do you mean the a single record's column value? UPDATE <table name> SET <column name> = <value> WHERE <column name> = <old value>; leave off the WHERE line if you want to set all values for the column to zero This works in T-SQL. I assume it will work in mysql.
We need more information to be able to churn out a query, like how the database tables etc. are set up, and how you identify the value you want to change.