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Master SQL, PostgreSQL, MySQL, MongoDB, and trending open-source databases. Learn optimization, design patterns, and best practices for modern data management.

323 articles
1 min read

SQL DROP TABLE

DROP TABLE is used to delete a table permanently from the database along with all its data. Use it carefully! 🔹 Basic Syntax 🔹…

2 min read

SQL ALTER TABLE (Add, Drop, Modify)

ALTER TABLE lets you change an existing table’s structure — add, drop, or modify columns and constraints without losing data. 🔹 Basic Syntax 🔹…

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SQL CREATE TABLE

Creating tables is fundamental — tables store your data in rows and columns. 🔹 Basic Syntax 🔹 Example Creates an employees table with 5…

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SQL DROP DATABASE

DROP DATABASE is used to delete an existing database permanently along with all its tables, data, and objects. Use it with care! 🔹 Basic…

1 min read

SQL CREATE DATABASE

Creating a database is the first step to start storing your data. The CREATE DATABASE command creates a new, empty database in your SQL…

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SQL Window Functions

Window functions let you perform calculations across rows related to the current row, without collapsing the result like GROUP BY does. They’re great for…

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SQL SELECT INTO

SELECT INTO lets you create a new table and insert data from an existing query — all in one step.It’s handy for quick backups,…

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SQL EXISTS / ANY / ALL

These keywords are used with subqueries to perform advanced comparisons.Let’s break them down simply: 🔹 EXISTS – Check if Subquery Returns Rows Returns TRUE…

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SQL Subqueries

A subquery is a query inside another query. It’s used to fetch intermediate results for comparison, filtering, or transformation. Types of subqueries: 🔹 Scalar…

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SQL Aliases

Aliases are temporary names you assign to columns or tables to make query results cleaner or easier to read. They are especially useful in:…

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SQL UNION / UNION ALL

UNION and UNION ALL combine results from two or more SELECT queries.Both must have the same number of columns with compatible data types. 🔹…

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SQL CROSS JOIN

A CROSS JOIN returns every possible combination of rows from two tables.It’s called a Cartesian product – no ON clause is required. 🔹 Basic…