Should You Use SELECT * or Specify Columns in SQL Queries?

**Explicitly specifying columns is preferable to using SELECT***

When writing SQL statements, the traditional rule of thumb is to avoid using SELECT * and instead list the exact column names required. Does this still work when selecting all columns from the table?

The answer is yes. Even if all columns are retrieved, specifying column names one by one using methods such as SELECT column1, column2, column3, ... is more efficient than using SELECT *.

This performance difference results from the reduced likelihood that SQL Server will access table data rather than the index, which is possible when selecting specific columns. By explicitly listing the required columns, the database is more likely to utilize existing indexes rather than scanning the entire table.

Additionally, specifying columns makes the code more resilient to schema changes. If the table schema is modified in the future, the consuming code will still receive the same data structure even if columns are added. This robustness eliminates the need to update code as the schema evolves.

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