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How Do SQL Commands Work

Reading time 2 min
Published Jan 3, 2016
Updated Oct 3, 2019

Web Development Course:

SQL commands are clear, declarative statements. SQL syntax is easy to understand, and managing data in SQL databases accurately and consistently is not a big challenge.

SQL commands are not case-sensitive, and that makes them even more convenient. Small errors like wrong capitalization won’t break your script. However, it’s a common practice to write the statements in all caps to ensure better readability. We will use this approach in our tutorials as well.

SQL Commands: Main Tips

  • To interact with SQL databases, you need to use SQL commands (also called SQL statements).
  • Databases are tables that consist of columns (they represent attributes of an entry) and rows (they represent individual data entries).
  • SQL is not case-sensitive, but writing SQL commands in ALL CAPS improves readability of your code.
  • Certain databases may require a semicolon (;) after each statement. Usually this rule applies when you need to enter a few statements in a single call to the server.

SQL Statement Syntax Example

Let's try performing one of the most common actions in SQL – selecting certain data.

For our example, we are using a demo database, and we want to get all the records from the Customers table.

The following SQL command is all you need for this task.

Example
SELECT * FROM Customers;

Note: The asterisk (*) is an operator to select all the entries from the specified table.

SQL Syntax Cheet Sheet

  • SELECT – selects data from the database.
  • DELETE – removes data from the database.
  • UPDATE – overwrites data in the database.
  • CREATE DATABASE – creates a new database.
  • INSERT INTO – uploads new data into the database.
  • CREATE TABLE – creates a new table.
  • ALTER DATABASE – changes the attributes, files or filegroups of the database.
  • CREATE INDEX – creates an index, or a search key.
  • DROP INDEX – deletes an index.
  • ALTER TABLE – changes the attributes or entries of a table.

SQL Commands: Summary

  • SQL commands, or SQL statements, are used to interact with SQL databases.
  • Databases consist of columns (attributes of entries) and rows (individual data entries).
  • Usually SQL commands are written in all caps for better readability, but SQL is not case-sensitive and all capitalization options work equally.
  • You may need to use a semicolon (;) after each statement for some databases.