I'm trying to update the column visited to give it the value 1. I use MySQL workbench, and I'm writing the statement in the SQL editor from inside the workbench. I'm writing the following command:

UPDATE tablename SET columnname=1;

It gives me the following error:

  
You are using safe update mode and you tried to update a table without
  a WHERE that uses a KEY column To disable safe mode, toggle the option
  ....

I followed the instructions, and I unchecked the safe update option from the Edit menu then Preferences then SQL Editor. The same error still appear & I'm not able to update this value. Please, tell me what is wrong?