10+ BIM SERVICES. DDG Interview Questions and Answers

Tables are joined in SQL based on common columns, specified conditions, and join type.

• Common columns: Tables are joined based on columns that have the same values in both tables.

• Specified conditions: Join conditions are specified using the ON keyword in SQL.

• Join type: Different types of joins like INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN determine how the tables are joined.

Context management in Python is handled using the 'with' statement to ensure resources are properly managed and released.

• Use the 'with' statement to create a context manager

• Implement the __enter__() and __exit__() methods in a class to define the behavior of the context manager

• Resources like files, database connections, or locks can be managed using context managers

• Example: with open('file.txt', 'r') as file: # File operations here

File operations in Python involve opening, reading, writing, and closing files.

• Use the 'open()' function to open a file in different modes (read, write, append, etc.)

• Use 'read()' or 'readline()' to read content from a file

• Use 'write()' to write content to a file

• Remember to close the file using 'close()' to free up system resources

Common git commands include add, commit, push, pull, clone, and merge.

• git add : Add file changes to the staging area

• git commit -m 'message': Commit staged changes with a message

• git push: Push committed changes to a remote repository

• git pull: Fetch and merge changes from a remote repository

• git clone : Clone a repository from a remote location

• git merge : Merge changes from a different branch

The '==' operator compares the values of two objects, while the 'is' keyword checks if two objects are the same instance.

• Use '==' for value comparison, use 'is' for object identity comparison

• Example: x == y (compares values), x is y (checks if same instance)

• The '==' operator can be overloaded by classes, but 'is' cannot be overloaded

The init method in Python is a special method used to initialize objects of a class.

• The init method is called when a new object is created from a class.

• It is used to initialize the attributes of the object.

• The init method is defined with the __init__ keyword in Python.

• Example: class MyClass: def __init__(self, x): self.x = x obj = MyClass(5)

Types of joins in SQL include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.

• INNER JOIN: Returns rows when there is at least one match in both tables.

• LEFT JOIN: Returns all rows from the left table and the matched rows from the right table.

• RIGHT JOIN: Returns all rows from the right table and the matched rows from the left table.

• FULL JOIN: Returns rows when there is a match in one of the tables.

sudo stands for 'superuser do' and is a command in Unix/Linux systems that allows a permitted user to execute a command as the superuser or another user.

• sudo allows users to perform administrative tasks without logging in as the root user

• It is commonly used to run commands that require elevated privileges, such as installing software or modifying system files

• Example: sudo apt-get update

Indexing in SQL is a way to optimize the performance of queries by creating a data structure that allows for faster retrieval of data.

• Indexes are created on columns in a table to speed up the retrieval of rows based on certain conditions.

• Types of indexes include clustered, non-clustered, unique, and composite indexes.

• Examples of SQL indexing commands include CREATE INDEX, DROP INDEX, and ALTER INDEX.

Callback functions are functions that are passed as arguments to other functions and are executed after a certain task is completed.

• Callback functions are commonly used in asynchronous programming to handle tasks that take time to complete.

• They allow for more flexible and modular code by separating concerns.

• An example of a callback function is the setTimeout function in JavaScript, where a function is executed after a specified time interval.