Say I have column A with 10000 distinct values column B and C with 2 distinct values and for simplicity sake the column type is an int.
If I wanted a composite key why should I make the order of the key A,B,C I read someplace that faster lookups happen with the leftmost index, being an index with a large cardinality. Is this true? Is this a hook for the optimizer? What is the internal logic for mySQL that makes this so? Is this a myth and have I been misled? -- Dathan
