The SET Datefirst statement in SQL Server set the First day of the week for the current session. This setting affect how date related function are operations interpret the day of the week. If our default language is US English , then by default 7 (Sunday) is set as the First day.
Value for the set Datefirst
|
Value |
First day of the
week |
Comment |
|
1 |
Monday |
Default for many
Europe countries |
|
2 |
Tuesday |
|
|
3 |
Wednesday |
|
|
4 |
Thursday |
|
|
5 |
Friday |
|
|
6 |
Saturday |
|
|
7 |
Sunday |
Default in US |
|
select
@@datefirst as 'First day of the week' |
It returns 7. In my system default language is US English.
We can also set the Datefirst for a day. Let’s see here we
want to set the first day as Tuesday.
Set DateFirst 2
Set Datefirst is session level
setting. It will impact only an session level and it do not change the global
setting for the SQL Server. It affect DatePart(wwekday,date) but not
Format(date,ddd).
Always set Datefirst before using
the datepart to ensure consistency.
