How does MySQL store data

Question

I looked around Goole but didn\'t find any good answer. Does it store the data in one big file? What methods does it use to make data access quicker than just reading and wr

Answer 1

When you store data in a flat file, it is compact and efficient to read sequentially, but there is no fast way to access it randomly. This is especially true of variable-length data such as documents, names or strings. To allow for fast random access, most databases store information in a single file using a data structure called a B-Tree. This structure allows for insert, deletion, and search to be fast, but it can use up to 50% more space than the original file. Typically, however, this is not an issue as disk space is cheap and larger, while the primary tasks usually require fast access. For more information: http://en.wikipedia.org/wiki/B-tree

Looking carefully into the MySQL docs, we find that indices may be optionally set to "BTREE" or "HASH" type. Inside a single MySQL file, multiple indices are stored which may use either data structure.

Although safety and concurrency are important, these are not WHY databases exist, but added features. The very first databases exist because it is not possible to randomly access a sequential file containing variable length data.