There are four types of schemas are available in data warehouse. Out of which the star schema is mostly used in the data warehouse designs. The second mostly used data warehouse schema is snow flake schema.We will see about these schemas in detail.tar Schema: A star schema is the one in which a central fact table is sourrounded by denormalized dimensional tables. A star schema can be simple or complex. A simple star schema consists of one fact table where as a complex star schema have more than one fact table.
Sandstorms -- also called duststorms -- are caused by strong winds blowing over loose soil or sand, and picking up so much of that material that visibility is greatly reduced. The widespread abundance of loose sand in deserts makes them the most common locations for sandstorms to form.In desert regions at certain times of the year, sandstorms become more frequent because the strong heating of the air over the desert causes the lower atmosphere to become unstable.This instability mixes strong winds in the middle troposphere downward to the surface, producing stronger winds at the surface.he widespread abundance of loose sand in deserts makes them the most common locations for sandstorms to form. In desert regions at certain times of the year, sandstorms become more frequent because the strong heating of the air over the desert causes the lower atmosphere to become unstable.
Thunderstorms What is a thunderstorm? A thunderstorm is a storm with lightning and thunder. Its produced by a cumulonimbus cloud, usually producing gusty winds, heavy rain and sometimes hail. What causes a thunderstorm? The basic ingredients used to make a thunderstorm are moisture, unstable air and lift. You need moisture to form clouds and rain. You need unstable air that is relatively warm and can rise rapidly. Finally, you need lift. This can form from fronts, sea breezes or mountains. When are thunderstorms most likely to occur? Thunderstorms can occur year-round and at all hours.