Chapter 2 · 6 levels

Filtering rows

Keep only the rows you need with WHERE: comparisons, AND/OR/IN, date ranges, pattern matching and NULL checks.

Start

Nobody wants all 12,000 orders. They want last month’s refunds, or business customers in Texas, or products that are missing a cost. Filtering is how you turn a table into an answer.

This chapter covers WHERE with comparisons, combining conditions with AND, OR and IN, filtering a timestamp column by date without losing the last day, matching text patterns, and the single most common trap in SQL: comparing with NULL. The boss level is a data quality sweep for the operations team.

Levels

  1. Find refunded orders

    from Rachel Adams, Customer Support Lead

    where, comparison

    Code

  2. Gift ideas under $50

    from Ashley Rivera, Web Content Lead

    and, or, in, precedence

    Code

  3. Orders from March 2024

    from Kevin Brooks, Operations Manager

    dates, timestamp, between, half open range

    Code

  4. Find Gmail customers

    from Lauren Hayes, Email Marketing Manager

    like, ilike, lower, wildcards

    Code

  5. The NULL comparison trap

    from Lauren Hayes, Email Marketing Manager

    null, is null, three valued logic

    Quiz

  6. Boss: data quality sweep

    from Kevin Brooks, Operations Manager

    where, is null, and or, in, date ranges

    Boss · 3 steps