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Your First SQL Statement

4:01 with Andrew Chalkley

In this video you'll learn how to write your first SQL query: retrieving all information from one table.

Definitions

Syntax The vocabulary and grammatical rules surrounding the structure of your code.

Keywords The vocabulary words of a programming language used to issue commands to a computer.

SQL Used

SELECT * FROM <table name>;

The asterisk or star symbol (*) means all columns.

The semi-colon (;) terminates the statement like a period in sentence or question mark in a question.

Examples:

SELECT * FROM books;
SELECT * FROM products;
SELECT * FROM users;
SELECT * FROM countries;

See all of the SQL used in SQL Basics in the SQL Basics Cheat Sheet.

  • 0:00

    To recap, SQL or Structured Query Language

  • 0:04

    is a specialized language to get information or data out of a database.

  • 0:09

    There are many different database systems such as MySQL,

  • 0:13

    Microsoft SQL Server, Oracle, PostgreSQL, and SQLite.

  • 0:18

    All of them use the same language, SQL.

  • 0:21

    Just like spoken languages, programming languages have their own vocabulary and

  • 0:25

    grammatical structure.

  • 0:27

    Programmers refer to this vocabulary and grammar as syntax.

  • 0:30

    Thankfully, most programming languages have a much smaller vocabulary

  • 0:34

    than spoken languages.

  • 0:36

    Though they are few,

  • 0:37

    the vocabulary words in programming languages are very important.

  • 0:41

    And we call them key words.

  • 0:42

    [SOUND] A keyword is a command that you issue to a computer to do a certain thing.

  • 0:48

    And SQL has its own sets of keywords.

  • 0:51

    Lines of SQL code unknown as a Statement or a Query.

  • 0:56

    A statement in SQL is like a sentence in English.

  • 0:59

    A query in SQL is like asking a question in English.

  • 1:03

    Most queries, no matter how complex, are issued to the database one at a time.

  • 1:09

    You may hear the issuing of a statement being referred to as running a query, or

  • 1:14

    executing the SQL.

  • 1:16

    Let's take a look at a common SQL query.

  • 1:19

    We will treat all information from the table with the data about books.

  • 1:24

    Remember, a table is one of the spreadsheet like structures

  • 1:27

    inside a database made up of rows and columns.

  • 1:31

    Let's see how we might write a query in English first.

  • 1:36

    [SOUND] What is all the information we have about each book in the books table?

  • 1:41

    Now, let's see the SQL syntax to bring back all the information from

  • 1:44

    the books table.

  • 1:45

    See there's upper case words there, select and from.

  • 1:48

    They are key words or special words reserved for the SQL programming language.

  • 1:54

    You issue a select command when you want to write a query.

  • 1:58

    You're asking the database to select or

  • 2:00

    retrieve some of the information from a particular table.

  • 2:04

    In this case, it's books.

  • 2:06

    The asterisk, or the star character, means you want to bring

  • 2:09

    all of the information in all of the tables, columns back.

  • 2:13

    I'll show you how to bring back specific columns of information later.

  • 2:17

    The semicolon at the end of the query is like a period or

  • 2:21

    a question mark at the end of a sentence or question.

  • 2:24

    The semicolon lets the database know where the statement ends or terminates.

  • 2:29

    When we issue the statement to the database,

  • 2:31

    you can expect all entries in the books table to be returned.

  • 2:35

    Let's see the results of this query in the SQL playground and

  • 2:39

    see this query in action.

  • 2:42

    As you can see, it brings back all information in the books table.

  • 2:46

    Let's ask another question.

  • 2:48

    Who are all the users of the library in the patrons table?

  • 2:52

    We'd use the SELECT keyword.

  • 2:55

    Stop, meaning all of the columns.

  • 2:58

    From, and then the table name.

  • 3:00

    In this case, the table name is patrons.

  • 3:04

    Don't forget the semicolon to terminate the statement.

  • 3:07

    Once we execute this query, it will return all patron information.

  • 3:12

    So generally speaking, writing SELECT * FROM <table name>

  • 3:17

    is a query we can use to retrieve all data from any table.

  • 3:22

    This can be useful for small data sets.

  • 3:25

    When you have larger data sets like the users of a large social network, or

  • 3:30

    the orders from a popular e-commerce site, you probably don't want to run queries

  • 3:35

    like this because it can take a very long time to execute and return the results.

  • 3:40

    This can slow the performance down for other database users too.

  • 3:44

    However, the data sets in this course are very small, and

  • 3:48

    running these types of queries were having a real performance impact.

  • 3:52

    Databases have more utility than reporting all the information in one table.

  • 3:57

    In the next video, I'll show you how to bring back specific columns.

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