Retrieving all data from a table is often just the first step. For meaningful analysis, you usually need to isolate specific subsets of data that meet certain criteria or present the results in a particular sequence. This chapter concentrates on these fundamental data refinement techniques.
You will learn how to use the WHERE clause, the standard SQL mechanism for filtering rows based on conditions you define. We will cover the use of comparison operators (like =, >, <), logical operators (AND, OR, NOT), and specialized operators (IN, BETWEEN, LIKE) for more complex filtering tasks, including how to handle NULL values appropriately. Finally, you will learn to control the presentation order of your results using the ORDER BY clause.
3.1 Introduction to Filtering with WHERE
3.2 Comparison Operators (=, <>, <, >, <=, >=)
3.3 Filtering with AND, OR, NOT
3.4 Filtering with IN and BETWEEN
3.5 Handling NULL Values
3.6 Pattern Matching with LIKE
3.7 Sorting Results with ORDER BY
3.8 Hands-on Practical: Filtering and Sorting Queries