Bitmap indexes

- [Instructor] Let's take a look … at a special kind of index that is well-suited … for low cardinality columns. … That is the Bitmap Index. … Bitmap Indexes store a series of bits … for indexed values. … The number of bits used is the same … as the number of distinct values in a column. … For example, a column that has either a yes or no value … would require two bits. … One corresponding to the yes, … and one corresponding to the no. … Now, we aren't restricted to bullion, … or yes no columns. … We could have three or more values. … For example, if we have a pay type, … which can have three possible values, … then we would use three bits to represent each value. … One of the advantages of Bitmap Indexes … is that we can perform bullion operations quickly. … For example, performing an and operation on two bitmaps … is a fast operation. … So we could use it to find all union members … who have an hourly pay type in our example. … Bitmap's are used with low cardinality columns, … especially when we want to filter on those columns …