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 use either DATABASE or SCHEMA. Hive supports built-in and custom-developed file formats. In this post, we will check Apache Hive table statistics – Hive ANALYZE TABLE command and some examples. For example, you can see the current reader and writer versions of a table. The DROP DATABASE statement in Hive is used to Drop (delete) the database. Its data files are stored in an HDFS directory under the default Hive data directory. Still, if you have doubts, feel free to ask in the comment section. Other than optimizer, hive uses mentioned statistics in many other ways. The metadata information includes column name, column type and column comment. LOCAL is identifier to specify the local path. If you add the option IF NOT EXISTS, Hive ignores the statement in case the table already exists. No other metadata associated with the database can be changed. The USE statement in Hive is used to select the specific database for a session on which all subsequent HiveQL statements would be executed. The default behavior is RESTRICT which means that the database is dropped only when it is empty. schema/database A configured storage plugin instance with or without a configured workspace. Storage Formats. The syntax and example are as follows: Let us assume you need to create a table named employee using CREATE TABLE statement. In this video I am explaining about important basic topics such as Create external table, commenting, Alter table, Overwrite, describe table. 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? This article will cover each DDL command individually, along with their syntax and examples. Note: The ALTER DATABASE … SET LOCATION statement does not move the database current directory contents to the newly specified location. The use of EXTENDED in the EXPLAIN statement produces extra information about the … AUTHORIZATION is supported from HIVE 0.14.0 via HIVE-5961. view_name The unique name of a view. For a managed (non-external) table, data is manipulated through Hive SQL statements (LOAD DATA, INSERT, etc.) Hive Create Table Command and Examples; Hive Describe Formatted/Extended Output. The syntax is similar to what we use in SQL. The DROP TABLE statement in Hive deletes the data for a particular table and remove all metadata associated with it from Hive metastore. Hive: Internal Tables. 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. In this example, we are setting the database properties of the ‘dataflair’ database after its creation by using the ALTER command. 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. The SHOW DATABASES statement lists all the databases present in the Hive. expression An expression formed from one or more columns that exist in the tables or views referenced by the query. The DATABASE and SCHEMA are interchangeable. Partitioning in Hive. Uses of Hive Table or Partition Statistics Create Table is a statement used to create a table in Hive. 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 Hive allows you to provide structure on largely unstructured data. Save the program in a file named HiveLoadData.java. Syntax: DESCRIBE DATABASE ; Example: In this example, we are changing the owner role of the ‘dataflair’ database using the ALTER statement. Follow the Hive-3.1.2 installation guide to install Hive on your system. column_name Optional list of column names in a table or view. Read Hive Data Types article. workspace The location, within a schema, where a table or view exists. What is Hive Internal or Managed Table? In the below example, we are deleting the ‘employee’ table. So, Both SCHEMA and DATABASE are same in Hive. 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. For running Hive DDL commands, you must have Hive installed on your system. AST was removed from EXPLAIN EXTENDED in HIVE-13533 and reinstated as a separate command in HIVE-15932. The DESCRIBE statement in Hive shows the lists of columns for the specified table. If PURGE is not specified then the data is actually moved to the .Trash/current directory. Using the ALTER TABLE statement we can rename the table, add columns to the table, change the table properties, etc. DDL DESCRIBE TABLE Example: 4. Introduction to Hive Databases. Related statements. Hive is used because the tables in Hive are similar to tables in a relational database. On successful download, you get to see the following response: Given below is the JDBC program to load given data into the table. DESCRIBE FORMATTED default.partition_mv_1; Example output is: There are 2 types of tables in Hive, Internal and External. These are the basic HiveQL DDL statements that one should know before working with Hive. Here in this example, we are dropping a database ‘dataflair’ using the DROP statement. The SHOW TABLES statement in Hive lists all the base tables and views in the current database. Instead, it changes the default parent-directory, where new tables will be added for this database. It is a text file named sample.txt in /home/user directory. The DROP TABLE statement in Hive deletes the data for a particular table and remove all metadata associated with it from Hive metastore. When creating the new table, the location parameter can be specified. In this article, we are going to learn Hive DDL commands. From Hive-0.14.0 release onwards Hive DATABASE is also called as SCHEMA. query A SELECT statement that defines the columns and rows in the table or view. Before we look at the syntax let’s understand how different joins work. We can use IF NOT EXISTS to skip the error. Don’t know about different Data Types supported by hive? The several types of Hive DDL commands are: Before moving forward, note that the Hive commands are case-insensitive. DESCRIBE DETAIL [db_name. The following query loads the given text into the table. ]table_name DESCRIBE DETAIL delta.