First, you need to know the following bits of information:
Database Name
For this purpose, we will call the database name “DATABASE”
Table Name
For this purpose, we will call the table name “TABLE”
Column A (Where the data will come from)
For this purpose, we will call this column “COLUMNA”
Column B (Where the data is going to)
For this purpose, we will call this column “COLUMNB”
SELECT TABLE, COLUMNA, COLUMNB FROM TABLE
UPDATE TABLE SET COLUMNB = COLUMNA