Star schema is a denormalized model with one or more fact table is surrounded by number of fact table. The whole diagram itself it depicts a star called star schema.Advantage is star schema:
1.Contains lesser no of joins
2.Contains lesser no of queries, so queries result fastly.
Disadvantage of star schema:
If the dimension table is very huge in that case data redundancy will be there.Snowflake schema is based on normalization like normalize the dimension table to remove redundancy and dependancy. If star schema consists of a huge dimension table then we will broken that table into a no of dimension table.
Advantage of snow flake schema:
1.Non redundant data
2.Flexible
3.Easy to maintain
Disadvantage of snowflake schema:
1.Query performance go down as it needs more join to retrieve data.
Basically based on business needs and if the dimensional table is huge, go for snow flake schema and if there is one denormalized dimensional table go for star schema