mysql select unique values

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

This article describes how to insert duplicate values in the unique column in mysql. it is mainly based on the mysql platform. through these solutions, you can implement some new functions and applications. This article will be shared here with

This article will introduce the differences between unique and primary constraints in mysql. unique and primary are the types we often use when creating mysql. Next I will introduce them to you. Fields defining the UNIQUE constraint cannot contain

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

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,

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

A field that defines a unique constraint cannot contain duplicate values, you can define a unique constraint for one or more fields, so unique can be defined at the field level or at the table level, and the field on a unique constraint can contain

How to Use distinct to query multiple unique record values in mysql How to Use distinct to query multiple unique record values in mysql When using mysql, you sometimes need to query records with unique fields. Although mysql provides the keyword

MySQL常用指令，java，php程序员，数据库工程师必备。程序员小冰常用资料整理MySQL common commands (for reference)The most common display commands are:1. Display the list of databases.show databases;2. Display the data table in the library:Use MySQL;Show tables;3, display the

I used to use SQLServer for Table Partitioning. I encountered a lot of questions about unique indexes. Today I want to know some knowledge about unique indexes in MySQL, including how to create and batch insert, there are also some tips for SQL. If