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CREATE UNIQUE INDEX. The CREATE UNIQUE INDEX command creates a unique index on a table (no duplicate values allowed) Indexes are used to retrieve data from the database very fast. The users cannot see the indexes, they are just used to speed up searches/queries.
Unique indexes are indexes that help maintain data integrity by ensuring that no rows of data in a table have identical key values. When you create a unique index for an existing table with data, values in the columns or expressions that comprise the index key are checked for uniqueness.
A unique index can be created on a single column or on a combination of multiple columns, depending on the requirements of the database schema. The purpose of a unique index is to provide a fast and efficient way to enforce data integrity by preventing duplicate entries in a table.
5 maj 2023 · This topic describes how to create a unique index on a table in SQL Server by using SQL Server Management Studio or Transact-SQL. A unique index guarantees that the index key contains no duplicate values and therefore every row in the table is in some way unique.
Indicate that a clustered or a nonclustered index is created for the PRIMARY KEY or UNIQUE constraint. PRIMARY KEY constraints default to CLUSTERED, and UNIQUE constraints default to NONCLUSTERED. In a CREATE TABLE statement, CLUSTERED can be specified for only one constraint.
13 cze 2016 · We can enforce uniqueness of values in specific column(s) in a SQL Server table by creating a unique constraint or a unique index on those column(s). Read this tip to learn about the difference.
3 dni temu · A PL/SQL Unique Index is a powerful database object used to ensure the uniqueness of values in one or more columns of a table. In Oracle databases, indexes play an important role in enhancing query performance by enabling quick retrieval of rows.. The unique index specifically enforces a rule that no two rows in a table can have the same values for the indexed column(s).
