mysql index key

MySQL index details, MySQL index detailsI. Introduction to index basics 1.1 In MySQL, indexes are also called keys. They are a data structure that the storage engine uses to quickly find records. Indexes are critical to good performance. Especially

Key differs from primary keyKey is usually the index synonym. If the keyword attribute primary key is given in the column definition, then primary key can also be specified as key only. The purpose of this is to be compatible with other database

The concept of MySQL indexingAn index is a special kind of file (an index on a InnoDB data table is an integral part of a table space), and they contain reference pointers to all records in the datasheet. More generally, the database index is like a

Concept:A primary key (primary key) uniquely identifies a property or group of properties for a row in a table. A table can have only one primary key, but there may be multiple candidate indexes. Primary keys often form referential integrity

MySQL common index, unique index, primary index, foreign key index, composite index, full-text index usage, mysql full-text index1. Common Index The only task of a common INDEX (INDEX defined by the KEY or INDEX keyword) is to speed up data access.

Transferred from: http://blog.csdn.net/duck_arrow/article/details/8264686Concept:A primary key (primary key) uniquely identifies a property or group of properties for a row in a table. A table can have only one primary key, but there may be multiple

I. What is an index?Indexes are used to quickly look for records with specific values, and all MySQL indexes are saved as B-trees. If there is no index, MySQL must start scanning all records of the entire table from the first record until it finds a

1. General Index The only task for a normal index (an index defined by the keyword key or index) is to speed up access to the data. Therefore, it should be only for those that most often appear in the query condition (where column = ...). or the

One: Field modifier1:null and NOT NULL modifiersLet's take a look at this example.Mysql> CREATE TABLE worker (ID int not null,name varchar (8) Not null,pass varchar (a) not null);Mysql> INSERT into worker values (1, ' HA ', ' 123456 ');Mysql> INSERT

Understanding MySQL-index and optimization summary, mysql Index Summary Preface: indexes have a crucial impact on the query speed. Understanding indexes is also the starting point for optimizing database performance. Consider the following: Assume