What Does 'GROUP BY 1' Mean in SQL Queries?

Understanding the Significance of "GROUP BY 1" in SQL Queries

In database management systems, the "GROUP BY" clause plays a crucial role in aggregating and summarizing data. Recently, a user encountered a SQL query that contained a peculiar "GROUP BY" clause: "GROUP BY 1." This raised the question of whether it was a simple typo or had a specific purpose.

To shed light on this query, it's important to understand that each column in the result set of a SQL query has a corresponding ordinal number, starting from 1. Thus, "GROUP BY 1" effectively means grouping the data based on the first column of the result set.

This technique is commonly used to perform aggregations on data when the specific column names are not known or are not relevant to the query. For instance, if a query retrieves data from multiple tables and each table has a column named "Name," using "GROUP BY 1" allows the user to group the rows by the first instance of the "Name" column, regardless of its origin.

Similarly, the "ORDER BY" clause can be used in conjunction with an ordinal number to sort the results based on the specified column. For example, "ORDER BY 2" would sort the results based on the second column of the result set.

Therefore, while "GROUP BY 1" may appear unconventional at first glance, it serves a valuable purpose in SQL queries by enabling grouping and sorting based on ordinal numbers rather than specific column aliases.

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