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To create a UNIQUE index, you use the CREATE UNIQUE INDEX statement as follows: CREATE UNIQUE INDEX index_name. ON table_name(index_column_1,index_column_2,...); Code language: SQL (Structured Query Language) (sql) Another way to enforce the uniqueness of value in one or more columns is to use the UNIQUE constraint.
CREATE UNIQUE INDEX Syntax. Creates a unique index on a table. Duplicate values are not allowed: CREATE UNIQUE INDEX index_name. ON table_name (column1, column2, ...); MySQL CREATE INDEX Example. The SQL statement below creates an index named "idx_lastname" on the "LastName" column in the "Persons" table: CREATE INDEX idx_lastname.
CREATE INDEX enables you to add indexes to existing tables. CREATE INDEX is mapped to an ALTER TABLE statement to create indexes. See Section 15.1.9, “ALTER TABLE Statement”. CREATE INDEX cannot be used to create a PRIMARY KEY; use ALTER TABLE instead.
5 Ιαν 2024 · The syntax for creating a UNIQUE INDEX involves the CREATE INDEX statement. Creating a UNIQUE INDEX on a Single Column: CREATE UNIQUE INDEX index_unique_column ON tbl_name (col_name); Creating a UNIQUE INDEX on Multiple Columns: CREATE UNIQUE INDEX index_unique_columns ON tbl_name (co1, col2, ...); Exmaples of MySQL Unique Index.
A MySQL unique index is a special index that not only speeds up data retrieval from a table, but also prevents duplicate values from appearing in one or more specified columns. MySQL allows you to use the CREATE UNIQUE INDEX statement to create a unique index.
You can use this syntax to add an index and control the kind of index (HASH or BTREE). create index your_index_name on your_table_name(your_column_name) using HASH; or. create index your_index_name on your_table_name(your_column_name) using BTREE;
A unique index can be created on one or more columns of a table using the CREATE UNIQUE INDEX statement in MySQL. If we are creating unique index on only a single column, all the rows in that column must be unique.
