What is an index: The index is a table of contents, and you can quickly locate the query data by looking at the index location in the catalog before finding it. For the index, it is saved in an extra file. The index is made up of one or more columns in the database, which is useful for increasing the query speed of the data in the table. The advantage of indexing is that the index of index data can be improved by the disadvantage of creating and maintaining indexes that require time-consuming indexing to increase query speed, slow down the normal index of write speed, basic index type, no unique limitations, and the only advantage is faster access to data. Using normal indexes is generally used in the presence of query conditions or sorting criteria. A unique index is unique when the value of the indexed column should appear once, compared to a normal index. Primary key index The primary key index is a unique index. A primary key uniquely identifies a row in a table. There can be only one primary key in a table. An index based on a primary key is called a primary key index. Full-text indexed full-text indexing can be created in a varchar or text Type field. The purpose of full-text indexing is to solve the problem of inefficient fuzzy queries. In full-text search, the data of like query is relatively large and inefficient. Full-text indexing improves efficiency in full-text search of data reference: http://www.cnblogs.com/renfanzi/p/5742650.html#_label0http://blog.csdn.net/load_life/ article/details/7908388
The index in MySQL
