Outcomes
- • Combine conditions safely with AND / OR / NOT.
- • Handle ranges, sets, patterns, and nulls without logic bugs.
- • Write filters that match business rules exactly.
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Beginner4 lessons + 3 bonus
Filtering & Logic
Stop returning too many rows. Master WHERE clauses with AND, OR, LIKE, IN, BETWEEN, and NULL handling — the difference between a query that works and one that almost works.
Fast SQL learning loop
- • Read the prompt and schema before writing.
- • Run early and often to validate each clause.
- • Compare expected output shape, not just syntax validity.
Professional learning blueprint
Learn to isolate exactly the right rows using precise SQL logic.
Real-world use
- • Compliance filters and eligibility checks.
- • Customer segmentation for ops and marketing teams.
- • Data cleaning and audit views for analytics pipelines.
Fast study plan
- 1. Validate every filter by running row-count checks.
- 2. Add one condition at a time and test incremental changes.
- 3. Keep a checklist for null-handling and boundary values.
Deep learning journey
Filtering and Reasoning Arc
Write precise business filters with confidence across ranges, nulls, and boolean conditions.
Boolean logic control
Combine AND/OR/NOT correctly using grouped conditions.
- • Parenthesis precedence
- • Incremental filter building
- • Rule-to-SQL translation
Pattern and range matching
Use BETWEEN, IN, LIKE, and date ranges safely.
- • Inclusive/exclusive boundaries
- • Pattern matching
- • Set membership checks
Null-safe logic
Avoid silent data loss caused by NULL behavior.
- • IS NULL / IS NOT NULL
- • COALESCE
- • IS DISTINCT FROM
Bonus lesson units
Additional lessons to master this track (3)
1. Regular expression filtering
Use ~ and REGEXP_LIKE for advanced pattern matching beyond LIKE and ILIKE.
2. Date and time range filtering
Filter by DATE_TRUNC, EXTRACT, and interval arithmetic for calendar-aware queries.
3. Anti-join patterns
Compare NOT IN, NOT EXISTS, and LEFT JOIN IS NULL for finding unmatched rows — and when each is safest.
Expanded practice
Mission exercises (10)
1. Eligibility filter
easyFilter employees by department, salary floor, and hire date threshold.
2. Compliance exclusion
mediumExclude rows by multi-rule policy with grouped OR conditions.
3. Date-range hiring set
mediumReturn hires within a target month range with explicit boundaries.
4. Null-safe contact check
mediumReturn employees missing email/phone with clear null logic.
5. Pattern targeting
easyFind employee emails with specific domain patterns and case handling.
6. NOT logic challenge
mediumRewrite a complex negative filter into a readable positive equivalent.
7. Range segmentation
hardClassify rows into compensation ranges and filter by selected segments.
8. Multi-policy filter
hardImplement three business policies in one WHERE clause with comments.
9. Set inclusion audit
easyUse IN/NOT IN safely and explain null pitfalls in output notes.
10. Filter correctness test
mediumRun count checks before/after each condition to prove logic correctness.
Study references
What to study next
The WHERE clause is where most queries succeed or fail. This course teaches you to write predicates that return exactly the rows you mean — no more, no less.
What you'll learn
- Combine conditions with
AND,OR, andNOT - Match a list of values with
INandNOT IN - Check numeric or date ranges with
BETWEEN - Pattern-match text with
LIKE(%wildcard) andILIKE(case-insensitive) - Handle missing data correctly with
IS NULLandIS NOT NULL - Control evaluation order with parentheses (why
ANDbinds tighter thanOR)
What you'll practice on
The HR database and the Store database. You'll filter employees by salary range and hire date, find customers by name pattern, and write conditions that correctly handle rows where data is missing.
Prerequisites
SQL Fundamentals (or equivalent — you should know SELECT, FROM, and basic WHERE).