Top Essential SQL Commands and Functions

SQL (Structured Query Language) is the standard language used for accessing, managing, and manipulating databases. While SQL follows the ANSI/ISO standard, each database system (like MySQL, PostgreSQL, or SQL Server) may have slight variations. Still, they all share the same fundamental commands and structure.

Table Management Commands​

• CREATE TABLE → Creates a new table in the database.
• ALTER TABLE → Adds new columns or modifies existing ones.

Data Retrieval Commands​

• SELECT → Fetches data from one or more tables.
• SELECT DISTINCT → Returns only unique values.
• WHERE → Filters rows that meet specific conditions.
• BETWEEN → Retrieves results within a specific range.
• LIKE → Searches for a pattern within a column.
• LIMIT → Restricts the number of rows in the result set.
• ORDER BY → Sorts results alphabetically or numerically.

Table Relationship Commands​

• INNER JOIN → Combines rows from multiple tables when the join condition is true.
• OUTER JOIN → Combines rows even if the join condition is not met.

Aggregate and Group Functions​

• SUM() → Returns the total sum of a numeric column.
• AVG() → Calculates the average of a column.
• MIN() / MAX() → Returns the smallest or largest value.
• COUNT() → Counts the number of non-null rows.
• ROUND() → Rounds numbers to a specific decimal place.
• GROUP BY → Groups rows with identical values.
• HAVING → Filters results after grouping (used with GROUP BY).

Data Manipulation Commands​

• INSERT → Adds new records to a table.
• UPDATE → Modifies existing records in a table.
• DELETE → Removes specific records from a table.

Logical and Conditional Operators​

• IS NULL / IS NOT NULL → Checks for empty values.
• AND / OR → Combines multiple conditions.
• AS → Renames a column or table using an alias.
• CASE → Creates conditional output within queries.
• WITH → Stores a query result temporarily using an alias.

Why SQL Is So Important​

SQL is the backbone of data-driven applications - from websites and business analytics to mobile apps and financial systems.
Knowing these core commands helps you:
Write clean and efficient queries.
Manage and analyze large datasets easily.
Build and optimize databases for better performance.

Pro Tip: Practice SQL with real data using platforms like SQLite, MySQL Workbench, or pgAdmin - and you’ll see your skills grow fast!