Select and From in PostgreSQL

2026-06-02 · Source: Alex The Analyst · Field: Technology & Digital — Data Science & Analytics, Software Development & Engineering · Depth: Novice, medium

Summary

This lesson introduces the fundamental `SELECT` and `FROM` statements in PostgreSQL, crucial for querying data. It explains how to retrieve all columns using `SELECT *` and specify the source table with `FROM table_name`, demonstrating with `character_info` and `ships` tables. The content also details selecting specific columns by listing them, handling multiple queries in a single editor using semicolons, and performing calculations directly within the `SELECT` statement. Furthermore, it covers aliasing columns with the `AS` keyword to rename calculated or existing columns, such as `estimated_net_worth * 2 AS double_the_worth`, improving readability and output clarity.

Key takeaway

For new Data Analysts or Software Engineers learning PostgreSQL, mastering `SELECT` and `FROM` is essential for foundational data retrieval. You should consistently use `SELECT` to specify desired columns (or `*` for all) and `FROM` to identify the target table. Remember to separate multiple queries with semicolons and utilize `AS` for clear column aliasing, especially when performing calculations, to ensure your query outputs are readable and maintainable.

Key insights

The `SELECT` and `FROM` statements are foundational for all PostgreSQL data querying, enabling column and table specification.

Principles

• SQL commands are conventionally uppercase.
• Semicolons separate multiple queries.
• Alias columns for clarity.

Method

To query data, use `SELECT` to specify columns (or `*` for all) and `FROM` to name the source table. Separate multiple queries with semicolons.

In practice

• Retrieve all data with `SELECT * FROM table_name;`.
• Calculate new values: `SELECT column_A * 2 AS new_column;`.
• Rename output columns using `AS alias_name`.

Topics

• PostgreSQL
• SQL Queries
• SELECT Statement
• FROM Statement
• Column Aliasing
• Database Fundamentals

Best for: Data Analyst, Software Engineer

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Editorial summary, takeaway, and curation by AIssential. Original article published by Alex The Analyst.