or simpler and more consistent:

declare @B_counter int
declare @A_counter int

set @B_counter = 0
WHILE @B_counter <= 10 begin
    
    set @A_counter = 0
    WHILE  @A_counter <= 10 begin
        
        SET @A_counter = @A_counter + 1
        print 'inner loop'
    end 

    SET @B_counter = @B_counter + 1
    print 'outer loop'
end
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