`` Return information about schema, partitioning, table size, and so on. We can modify multiple numbers of properties associated with the table schema in the Hive. The ALTER TABLE statement in Hive enables you to change the structure of an existing table. The conventions of creating a table in HIVE is quite similar to creating a table using SQL. There are many DDL commands. On successful creation of table, you get to see the following response: The JDBC program to create a table is given example. It is used to build or modify the tables and other objects in the database. There are two solutions: 1. show create table 2. describe extended ; 3. describe formatted ; In this example, we are setting the table properties after table creation by using ALTER command. Using … In other words, Hive completely manages the lifecycle of the table (metadata & data) similar to tables in RDBMS. In this example, we are trying to rename the ‘Employee’ table to ‘Com_Emp’ using the ALTER statement. 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. OVERWRITE is optional to overwrite the data in the 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). Hive provides us the functionality to perform Alteration on the Tables and Databases. To drop the database with tables, we can use CASCADE. A view is designated as VIRTUAL_VIEW in DESCRIBE FORMATTED output. DESCRIBE [EXTENDED | FORMATTED] [db_name. 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. 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. The following query creates a table named employee using the above data. It does not provide true DDL but you can use the information provided to build the DDL statement. Creating Internal Table. Use the following commands to compile and execute this program. CREATE DATABASE is the same as create database. It is a way of dividing a table into related parts based on the values of partitioned columns such as date, city, and department. In this table, we are creating a table ‘Employee’ in the ‘dataflair’ database. The advantage of partitioning is that since the data is stored in slices, the query response time becomes faster. See CompressedStorage for details on... Row Formats & SerDe. Generally, after creating a table in SQL, we can insert data using the Insert statement. CREATE TABLE [ IF NOT EXISTS] [db_name. ROW FORMAT DELIMITED means we are telling the Hive that when it finds a new line character, that means a new record. This Free Hive quiz will help you to revise the concepts of Apache Hive.Also will build up your confidence in Hive. Don’t miss Apache Hive Architecture & Components in detail. table_name [(col_name data_type [COMMENT col_comment], ...)] [COMMENT table_comment] [ROW FORMAT row_format] [STORED AS file_format] Example Thus in this article, we have studied how to create a database, drop a database, alter a database, etc. An external table is a table that describes the schema or metadata of external files. SHOW TABLES is used to show both tables and views. In this example, we are adding two columns ‘Emp_DOB’ and ‘Emp_Contact’ in the ‘Comp_Emp’ table using the ALTER command. All the commands discussed below will do the same work for SCHEMA and DATABASE keywords in the syntax. Want to run Hive queries for creating, modifying, dropping, altering tables and databases? This case study describes creation of internal table, loading data in it, creating views, indexes and dropping table on weather data. Your email address will not be published. The CREATE DATABASE statement is used to create a database in the Hive. It provides SQL-like access for data in HDFS so that Hadoop can be used as a warehouse structure. We have also studied statements for creating, dropping, altering a table in Hive. The CREATE TABLE statement in Hive is used to create a table with the given name. Hive uses the statistics such as number of rows in tables or table partition to generate an optimal query plan. The syntax and example are as follows: Syntax CREATE [TEMPORARY] [EXTERNAL] TABLE [IF NOT EXISTS] [db_name.] Create Table Managed and External Tables. Create Table is a statement used to create a table in Hive. table_name The unique name of a table. Introduction to External Table in Hive. In the hive, we can use describe command to see table structure, its location as well as its table properties. Internal tables are also known as Managed tables that are owned and managed by Hive. Optionally you can specify a partition spec or column name to return the metadata pertaining to a partition or column respectively. DESCRIBE TABLE. ALTER TABLE command can be used to perform alterations on the tables. DESCRIBE transaction; ... To combine and retrieve the records from multiple tables we use Hive Join. The primary purpose of defining an external table is to access and execute queries on data stored outside the Hive. Returns the basic metadata information of a table. Fundamentally, there are two types of tables in HIVE – Managed or Internal tables and external tables. The hive partition is similar to table partitioning available in SQL server or any other RDBMS database tables. But in Hive, we can insert data using the LOAD DATA statement. Apache Hive Architecture & Components in detail. While inserting data into Hive, it is better to use LOAD DATA to store bulk records.
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