Filtering Data
4 Topics
1
AND, OR, and NOT
Combining multiple query filter conditions.
Logical operator precedence and three-valued logic (TRUE/FALSE/UNKNOWN) are common interview topics. Interviewers test whether you can write complex filters correctly and understand how NULL affects boolean evaluation.
2
BETWEEN and IN
Range selection and matching arrays of values.
BETWEEN and IN are tested to evaluate whether candidates understand inclusive/exclusive ranges, date boundary handling, and the performance differences between IN with a list vs. IN with a subquery.
3
LIKE, ILIKE, and Wildcards
Case-sensitive and case-insensitive pattern matching.
Pattern matching with LIKE/ILIKE is tested in interviews to evaluate string filtering skills, understanding of wildcard characters, and awareness of performance implications with leading wildcards.
4
IS NULL and IS NOT NULL
Filtering empty or uninitialized table cells.
NULL handling is one of the most frequently tested SQL interview topics. Interviewers evaluate whether you understand three-valued logic, the difference between NULL and empty strings, and how NULL affects aggregates and JOINs.