Library › Book 15 › Filtering and Sorting -- Finding the Needle in the Haystack
Filtering and Sorting -- Finding the Needle in the Haystack
2.1🔒The WHERE Clause in DepthThe WHERE clause filters rows based on conditions. Think of it as the "search criteria" for your query.
2.2🔒Combining Conditions with AND, OR, NOTCommon Mistake: Forgetting parentheses when combining AND and OR. WHERE role = 'admin' OR role = 'editor' AND active = true evaluates as…
2.3🔒Pattern Matching with LIKE and ILIKE
2.4🔒Working with NULLNULL is special in SQL. It is not a value -- it is the absence of a value. You cannot compare to NULL with =.
2.5🔒The IN Operator
2.6🔒Sorting with ORDER BY
2.7🔒Limiting Results with LIMIT and OFFSETPro Tip: When testing pagination in your application, verify it with SQL. Fetch page 1 and page 2 via the API, then run a single SQL query…
2.8🔒Practice Schema 2: E-Commerce Orders
2.9🔒ExercisesBeginner:
2.10🔒Q&AResume phrasing- Designed SQL-based data investigation queries using WHERE, LIKE, IN, and ORDER BY to isolate production anomalies, reducing average bug…
2.11🔒Q&ACover letter framingI use SQL filtering as a diagnostic tool, not just a retrieval mechanism. When a bug report comes in, I write targeted WHERE clauses to…
2.12🔒Q&AInterview framing"I approach data investigation by layering filters methodically. I start broad -- how many records exist -- then narrow with WHERE…
2.13🔒Q&AWhat not to say- "I just use equals comparisons in my WHERE clauses." -- This misses NULL handling, pattern matching, and range queries entirely. - "NULL…
2.14🔒Q&AQuestion 1Prompt: Your application's product listing page shows products sorted by price ascending, but a customer reports that page 2 of results…
2.15🔒Q&AQuestion 2Prompt: You are investigating a bug where some users report their accounts are "deleted" but they can still log in. Describe how you would…
2.16🔒Q&AQuestion 3Prompt: A data analyst asks you to help verify that the reporting dashboard's "orders by status" breakdown is accurate. The dashboard shows…
2.17🔒Q&AQuestion 4Prompt: You need to find all orders where the delivered_at timestamp is earlier than the shipped_at timestamp -- a data integrity issue…