Final answer:
Column names must be prefixed by table names in join syntax when the same column name appears in more than one table involved in the query to avoid ambiguity and correctly direct the database which table to pull data from.
Step-by-step explanation:
In SQL and when working with databases, column names must be prefixed by table names in join syntax when the same column name appears in more than one table involved in the query. This is necessary to avoid ambiguity and ensure that the database understands from which table to retrieve the data. Including the table name is crucial, especially in complex queries where multiple tables have columns with the same name.
It is not a matter of one table being more correct than another; rather, it is about clarity in the query's definition. The way data is grouped can be varied based on the requirements of the query, and there can be advantages to different methods of grouping depending on the use case. For example, summarizing or partitioning data can optimize performance or make the dataset more manageable. The selection of the grouping method might lead to switching between tables when analysing the data because different tables may hold relevant data that supports the analysis goal.
Therefore, prefixing column names with table names is not influenced by query speed, the number of tables participating in the join, nor is it never required—it is essential when the same column name is found in multiple tables used in the query.