SQL string Manipulation class coalesce

Source: Internet
Author: User

There must be a case in SQL Server where the values of a column in a table are stitched together into strings, "," or other symbols, which we would normally do:

declare @returnValue nvarchar (max) = ";

Select @returnValue + = ', ' +col1 from Table1 where ....

Set @returnValue =substring (@returnValue, 1,len (@returnValue)-1)--Remove the front,

Then the value of the @returnvalue variable is intercepted, so the operation actually feels very cumbersome to take a look at the internal methods provided by SQL Server implementation:

declare @returnValue nvarchar (max) = "

Select @returnValue =coalesce (@returnValue + ', ' +col1,col1) from Table1 where ....

Individuals prefer the latter way, slightly simpler:

COALESCE (Ex1,ex2,ex3 ...): This method returns the first non-null parameter in a parameter

SQL string Manipulation class coalesce

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