Mysql case statement affecting all rows of a table - mysql

Question

I have a situaiton that has me a bit confused. im using a case statement to update certain rows of a table. the sql query is below, however if i do not specify a value for the column schema_value, then the query will clear it out to null. Here is a copy of the query and table When the query is run, it will null out initialized and test.
any ideas?
UPDATE vals
SET valu
CASE
When name = 'sitename' THEN '$siteame'
When name = 'street' THEN '$stret'
When name = 'city' THEN '$cit'
When name = 'State' THEN '$sate'
When name = 'zipcode' THEN '$ipcode'
When name = 'phone' THEN '$pone'
When name = 'fax' THEN '$fx'
When name = 'social' THEN '$ocial'
END;

Answer 1

Just add an else statement if nothing matches it should keep the original data
UPDATE schema_vals
SET schema_value =
CASE
When schema_name = 'sitename' THEN '$siteame'
When schema_name = 'street' THEN '$stret'
When schema_name = 'city' THEN '$cit'
When schema_name = 'State' THEN '$sate'
When schema_name = 'zipcode' THEN '$ipcode'
When schema_name = 'phone' THEN '$pone'
When schema_name = 'fax' THEN '$fx'
When schema_name = 'social' THEN '$ocial'
ELSE schema_value
END;