SSC IMD SA 2017 – Question 189

Which of the following are steps in query processing?

• Parsing and translation
• Optimization
• Evaluation
• All options are correct

Detailed Explanation:

The correct answer is d) All options are correct (सभी विकल्प सही हैं).

In a Relational Database Management System (RDBMS), Query Processing refers to the complete sequence of activities involved in transforming a high-level declarative query (SQL) into low-level execution instructions. The three foundational phases are:

1. Parsing and Translation (पदच्छेद और अनुवाद): The database parser checks the SQL statement for correct syntax and verifies table/column names against the database system catalog (semantic check). It translates the query into an internal relational-algebra expression or parse tree.
2. Optimization (अनुकूलन): The Query Optimizer considers multiple logically equivalent relational-algebra expressions and various access paths (indices, join algorithms like hash-join or merge-join). Using catalog cost statistics, it selects the execution plan with the lowest estimated execution cost.
3. Evaluation (मूल्यांकन): The query-execution engine takes the optimal evaluation plan, executes the operations against physical database files, and returns the query results to the user.

Because Parsing/Translation, Optimization, and Evaluation are all core phases, option d is correct.