6. Filtering Rows with WHERE
Idea: WHERE restricts rows returned. Only rows matching the condition are included.
Shape
SELECT * FROM TableName WHERE Column1 = 'Value';
Multiple Conditions
WHERE Price > 100 AND InStock = 1
Placeholders for Examples
Coming soon: filtering products by price and stock status.
Advanced Deep Dive ADVANCED
Predicate Pushdown: SQL Server tries to apply WHERE as early as possible for efficiency, but computed columns or functions can block this.
Parameterization: Use parameters in WHERE for plan reuse and security (avoid SQL injection).
NULL Handling: WHERE Column IS NULL is required for nulls; = NULL never matches.
Search Arguments (SARGs): Write WHERE clauses so indexes can be used; avoid wrapping columns in functions.
Row Security: SQL Server supports row-level security policies for dynamic WHERE filtering by user.