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SELECT Statement

SELECT is like asking a librarian to bring you certain columns from a table. It is the most common way to look at what is stored.

In this page:

  1. Introduction to SELECT
  2. Selecting Specific Columns
  3. Basic Math in SELECT
  4. System Information Queries
  5. Best Practices for SELECT
Syntax
sql 
SELECT column1, column2 FROM table_name;

SELECT * FROM table_name;

Introduction to SELECT

SELECT retrieves rows from a table and is the single most frequently used SQL statement, forming the foundation of nearly every read operation an application performs against its database.

Example: Introduction to SELECT

sql 
SELECT * FROM users;

Selecting Specific Columns

Naming specific columns instead of retrieving every column reduces the amount of data MySQL has to read and transmit, which measurably speeds up queries on wide tables or over slow network links.

Example: Selecting Specific Columns

sql 
SELECT name, email FROM users;

Basic Math in SELECT

You can perform arithmetic directly inside a SELECT's column list — like multiplying price by quantity — to compute derived values on the fly without altering anything stored in the table.

Example: Basic Math in SELECT

sql 
SELECT name, price * quantity AS total FROM orders;

System Information Queries

SELECT can also return values with no table involved at all, such as the server's current time or version, which is a handy way to sanity-check a connection is alive.

Example: System Information Queries

sql 
SELECT VERSION();

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Best Practices for SELECT

Avoiding SELECT * in production code is a widely recommended practice: fetching only the columns you actually need avoids wasted memory, network traffic, and breakage if the table's columns change later.

Example: Best Practices for SELECT

sql 
-- Avoid SELECT * in production; name only the columns you need
SELECT name, email FROM users;
Related Topics

SELECT DISTINCT · SELECT with Aliases · INSERT INTO SELECT · UPDATE Statement

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Common Mistakes
  1. Using SELECT * on large tables when only a few columns are needed, which transfers unnecessary data.
  2. Misspelling a column name, which gives an Unknown column error.
  3. Expecting rows in a specific order without ORDER BY.
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