- MSSQL: DATEADD(MONTH, @amount, @date)
- MySQL: DATE_ADD(@date, INTERVAL @amount MONTH)
- Oracle: ADD_MONTHS(@date, @amount)
- PostgreSQL: (@date + INTERVAL '@amount MONTH')
The second level of complication are missing functions like correlation:
(Avg(@numericalColumn * @timeColumn) - Avg(@numericalColumn) * Avg(@timeColumn)) / (StdDev_Samp(@numericalColumn) * StdDev_Samp(@timeColumn)) "@columnName"
It's verbose, but doable. However, there is so many functions, for example, in Oracle, that it would be too much work for one person to reach completeness. And if I can't do it myself, I have to rely on the work of others. And if I am relying on the work of others, I have to make it as approachable as possible.