SQL Server data type Conversion small experiment _mssql

1.   DECLARE @i int
   Set @i= ' a '
   Set @i=cast (' a ' as int)
   Set @i=convert (int, ' a ')
   Print @i--The output is: syntax error occurs when converting varchar value ' A ' to a column with a data type of int. This is not the same as Java

3. DECLARE @ch varchar (90)
   Set @ch =97
   Print @ch

   --The display result is 97, which means that the implicit conversion to a string

5. DECLARE @ch varchar (90)
   Set @ch =97+ ' a '
   Print @ch

   --The output is: syntax error occurs when converting varchar value ' A ' to a column with a data type of int. Why not first convert the number 97 to a string and then connect to ' a ', is it because 97 was in the front, so SQL Server tried to do it? Let's change the position .

7. DECLARE @ch varchar (90)
   Set @ch = ' A ' +97
   Print @ch

   --The output is: syntax error occurs when converting varchar value ' A ' to a column with a data type of int. I don't understand why SQL Server always has to convert ' a ' to a number first and cause failure.