SQL Date & Time Functions
SQL provides powerful functions to handle dates and times — essential for filtering, formatting, and calculating time-based data. 🔹 Common Date Functions (DBMS-Agnostic Examples)…
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Database
Master SQL, PostgreSQL, MySQL, MongoDB, and trending open-source databases. Learn optimization, design patterns, and best practices for modern data management.
323 articles
SQL NULL Handling
In SQL, NULL represents a missing, undefined, or unknown value — it’s not the same as an empty string or zero. Understanding how to…
SQL GRANT / REVOKE (Permissions)
The GRANT and REVOKE statements are used to manage user access and privileges in SQL. These ensure users have only the permissions they need…
SQL Injection (Prevention Tips)
SQL Injection is a serious security vulnerability that allows attackers to execute malicious SQL code through user input. It can lead to data theft,…
SQL VIEW
A VIEW is a virtual table based on the result of a SQL query. It doesn’t store data itself, but shows data dynamically from…
SQL INDEX
An INDEX improves the speed of data retrieval on large tables by allowing the database to quickly locate rows. It’s like a book’s table…
SQL AUTO_INCREMENT / IDENTITY
To auto-generate unique values (usually for primary keys), databases offer built-in features like AUTO_INCREMENT (MySQL), IDENTITY (SQL Server), and GENERATED AS IDENTITY (PostgreSQL, Oracle).…
SQL CHECK
The CHECK constraint ensures that the values in a column meet a specific condition before being inserted or updated. It’s used to enforce domain-level…
SQL FOREIGN KEY
A FOREIGN KEY creates a link between two tables by enforcing a relationship. It ensures the value in one table matches a value in…
SQL PRIMARY KEY
The PRIMARY KEY uniquely identifies each row in a table. It ensures no duplicate or NULL values exist in the key column(s). 🔹 Basic…
SQL UNIQUE
The UNIQUE constraint ensures all values in a column (or group of columns) are distinct — no duplicates allowed. 🔹 Basic Syntax 🔹 Example…
SQL NOT NULL / DEFAULT
NOT NULL ensures a column must have a value — it cannot be left empty (NULL).DEFAULT sets a value automatically if no explicit value…