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SQL Basics

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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 a sentence or a 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.

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    To recap, SQL or Structured Query Language 0:00
    is a specialized language to get information or data out of a database. 0:04
    There are many different database systems such as MySQL, 0:09
    Microsoft SQL Server, Oracle, PostgreSQL, and SQLite. 0:13
    All of them use the same language, SQL. 0:18
    Just like spoken languages, programming languages have their own vocabulary and 0:21
    grammatical structure. 0:25
    Programmers refer to this vocabulary and grammar as syntax. 0:27
    Thankfully, most programming languages have a much smaller vocabulary 0:30
    than spoken languages. 0:34
    Though they are few, 0:36
    the vocabulary words in programming languages are very important. 0:37
    And we call them key words. 0:41
    [SOUND] A keyword is a command that you issue to a computer to do a certain thing. 0:42
    And SQL has its own sets of keywords. 0:48
    Lines of SQL code are known as a Statement or a Query. 0:51
    A statement in SQL is like a sentence in English. 0:56
    A query in SQL is like asking a question in English. 0:59
    Most queries, no matter how complex, are issued to the database one at a time. 1:03
    You may hear the issuing of a statement being referred to as running a query, or 1:09
    executing the SQL. 1:14
    Let's take a look at a common SQL query. 1:16
    We'll retrieve all information from the table with the data about books. 1:19
    Remember, a table is one of the spreadsheet like structures 1:24
    inside a database made up of rows and columns. 1:27
    Let's see how we might write a query in English first. 1:31
    [SOUND] What is all the information we have about each book in the books table? 1:36
    Now, let's see the SQL syntax to bring back all the information from 1:41
    the books table. 1:44
    See those upper case words there, SELECT and FROM? 1:45
    They are key words or special words reserved for the SQL programming language. 1:48
    You issue a select command when you want to write a query. 1:54
    You're asking the database to select or 1:58
    retrieve some of the information from a particular table. 2:00
    In this case, it's books. 2:04
    The asterisk, or the star character, means you want to bring 2:06
    all of the information in all of the tables' columns back. 2:09
    I'll show you how to bring back specific columns of information later. 2:13
    The semicolon at the end of the query is like a period or 2:17
    a question mark at the end of a sentence or question. 2:21
    The semicolon lets the database know where the statement ends or terminates. 2:24
    When we issue the statement to the database, 2:29
    you can expect all entries in the books table to be returned. 2:31
    Let's see the results of this query in the SQL playground and 2:35
    see this query in action. 2:39
    As you can see, it brings back all information in the books table. 2:42
    Let's ask another question. 2:46
    Who are all the users of the library in the patrons table? 2:48
    We'd use the SELECT keyword, 2:52
    star, meaning all of the columns, 2:55
    FROM, and then the table name. 2:58
    In this case, the table name is patrons. 3:00
    Don't forget the semicolon to terminate the statement. 3:04
    Once we execute this query, it will return all patron information. 3:07
    So generally speaking, writing SELECT * FROM &lt;table name&gt;; 3:12
    is a query we can use to retrieve all data from any table. 3:17
    This can be useful for small data sets. 3:22
    When you have larger data sets like the users of a large social network, or 3:25
    the orders from a popular e-commerce site, you probably don't want to run queries 3:30
    like this because it can take a very long time to execute and return the results. 3:35
    This can slow the performance down for other database users too. 3:40
    However, the data sets in this course are very small, and 3:44
    running these types of queries won't have any real performance impact. 3:48
    Databases have more utility than reporting all the information in one table. 3:52
    In the next video, I'll show you how to bring back specific columns. 3:57

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