Learn Big Data With Me - Hive

Introduction

• Structured data like database tables.
• Unstructured data like videos, audios, PDF, TXT files, etc.
• Semi-structured data like XML.

• In SQL, we can insert the data values row by row but not in HQL.
• In SQL we can update any row or column but not in HQL because the data is stored in HDFS, after putting data into HDFS, you shouldn’t change the contents of the data.
• In SQL, we can use delete but not in HQL.

1. Managed tables or Internal tables.
2. External tables.

• String can contain any kind of data.
• In SQL, if you want to insert the data, you have to first create schema or table but in HQL, you can either create the table and insert the data or you can insert the data and then create the table.
• If you apply it after the table column in create a statement in HQL, it will give you null but not actual data and it will not give you an error, so you need to write delimiter & terminated line.

• If it is a local file system, the default path is home/user.
• If it is HDFS, it is a user.

• If we are creating internal tables, the table name is created as a directory on the warehouse. If we are creating the external tables, the table name will never be created as a directory name but is just trying to refresh some location /vimal/newfolder.
• For global usage, you can refer to an external table but not an internal table.