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To name a UNIQUE constraint, and to define a UNIQUE constraint on multiple columns, use the following SQL syntax: ALTER TABLE Persons ADD CONSTRAINT UC_Person UNIQUE (ID,LastName);
To add a unique constraint, you need to use two components: ALTER TABLE - to change the table schema and, ADD UNIQUE - to add the unique constraint. You then can define your new unique key with the format 'name'('column1', 'column2'...) So for your particular issue, you could use this command:
If you define a UNIQUE constraint without specifying a name, MySQL automatically generates a name for it. To define a UNIQUE constraint with a name, you use this syntax: [CONSTRAINT constraint_name] UNIQUE(column_list) Code language: SQL (Structured Query Language) (sql)
The UNIQUE constraint in MySQL ensures distinct values in a column or a set of columns. This constraint acts as a gatekeeper ensuring that every data entered into the column or group of columns remains unique.
10 lip 2024 · MySQL UNIQUE constraint is different from PRIMARY KEY constraint as, primary key can not have null values and can only be used once in a table. In this article, we have covered how to use UNIQUE constraint with CREATE TABLE and ALTER TABLE statements.
This MySQL tutorial explains how to create, add, and drop unique constraints in MySQL with syntax and examples. A unique constraint is a single field or combination of fields that uniquely defines a record.
26 sty 2024 · This tutorial will guide you through understanding and applying the UNIQUE constraint, from the basics to advanced examples. What is the UNIQUE Constraint? In MySQL, the UNIQUE constraint is a way to ensure that all values in a column or a set of columns are distinct across all the rows in the table.
