Database Engineer/DBA – (MySQL, MongoDB, SQLite)

The MySQL is the world’s most popular open source database.This course will teach you  a lot to  start using this incredibly popular MySQL database and gain useful skills in the process.  In learning about MySQL you will also gain an understanding of relational databases in general.  Furthermore, you will harness that power by learning SQL and using it to build databases, populate them with data and query that data through extensive hands–on practices.

MongoDB is a document–oriented DBMS, with JSON–like  objects comprising the data model, rather  than RDBMS tables. MongoDB does not support joins nor transactions. However, it features  secondary indexes, an expressive query language,atomic writes on a per–document level, and fully–consistent reads. MongoDB uses JSON, a binary object format similar to, but more expressive than JSON.
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MongoDB uses dynamic schema. We can create collections without defining the structure,i.e. the fields or the types of their values, of the documents. You can change the structure of documents simply by adding new fields or deleting existing ones. Documents in a collection need unique set of fields.

MongoDB database stores its data in collections  not in tables The collections are the rough equivalent of RDBMS tables. 
A collection holds one or more documents, which corresponds to a record or a row in a relational database table, and each document  has one or more fields, which corresponds  to a column in a relational database table.