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Implement an in-memory SQL-like table | Valon Mortgage Interview Question

Q: Implement an in-memory SQL-like table

This question evaluates implementation-level skills for in-memory data structures and basic query processing, including projection, filtering, ordering, API design, input validation, and algorithmic efficiency.

Implement a simplified in-memory SQL-like database for a single table.

You should support the following operations on a table with a fixed schema (a list of column names). Each row is a mapping from column name to value (you may assume values are strings or integers and can be compared).

Requirements:

INSERT : Insert a row providing a value for each column.
SELECT with projection : Return rows while selecting only a specified subset of column names (e.g., SELECT colA, colC ).
Filtering : Support a WHERE clause that filters rows by a condition on a column (at minimum, equality like colX = value ; if you choose, you may support additional comparisons).
Ordering : Support ORDER BY <column> (ascending; optionally support descending).

Clarify/handle:

Invalid column names in SELECT/WHERE/ORDER BY.
Rows with missing columns (if disallowed, validate on insert).
Output format: a list of projected rows in the final order.

Design an API (e.g., insert(row), select(columns, where_clause, order_by) or parse SQL strings if preferred) and implement the functionality efficiently for typical interview constraints (up to tens or hundreds of thousands of rows).

Implement a simplified in-memory SQL-like database for a single table.

Requirements:

INSERT : Insert a row providing a value for each column.
SELECT with projection : Return rows while selecting only a specified subset of column names (e.g., SELECT colA, colC ).
Filtering : Support a WHERE clause that filters rows by a condition on a column (at minimum, equality like colX = value ; if you choose, you may support additional comparisons).
Ordering : Support ORDER BY <column> (ascending; optionally support descending).

Clarify/handle:

Invalid column names in SELECT/WHERE/ORDER BY.
Rows with missing columns (if disallowed, validate on insert).
Output format: a list of projected rows in the final order.

Implement an in-memory SQL-like table

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Implement an in-memory SQL-like table

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