Databases are one of the cornerstones of modern businesses. Data retrieval is usually made with a SELECT statement and it's therefore very important that you are familiar with this part of your journey. Retrieved data is often not organized in the way you want it to be, so it requires additional formatting. Besides formatting, accessing very large amounts of data requires you to take into account the speed and manner of query execution, which can have a major impact on system performance.
This chapter will be your guide through the basic elements of the SELECT statement, the last of the DML commands that we haven't yet covered in detail. To cover all the elements and scenarios we would need at least another book.
We will cover the following topics:
- Retrieving and filtering data
- Summarizing data
- Querying multiple tables