unique mysql query

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

MySQL Query performance optimizationThe optimization of MySQL query performance involves many aspects, including library table structure, establishing reasonable index and reasonable query. The library table structure includes how to design

" Guide "When talking to a friend or colleague about the MySQL query cache function, the individual likes to compare the query cache function to the Litchi , is very nutritious things, but once eat too much, it is easy to get angry and nosebleeds,

Essays-66 Articles-0 comments-MySQL slow query (ii)-Pt-query-digest detailed slow query log one, Introduction Pt-query-digest is a tool for analyzing MySQL slow query, it can analyze Binlog, Gene RAL Log, Slowlog, can also be analyzed via

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 tutorial How to use the unique index Grammar:UNIQUE KEY ' test ' (' Xref_key ', ' xref_dbname ')UNIQUE KEY ' Xref_key ' (' Xref_key ', ' xref_dbname ') The above syntax checks whether the combination of Xref_key and Xref_dbname is a unique

In mysql, key, primary key, unique key and index are different, mysqlunique Indexes in mysql are very important knowledge points. Compared with other knowledge points, indexes are more difficult to master, and there are many index types in mysql,

An introduction The principle of two indexes Three-indexed data structures Three MySQL index management Four Test indexes Five correct use index Six query optimization artifact-explain The basic steps of seven-slow query

Question 1: What are the differences between mysql index types normal, unique, and fulltext? Normal: Indicates normal index unique: Indicates unique and duplicate indexes are not allowed. If the field information is not repeated, for example, when

The purpose of creating a unique index is not to improve access speed, but to avoid duplication of data. A unique index can have more than one but the value of the indexed column must be unique, and the value of the indexed column allows null values.