In our previous lesson, we tackled the foundational knowledge of the logical operators AND/OR in SQL. Now, we're going to extend this knowledge by introducing SQL conditional operators, which will further enhance the precision and detail of your queries. These operators include LIKE, BETWEEN, and IN.
In essence, conditional operators in SQL allow us to filter the output of our SQL queries based on certain criteria or conditions. They're used in conjunction with the SQL WHERE clause to specify the conditions that data must meet to be included in the query results. Let's delve into each of these conditional operators.
The LIKE operator in SQL is used in a WHERE clause to search for a specified pattern within a column. More often than not, it works with wildcard characters, such as the percentage % sign, which can represent zero, one, or multiple characters.
Here's an example showing how the LIKE operator is used:
SQL1-- Use LIKE operator to find all albums released in the 2000s 2SELECT AlbumName, ReleaseDate 3FROM Albums 4WHERE ReleaseDate LIKE '200%';
In the above example, we search for all albums in the Albums table whose ReleaseDate starts with '200', using the LIKE operator and the % wildcard. This will return all albums released from the year 2000 onwards.
The BETWEEN operator in SQL is used to select values within a specific range. These values can be numbers, text, or dates. It is used with the WHERE clause.
The syntax for using BETWEEN is column_name BETWEEN value1 AND value2, where value1 and value2 define the range within which to search.
Here's an example of a SQL query that uses the BETWEEN operator:
SQL1-- Use BETWEEN operator to choose songs of a certain duration 2SELECT Name, DurationMS 3FROM Songs 4WHERE DurationMS BETWEEN 200000 AND 300000;
In this query, the BETWEEN operator is used to filter songs from the Songs table whose DurationMS falls between 200000 and 300000.
The IN operator in SQL allows us to filter data based on multiple values in a WHERE clause. It serves as a shorthand for multiple OR conditions and it's often used when there's a need to compare a column with more than two values.
Consider this example of a SQL query using the IN operator:
SQL1-- Find songs from specific albums by Taylor Swift and list their album names
2SELECT
3 s.Name AS SongName,
4 a.AlbumName
5FROM Songs s -- 's' is an alias for the Songs table
6JOIN Albums a ON s.AlbumID = a.AlbumID -- 'a' is an alias for the Albums table
7WHERE a.AlbumName IN ('Folklore', 'Evermore', 'Lover');In this example, the IN operator permits us to select songs whose album names are 'Folklore', 'Evermore', or 'Lover'. The table aliases s and a are used to make the query concise — s represents the Songs table and a represents the Albums table. This helps in writing shorter and more readable SQL queries.
Great work so far, and congratulations! By reaching this point, you've developed a solid understanding of SQL conditional operators. Remember, these are powerful tools — when used correctly, they can make your data querying more detailed and precise.
Next up, you're going to get some hands-on practice. Applying the new skills you've acquired in different scenarios will reinforce your understanding and enhance your SQL proficiency. Look forward to applying these conditional operators in multiple contexts. You're doing great so far, and I'm confident that you'll effectively tackle the next section. Let's move on to the practice component and keep the SQL learning momentum going strong!