Print Output variable value in SQL

In SQL Server query and analysis, when executing a dynamic SQL statement, you sometimes need to print the value of a variable for a runProgramIs it true,

Similar:

Declare @ STR varchar (2000)/***** set @ STR = 'start :'****/

Select top 3 @ STR = @ STR + title from navwhere (ID <9) print @ Str

The program runs normally but does not see the print output result

However, when we put the above/***** set @ STR = 'Start:' *****/, we will see the print result after reading this sentence.

Cause: @ STR is defined and no initialization value exists.

The above is my personal summary of some small experience,