Teradata中不同月份的時間日期計算

Question

如何在Teradata中計算以下內容：

Beginning Of Previous Month, 
End Of Previous Month, 
Beginning Of Six Months Ago, 
Beginning Of Twelve Months Ago

謝謝。

Answer 1

Beginning Of Previous Month:    add_months(current_date - (extract(day from current_date)-1), -1) 
End Of Previous Month:                     current_date - (extract(day from current_date))
Beginning Of Six Months Ago:    add_months(current_date - (extract(day from current_date)-1), -6) 
Beginning Of Twelve Months Ago: add_months(current_date - (extract(day from current_date)-1), -12) 

根據您的版本，可能會有一些功能：

td_month_begin(add_months(current_date,-1))
last_day(add_months(current_date,-1))

或者，您可以檢查（希望）現有的日歷表（如果已存在）。