Database and SQL for Beginners

Define a database as a unified collection of data used to store and retrieve related information, with SQL as the language clients use to interact with a DBMS.

Explore DBMS features like data integrity, constraints, security, data sharing, and concurrency, plus backup, replication, high availability, and auditing to keep data reliable, secure, and always available.

Identify entities, attributes, and relationships in data, using examples like student, course, exam, account, and transaction, and see how the entity relationship diagram maps one account to many transactions.

Explore the relational model as the dominant data storage approach, using SQL to interact with relational DBMS, and contrast it with NoSQL systems like MongoDB and Dynamo DB.

Learn SQL, the structured query language for relational databases, standardized by ANSI, with a focus on data definition and data manipulation and on retrieving data.

Master the select command to retrieve data from tables, perform projection by choosing specific columns, use expressions and column aliases for meaningful headings, and apply distinct to return unique values.

Master selection in SQL by querying the employees table with where clauses to retrieve specific rows. Use relational and logical operators to filter by id, salary, and department.

Learn how to use SQL operators such as between, in, is null, and like to filter salaries, job ids, and department names, using readable patterns with percent and underscore wildcards.

Explore how string comparison behaves in different databases, explaining case sensitivity versus case insensitivity, how like operators differ, and why SQL Server is case sensitive while others may not.

Sort employee data with the order by clause, choosing ascending or descending order, possibly on multiple columns such as department id and salary, without modifying the original data.

Learn to use begin transaction, commit, and rollback to group related changes into a single unit, preventing data inconsistency across balance and transaction tables.

Explore numeric functions in databases, including abs (absolute value), round with decimal precision, random numbers, and a sign-like function; test with simple selects and note cross‑db variations.

Explore date time functions to get current date and time in UTC or local time, format dates, extract year or month, and compute the difference in days via Julian day.

Explore miscellaneous sql functions, including ifnull, immediate if, nullif, and koalas, along with cast and typecasting and tracking rows affected by previous dml commands.

Learn to use the having clause to filter groups after aggregation, using group by, where, and order by to identify departments or employees that meet specific thresholds.

Learn how to use join clauses to connect employee records with their corresponding job titles, avoid the Cartesian product, and use aliases like E and J for concise queries.

Join employees and departments to display employee name, salary, and department name, with aliases, and filter by salary above eight lakhs while understanding normalization.

Learn to disambiguate column references by qualifying with table names in SQL, avoid ambiguous column errors, and use aliases to clarify results across databases.

Learn to join three or more tables to display rich data, such as employer id, full name, salary, job title, and department name, by linking employees, departments, and jobs.

Understand outer joins in SQL, including left outer join, inner join, and on clause usage, to display job titles with employee names and include unmatched jobs.

Master subqueries to identify departments with employees earning more than five lacs, use in and not in for department filtering, and check current-year joins by year comparisons.

Use subqueries and aggregates to filter by average salary, join employees and departments, and handle ambiguous column names while identifying employees who have not taken any leave.

Explore multiple and nested subqueries that feed the main query to filter employees by job titles and departments starting with a.

Explore top-n analysis in sql by using limit and offset to fetch top salaries and top departments by average salary, and use subqueries to combine results.