Remove two spaces from the SQL trim () function

1. Remove two spaces from the SQL trim () function
The SQL syntax does not directly remove spaces at both ends, but ltrim () removes the left space rtrim () and the right space.
The SQL trim () function is used together, that is, select ltrim (rtrim (usrname ))

 

2. Select multiple columns for distinct, one of which cannot be repeated, and the other columns take the maximum value.
Goodname goodversion
Item 1.0
Item 2.0
Item 2 1.0
Item 2 2.0
If you want
Item 2.0
Item 2 2.0
Select distinct goodname, goodversion from... No.
When distinct acts on two columns, the two columns are repeated at the same time.
Therefore, a special method is used for processing.
Select max (goodname), max (goodversion) from t_good group by goodname
Grouping with goodname ensures that goodname does not repeat.

 

3. Set the date field to null in SQL Server and use the backspace key to clear the field.
Update Table1 set mydate = NULL;