Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_19833 ( "Stage" real, "Winner" text, "General classification" text, "Points classification" text, "Mountains classification" text, "Combination classification" text, "Team classification" text )

### Question ###
How many combination classifications have the winner as Erik Zabel and a points classification as Alessandro Petacchi

### Accurate SQL ###

SELECT COUNT("Combination classification") FROM table_19833 WHERE "Points classification" = 'Alessandro Petacchi' AND "Winner" = 'Erik Zabel'