T-sql first day of month

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- T sql first day of month function
- T sql get first day of month
- T sql get first day of month from date
- T sql first day of previous month
- T sql first day of last month
- T sql first day of next month
- T sql get first day of previous month
- T sql get first business day of month
- Tsql first day of month from date
- T sql first and last day of current month