SQL Loop through records and replace

use DB_Name

DECLARE @var_1 as nvarchar(300)

DECLARE @var_2 as int --DECLARE @VariableName as Variable DataType

                                              --You can DECLARE many variable seperated by comma

                                              --to add another variable to the previous declaration use this example

                                              --,

                                              --@Variable2 as char

                             

DECLARE cursor_ CURSOR FOR   --declare the cursor

SELECT    primary_key_column_name , column2         --write a correct select statmen

FROM dbo.TableName

OPEN cursor_      --Open the cursor

FETCH NEXT FROM cursor_ INTO @var_1, @var_2  -- filling the variables using the cursor

WHILE (@@FETCH_STATUS = 0)        --Looping through the cursor

  BEGIN                             --Write you code here to do what you want

if(@var_2='null' or @var_2='NULL' OR @var_2='Null')

   UPDATE dbo.Channels SET var_2=column_name_to_be_replaced_with

   WHERE primary_key_column_name=@var_1

   FETCH NEXT FROM cursor_ INTO @chanID_, @chanName_Ar_ --To move the cursor to the next row

  END

  CLOSE cursor_                       --You have to close the cursor

  DEALLOCATE cursor_                  --You have to free the memory