Summary of SQL Server database small knowledge points

I am in the development of a little bit of knowledge to continue to update here ~

1.where conditions change frequently

where userid= ' 1 ' Here's the UserID, its value is often in change, sometimes to check 2, sometimes to check 3, sometimes to check all the people! Here define a function to pass parameters, check all the people here need to make an if branch to judge, but, do not need ~ ~ Good way to

Select  from table Where userid="+userid+"

This is probably the case, the UserID is a parameter, you need to pass directly to me 1 or 2 or other numbers are OK, but you do not need this condition, only need to pass to my UserID this is OK, Userid=userid will find out all the data ~

2. To be Continued ...

Summary of SQL Server database small knowledge points