mysql UNIQUE constraint
Translation results：
UK [juˈni:k] US [juˈnik]
adj. Only, only; unique, unique; unusual, special; extraordinary
mysql UNIQUE constraintsyntax
Function: UNIQUE constraint uniquely identifies each record in the database table.
Description: UNIQUE and PRIMARY KEY constraints both provide uniqueness guarantees for columns or column sets. PRIMARY KEY has automatically defined UNIQUE constraints. Note that you can have multiple UNIQUE constraints per table, but you can only have one PRIMARY KEY constraint per table.
mysql UNIQUE constraintexample
//Create a UNIQUE constraint on the "Id_P" column when the "Persons" table is created
CREATE TABLE Persons(Id_P int NOT NULL,LastName varchar(255) NOT NULL,FirstName varchar(255),Address varchar(255),City varchar(255),UNIQUE (Id_P));
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