hive describe table columns

It is used to make changes to the existing table: DESCRIBE: It describes the table columns: TRUNCATE: Used to permanently truncate and delete the rows of table: DELETE: Deletes the table data, but, can be restored: Go to Hive shell by giving the command sudo hive and enter the command ‘create database’ to create the new database in the Hive. The DESCRIBE statement displays metadata about a table, such as the column names and their data types. At the back end, it has to be … Table definition must include the table name and the attributes of its columns. DESCRIBE EXTENDED table_name. The hive partition is similar to table partitioning available in SQL server or any other RDBMS database tables. Guru_sample displaying under tables. Out of these 55 Tables, below … If Table1 is a partitioned table, then for basic statistics you have to specify partition specifications like above in the analyze statement. When executing describe (GET) on this table, original comments are lost and are replaced with "from deserializer" string. The path might include multiple components in the case of a nested type definition. 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. Let us look at the data storage in a single Hadoop Distributed File System. … materialized_view_name The name of the materialized view. @Guilherme Braccialli If you've already analyzed the columns you can issue a describe table command to get column stats: "As of Hive 0.10.0, the optional parameter FOR COLUMNS computes column statistics for all columns in the specified table (and for all partitions if the table is partitioned). Physically, each table is associated with a directory in HDFS. As per Hive 1.12, we have 55 Tables in Metastore DB (Mysql in my case). … In this post, we will check Apache Hive table statistics – Hive ANALYZE TABLE command and some examples. In the Below screenshot, we are creating a table with columns and altering the table name. 1. Rows with long column names do not align well with other columns. table_name: A table name, optionally qualified with a database name. The following query deletes all the columns from the employee table and replaces it with emp and name columns: hive> ALTER TABLE employee REPLACE COLUMNS ( eid INT empid Int, ename STRING name String); JDBC Program. The DESCRIBE statement in Hive shows the lists of columns for the specified table. DESCRIBE TABLE in Hive. What is the difference between describe table vs show create table? Create Table Syntax: CREATE TABLE [IF NOT EXISTS] [db_name. Examples. It creates a table with some comments on columns. The advantage of partitioning is that since the data is stored in slices, the query response time becomes faster. HIVE is considered a tool of choice for performing queries on large datasets, especially those … DESCRIBE EXTENDED and DESCRIBE FORMATTED. The table we create in any database will be stored in the sub-directory of that database. --Use hive format CREATE TABLE student (id INT, name STRING, age INT) STORED AS ORC; --Use data from another table CREATE TABLE student_copy STORED AS ORC AS SELECT * FROM student; --Specify table comment and properties CREATE TABLE student (id INT, name STRING, age INT) COMMENT 'this is a comment' STORED AS ORC TBLPROPERTIES ('foo'='bar'); --Specify table comment and properties … To set a table comment, run: ALTER TABLE table_name SET TBLPROPERTIES ('comment' = 'A table comment.') many databases such as MySQL, Hive provides DESCRIBE command that allows you to get the structure of a given table. ALTER TABLE hiveFirstTable ADD COLUMNS (col1_name String); Replace all the columns with new columns, this command will only work if datatypes of new and old columns will be compatible … Describe ways in which HIVEQL can be extended. Also, it's critical to know a default field delimiter if field delimiter setting is missed in a create statement. You can check the Course Preview of Big Data Hadoop and Spark Developer Certification course here! Syntax {DESC | DESCRIBE} [TABLE] [format] table_identifier [partition_spec] [col_name] Parameters. describe tablename:- provides column_name , column_type and comment information of the table. 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. Further, for populating the bucketed table with the temp_user table below is the HiveQL. ]table_name Like [db_name].existing_table [LOCATION hdfs_path] Create Table Statement: create table if not exists Employee.data like cloudduggudb.serde_example LOCATION … This chapter describes how to drop a table in Hive. See Column Statistics in Hive for details. When a field delimiter is not assigned properly, Hive can't split data into columns, and as a result, the first column will contain all data and the rest of columns will have NULL values. In CDH 5.5 / Impala 2.3 and higher, you can specify the name of a complex type column, which takes the form of a dotted path. You … To list out the databases in Hive … To add column b with int data type and column c with float data type use alter table x1 add columns (b int, c float); and press Enter now table x1 has two columns b and c. You can run describe table x1; to verify whether these columns have been added or not. Hive uses the statistics such as number of rows in tables or table partition to generate an optimal query plan. When you drop a table from Hive Metastore, it removes the table/column data and their metadata. Table Operations such as Creation, Altering, and Dropping tables in Hive can be observed in this tutorial. The CREATE TABLE statement follows SQL conventions, but Hive’s version offers significant extensions to support a wide range of flexibility where the data files for tables are stored, the formats used, etc. to gather column statistics of the table (Hive 0.10.0 and later). Description. There is nothing like SHOW VIEWS in Hive. I’ve a table zipcodes with column names RecordNumber, City, Zipcode and State. It provides a mechanism to project structure onto the data in Hadoop and to query that data using a SQL-like language called HiveQL (HQL). In the hive, we can use describe command to see table structure, its location as well as its table properties. Altering table "guru_sample" as … Introduces new DESCRIBE PRETTY table_name command and hive.cli.pretty.output.num.cols conf parameter. import java.sql.SQLException; import java.sql.Connection; import … Adding new column/columns to the existing tables. You can run describe table x1; to verify. Hence, we will create one temporary table in hive with all the columns in input file from that table we will copy into our target bucketed table for this. If EXTENDED is specified then additional metadata information (such as parent database, owner, and access time) is returned.. table_identifier [database_name.] Hence, if you wanted to restrict access to a column of sensitive data, the workaround would be to first create view for a subset of columns, and then grant privileges on that view. We can perform the various operations with these tables like Joins, … To convert columns to the desired type in a table, you can create a view over the table that does the CAST to the desired type. Displaying tables present in guru99 database. The Describe has following variation. Currently, DESCRIBE does not support tables created in a file system. … DESCRIBE SCHEMA. I ... You can also get the HDFS location of each partition by running any of the following Hive commands. Simple describe command will return only table columns and datatypes. The attached screenshot shows the following two problems: 1. Syntax DESCRIBE [EXTENDED | FORMATTED] [db_name. Get summary, details, and formatted information about the … As the name suggests, DESCRIBE is used to describe command to describe the structure of a table. Followings can be given with or without giving database information. DESCRIBE TABLE statement returns the basic metadata information of a table. delta.