SQL Reference Guide

Revision Time: 2 mins

1. SQL Syntax Reference

Basic SQL syntax everyone should know.

SELECT

Return: Table

Query data from columns.

Syntax signature:SELECT column1, column2 FROM table;

Code snippet:

python

SELECT name, age FROM users;

Expected Output:Selected fields from users.

Remember: Always ensure correct syntax formatting when calling SELECT.

FROM

Return: Value

Specify target table.

Syntax signature:SELECT * FROM table;

Code snippet:

python

SELECT * FROM orders;

Expected Output:All records from orders.

Remember: Always ensure correct syntax formatting when calling FROM.

WHERE

Return: Value

Filter row records based on condition.

Syntax signature:SELECT * FROM table WHERE condition;

Code snippet:

python

SELECT * FROM users WHERE status = 'Active';

Expected Output:Active users only.

Remember: Always ensure correct syntax formatting when calling WHERE.

DISTINCT

Return: Value

Eliminate duplicate rows.

Syntax signature:SELECT DISTINCT column FROM table;

Code snippet:

python

SELECT DISTINCT department FROM employees;

Expected Output:Unique departments list.

Remember: Always ensure correct syntax formatting when calling DISTINCT.

ORDER BY

Return: Value

Sort rows ascending or descending.

Syntax signature:SELECT * FROM table ORDER BY column [ASC|DESC];

Code snippet:

python

SELECT * FROM employees ORDER BY salary DESC;

Expected Output:Sorted list of employees.

Remember: Always ensure correct syntax formatting when calling ORDER BY.

LIMIT / TOP

Return: Value

Constrain returned row count.

Syntax signature:SELECT * FROM table LIMIT count;

Code snippet:

python

SELECT * FROM logs ORDER BY timestamp DESC LIMIT 5;

Expected Output:Top 5 latest logs.

Remember: Always ensure correct syntax formatting when calling LIMIT / TOP.

Aliases (AS)

Return: Value

Rename columns or tables temporarily.

Syntax signature:SELECT column AS alias_name FROM table;

Code snippet:

python

SELECT total_amount AS order_total FROM orders;

Expected Output:Columns renamed in output.

Remember: Always ensure correct syntax formatting when calling Aliases (AS).

Next Topic2. Filtering Data