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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. When you create a UNIQUE ...
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; You can learn about differences between BTREE and HASH indexes here: http://dev.mysql.com/doc ...
The SQL statement below creates an index named "idx_lastname" on the "LastName" column in the "Persons" table: CREATE INDEX idx_lastname. ON Persons (LastName); If you want to create an index on a combination of columns, you can list the column names within the parentheses, separated by commas: CREATE INDEX idx_pname.
4 Ιαν 2023 · CREATE UNIQUE INDEX device_serial ON employees (device_serial); Adding the UNIQUE keyword when creating the index instructs the database to ensure that the values in the device_serial column can’t repeat. With unique indexes, all new rows added to the table will be checked against the index to determine whether the column value satisfies the ...
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.
To create a unique index, use the CREATE UNIQUE INDEX statement like this: CREATE UNIQUE INDEX index_name [USING {BTREE | HASH}] ON table_name (column_list) [algorithm_option | lock_option]; Explanation: The UNIQUE keyword indicates that this index is a unique index. index_name is the name of the index.
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.
