Which clause is mandatory in a SELECT statement?

In a SELECT statement, the FROM clause is essential because it specifies the table from which to retrieve the data. Without the FROM clause, the database management system would not know where to pull the requested data, making it impossible to execute the query correctly. This clause defines the context for the query, indicating the source of the data, which is a fundamental requirement in SQL syntax.

In contrast, the WHERE, ORDER BY, and GROUP BY clauses serve specific functions that enhance query results but are not mandatory for a SELECT statement to be valid. The WHERE clause filters records based on specified conditions, the ORDER BY clause sorts the results, and the GROUP BY clause organizes results into aggregated groups. Each of these clauses can improve the quality and relevance of the output, but they are not required for a basic SELECT statement to function.