Correct Answer:
D. Submit
In SQL (Structured Query Language), Submit is NOT a valid keyword for database operations. SQL uses a well-defined set of commands to interact with databases. Keywords like DELETE, INSERT, and UPDATE are fundamental Data Manipulation Language (DML) commands that allow users to modify the data stored within database tables. While the concept of 'submitting' data might be familiar in web forms or application interfaces, it has no direct, standard SQL keyword counterpart for performing database transactions or data modification. Standard SQL uses `COMMIT` or `ROLLBACK` for transaction control, not `SUBMIT`.
- A: Delete: DELETE is a valid SQL command used to remove existing rows from a table based on specified conditions. It is a core DML operation.
- B: Insert: INSERT is a valid SQL command used to add new rows of data into a table. It is another fundamental DML operation for populating a database.
- C: Update: UPDATE is a valid SQL command used to modify existing data in one or more columns for rows that meet certain criteria within a table. It is also an essential DML operation.