Learn T-SQL Querying

The perils of SELECT *

SELECT * should be avoided in stored procedures, views, and multi-statement table-valued functions (MSTVF) because our T-SQL code might break if there are any changes to the underlying schema. For example, applications that reference SELECT * may be relying on the ordinal position rather than column names and may encounter errors if the underlying table definition is changed. Instead, fully qualify the names of columns that are relevant for our result set.

This also has important performance implications. Some application patterns may rely on reading an entire dataset and applying filters in the client layer only. For example, imagine a web application where a sales supervisor can see a report of orders registered for ...