? Hive is used because the tables in Hive are similar to tables in a relational database. In this table, we are creating a table ‘Employee’ in the ‘dataflair’ database. CREATE DATABASE is the same as create database. The CREATE TABLE statement in Hive is used to create a table with the given name. All the commands discussed below will do the same work for SCHEMA and DATABASE keywords in the syntax. Since this is an external table (EXTERNAL_TABLE), Hive will not keep any stats on the table since it is assumed that another application is changing the underlying data at will.Why keep stats if we can't trust that the data will be the same in another 5 minutes? workspace The location, within a schema, where a table or view exists. Hive provides us the functionality to perform Alteration on the Tables and Databases. The article describes the Hive Data Definition Language(DDL) commands for performing various operations like creating a table/database in Hive, dropping a table/database in Hive, altering a table/database in Hive, etc. Create Table is a statement used to create a table in Hive. Uses of Hive Table or Partition Statistics Hive organizes tables into partitions. We have also studied statements for creating, dropping, altering a table in Hive. LOCAL is identifier to specify the local path. The following commands are used to compile and execute this program. Before we look at the syntax let’s understand how different joins work. The syntax is similar to what we use in SQL. Its data files are stored in an HDFS directory under the default Hive data directory. view_name The unique name of a view. The SHOW DATABASES statement lists all the databases present in the Hive. After you define the structure, you can use Hive to query the data without knowledge of Java or Map Reduce. For column comments, you can simply run the hive command 'DESCRIBE tablename;', and you should see a comment column in the results. The ALTER TABLE statement in Hive enables you to change the structure of an existing table. A table created with no special format or storage clauses is designated as a MANAGED_TABLE (an "internal table" in Impala terminology). Introduction to External Table in Hive. See CompressedStorage for details on... Row Formats & SerDe. FIELDS TERMINATED BY ‘,’ tells Hive what delimiter we are using in our files to separate each column. Describe Table. DESCRIBE transaction; ... To combine and retrieve the records from multiple tables we use Hive Join. It is a text file named sample.txt in /home/user directory. TRUNCATE TABLE statement in Hive removes all the rows from the table or partition. DESCRIBE [EXTENDED | FORMATTED] [db_name. Apache Hive Architecture & Components in detail. Returns the basic metadata information of a table. Partitioning in Hive. For running Hive DDL commands, you must have Hive installed on your system. If you add the option IF NOT EXISTS, Hive ignores the statement in case the table already exists. The USE statement in Hive is used to select the specific database for a session on which all subsequent HiveQL statements would be executed. materialized_view_name The name of the materialized view. ALTER TABLE command can be used to perform alterations on the tables. table_name The unique name of a table. Save the program in a file named HiveLoadData.java. So now, let us go through each of the commands deeply. In this post, we will check Apache Hive table statistics – Hive ANALYZE TABLE command and some examples. Hive uses the statistics such as number of rows in tables or table partition to generate an optimal query plan. There are two solutions: 1. show create table 2. describe extended ; 3. describe formatted ; Creating Internal Table. When creating the new table, the location parameter can be specified.

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