GROUP BY clause

Some databases allow you to specify a column index in the GROUP BY clause:
SELECT a, b, sum(c) FROM table GROUP BY 1,2

This is not possible with all database servers:

Table 1. Database server support of GROUP BY column index
Database Server Type GROUP BY colindex, ... ?
IBM® DB2® LUW No
IBM Informix® Yes
IBM Netezza No
Microsoft™ SQL Server No
Oracle® MySQL / MariadDB Yes
Oracle Database Server No
PostgreSQL Yes
SAP HANA® No
SQLite Yes

Search for GROUP BY in your SQL statements and use explicit column names.