An important part of working within the world of data science is understanding when and how to use specific programming languages, technological tools, and/or software. Whether you are interested in data cleaning or creating machine learning models, there is always a set of skills required to truly master the best uses of each data science tool. For students and data science professionals that are knowledgeable of SQL, there are a variety of skills that this programming language brings to the table. The following list includes some of the most essential SQL skills for data science.
Data Organization and Database Design
Structured Query Language, or SQL, is a programming language that can be used when working with relational databases. An essential skill to learn and understand when working with SQL is how to use this language for data organization or database design (organizing data in such a way that discrete and/or relational categories are created). A stage that comes after the initial collection of data, data organization focuses on the creation of metadata. Metadata can be described as “data about data” and acts as a way to categorize different types of data or aspects of a dataset within a database. For example, if a data science professional was collecting data about the weather, some metadata categories that could be generated include the temperature, time of day, and the date that the weather was recorded.
Once metadata has been created, that information can then be used to identify specific data types. When using SQL, the Metadata Functions can be used to create objects as well as to name the different categories and types of data. When categorizing the weather data, some of the data might be numerical or integer data (such as the metadata category temperature) whereas other metadata might be letters or character-based, such as data about the geographic location of the weather or a qualitative coding of weather such as sunny or cloudy.
Metadata makes it significantly easier to begin to see the relationship between different aspects of a database, or what are known as data types within SQL. Creating these relationships is also completed by organizing the data into tables, which is another essential skill and function of using SQL for database design. By creating and naming tables, data science professionals are able to organize their datasets based on data types. Returning to the weather example, a data science professional might create a table that not only includes data types for characters, but also a data type for when the weather was recorded. By creating a join condition you can also see the relationships between multiple tables.
Querying and Search Functions
Another essential skill to learn when working with SQL is how to write queries and how to search the database for information that you need. As the name would imply, querying is the process of asking questions or making requests of a dataset or database. In this sense, querying can be understood as a form of data mining, and within the SQL programming language, querying can be used to uncover information within a database. By making inquiries or queries in a database, data science professionals can discover important information about whether or not data is missing from a dataset or unexpected findings about what patterns or trends reside within the dataset.
For instance, writing a query about the weather database might include commands focused on retrieving data about temperature. In retrieving this data, you would then be able to learn more about the trends or patterns in the weather for that dataset as it relates to the condition of temperature.
An essential skill to learn when writing queries in SQL is understanding the order of operations. The primary order of operations for SQL are SELECT, FROM, WHERE, ORDER BY, HAVING, and GROUP BY.
- SELECT is data you are selecting to receive.
- FROM selects data from a particular table.
- WHERE filters and retrieves data by a particular condition.
- ORDER BY arranges the data.
- GROUP BY arranges data into identical groups.
- HAVING clause is then used to filter data when writing queries.
As an essential skill in learning and utilizing SQL, remembering the order of operations will make it significantly easier for you to quickly write queries.
Relational Database Management Systems
As an open-source programming language, SQL is compatible with multiple languages and platforms, but it is primarily known for its uses with relational databases. Another essential skill that you need to learn when using SQL for querying is how to use SQL within specific relational database management systems. Relational database management systems (RDBMS) are programs that allow you to work within a database, and there are several of these systems that are compatible with the SQL programming language. Some of the most popular RDBMS that are used with SQL are MySQL, SQLite, SQL Server, and PostgreSQL.
For many data science professionals, MySQL is the go-to SQL database, because it is open-source, web-based, and easy to use. SQLite is another open-source database platform that is commonly used with cellphones and other products because it can be used to store a large amount of data on a single server. In contrast, SQL Server is a closed source database that was created by Microsoft and is commonly used by larger corporations and data science projects. PostgreSQL is another open-source relational database system that is known for its large community of users and active developers. Overall, learning how to use any of the relational database management systems that are compatible with SQL is essential to fully developing your knowledge of this programming language.
Want to Learn More SQL Skills?
As a versatile data science tool, learning SQL introduces a variety of skills into your data science toolkit that can be useful for multiple projects and portfolios. By taking one of Noble Desktop’s data science classes or certificate programs you can learn SQL skills, such as how to organize data, analysis, and querying, as well as how to use different relational database management systems. You can also find SQL classes in your area that are taught live online and in NYC. Noble Desktop also offers an on-demand Intro to SQL seminar for students and professionals that want to learn more about using essential SQL skills for data science.