CODEWITHSUNDEEP
apache-drill
Sanjiv
Sanjiv

Reputation: 1288

How to Select all the column name from file (e.g:- csv or, json or, parquet) in Apache Drill

I am using Drill in Window 10 in embedded mode having latest version 1.8.

I have a Drill query for selecting all the columns from a sql server database table:-

SELECT DISTINCT info.COLUMN_NAME AS `NAME`, info.TABLE_SCHEMA AS `TABLESCHEMA`, info.TABLE_NAME AS `TABLENAME`, info.ORDINAL_POSITION AS `POSITION`, info.IS_NULLABLE AS `ISNULLABLE`, info.DATA_TYPE AS `DATATYPE`, tc.CONSTRAINT_TYPE AS `CONSTRAINTTYPE`, kcufk.TABLE_SCHEMA AS `REFRENCESCHEMA`, kcufk.TABLE_NAME AS `REFRENCETABLE`, kcufk.COLUMN_NAME AS `REFRENCECOLUMN` FROM DemoSQLServer.INFORMATION_SCHEMA.`COLUMNS` info LEFT OUTER JOIN DemoSQLServer.INFORMATION_SCHEMA.`KEY_COLUMN_USAGE` kcu ON kcu.COLUMN_NAME = info.COLUMN_NAME AND kcu.TABLE_NAME = info.TABLE_NAME LEFT OUTER JOIN DemoSQLServer.INFORMATION_SCHEMA.`TABLE_CONSTRAINTS` tc ON tc.CONSTRAINT_NAME = kcu.CONSTRAINT_NAME AND tc.TABLE_NAME = kcu.TABLE_NAME LEFT OUTER JOIN DemoSQLServer.INFORMATION_SCHEMA.`REFERENTIAL_CONSTRAINTS` rk ON rk.CONSTRAINT_NAME = tc.CONSTRAINT_NAME LEFT OUTER JOIN DemoSQLServer.INFORMATION_SCHEMA.`KEY_COLUMN_USAGE` kcufk ON kcufk.CONSTRAINT_NAME = rk.UNIQUE_CONSTRAINT_NAME WHERE info.TABLE_NAME = 'Attribute' AND info.TABLE_SCHEMA = 'dbo' ORDER BY info.ORDINAL_POSITION ASC;

This query will return all the columns from the attribute table.

I want to select column name from some files(e.g:-csv or, parquet or, json,etc). Is it possible using Drill.?

Upvotes: 0

Views: 777

Answers (1)

Dev
Dev

Reputation: 13753

You can select columns for files in a similar way like tables.

Sample query: 

select N_NAME,N_REGIONKEY from dfs.`<drill-home>/sample-data/nation.parquet`;

P.S. - Make sure dfs plugin is enabled.

Upvotes: 2

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