what is mysql index

The index in MySQL means index. It is a data structure used to speed up the query of database tables. The index can be compared to the catalog of a book. It stores the values ​​​​of specific columns in the table and the corresponding row positions, making the database more efficient. Locate and access data quickly. The function of the index is to improve query efficiency. Without an index, the database needs to scan the entire table row by row to find matching data. This method will be very time-consuming in large tables. With an index, the database can The required data rows are quickly located in the order, which greatly improves the query speed.