``: The location of an existing Delta table. The data type of column a is changed to float. Apache Hive is data warehouse infrastructure built on top of Apache™ Hadoop® for providing data summarization, ad hoc query, and analysis of large datasets. Set a table comment. ]materialized_view_name; db_name The database name. Even if you create a table with non-string column types using this SerDe, the DESCRIBE TABLE output would show string column type. 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). The default location where the database is stored on HDFS is /user/hive/warehouse. DESCRIBE FORMATTED zipcodes PARTITION(state='PR'); SHOW TABLE EXTENDED LIKE zipcodes PARTITION(state='PR'); Running SHOW TABLE EXTENDED on table and partition results in the below … To reduce the administrative overhead associated with such an approach, … Drop Table Statement. The DROP TABLE statement in Hive deletes the data for a particular table and remove all metadata associated with it from Hive metastore. ALTER VIEW works on … For example, if you are working in the dfs.myworkspace schema, you can issue the DESCRIBE command on a view or table in another schema, such hive or dfs.devworkspace. Use this handy cheat sheet (based on this original MySQL cheat sheet) to get going with Hive and Hadoop. Other than optimizer, hive uses mentioned statistics in many other ways. You can issue the DESCRIBE command on a table or view from any schema. In this Post, we will see what are the important Hive Metastore Tables that you may need to modify/query for different Hive Purposes that can not be achieved from Hive CLI or Beeline. These details are not required on regular basis but very useful when you do a Manual Migration of Hive Metadata. Redshift DESCRIBE Table Command Alternative. Syntax: DESCRIBE [EXTENDED|FORMATTED] [db_name.] If PURGE … The table data consists of all the data … Tables have some features such as partitioning regularly associated with higher-end data warehouse systems. Detail and description of the Hive tables. Moreover, let’s suppose we have created the temp_user temporary table. WHERE, ORDER BY, SORT BY and LIMIT clause can be used on views. 4. For whatever the column name we are defining the order by clause the query will selects and display results by ascending or descending order the particular column values. If our input column layout is according to the expected layout and we already have separate input files for … IF … Here is the output of these commands: If a table contains very long comments or very long column names, the output of DESCRIBE table_name is not aligned nicely. treats all columns to be of type String. The metadata information includes column name, column type and column comment. We discussed many of these options in Text File Encoding of Data Values and we’ll return to more advanced options later in Chapter 15.In this section, we describe the other options available for the CREATE … Previously, Sentry supported privilege granularity only down to a table. Let’s describe What is HiveQL SELECT Statement In addition, we need to set the property … Otherwise a semantic analyzer exception will be thrown. The partitioning in Hive … Logically, each table has a structure based on the definition of its columns, partitions and other table properties. Optionally a partition spec or column name may be specified to return the metadata pertaining to a partition or column respectively. The optional format of describe output. Parameters. As we know that Hadoop is used to handle the huge amount of data, it is always required to use the best approach to deal with it. Rows with long comments … partition_spec. The way of creating tables in the hive is very much similar to the way we create tables in SQL. In this mode, input data should contain the columns listed only in table definition (for example, firstname, lastname, address, city, post, phone1, phone2, email and web) but not the columns defined in partitioned by clause (country and state). Order by clause use columns on Hive tables for sorting particular column values mentioned with Order by. To get column names in a table we can fire: show columns in . To get description of a table (including column_name, column_type and many other details): describe [formatted] . I know that I can use the above query and filter the result to get the columns names and types. 2. EXTERNAL and LOCATION clause also works for views. This setting is requested for delimited text files placed as source of Hive tables. An optional parameter that specifies a … However for column statistics, if no partition specification is given in the analyze statement, statistics for all partitions are computed. In Apache Hive a new table can be created based on an existing table, in this process, the only table structure is created, table content is not copied. The table in the hive is consists of multiple columns and records. Describing Table. 3. ... Adding/replacing columns in Hive Table. You can get extensive formatted and unformatted information about a materialized view. CDH 5.5 introduces column-level access control for tables in Hive and Impala. Data Storage in a single Hadoop Distributed File System. 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. In CDH 5.7 / Impala 2.5 and higher, the DESCRIBE DATABASE form can display information … If the mentioned order by field is a string, then it will display the result in lexicographical order. 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. Define HIVE Query Language or HIVEQL. Creating table guru_sample with two column names such as "empid" and "empname" 2. If a specified property does not exist, an exception is thrown. Drop table or view properties. For example, consider below example of Hive describe command. You can issue the DESCRIBE SCHEMA command on any schema. ALTER (TABLE | VIEW) table_name UNSET TBLPROPERTIES [IF EXISTS] (key1, key2,...) Drop one or more properties of an existing table or view. DROP TABLE in Hive . format. table_name[.col_name ( [.field_name])]; DDL DESCRIBE TABLE Example: 4. Given below is the JDBC program to replace eid column with empid and ename column with name.