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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. 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.
To create an index for a column or a list of columns, you specify the index name, the table to which the index belongs, and the column list. For example, to add a new index for the column c4, you use the following statement: CREATE INDEX idx_c4 ON t(c4); Code language: SQL (Structured Query Language) (sql)
27 cze 2024 · The MySQL CREATE INDEX statement is a DDL (Data Definition Language) statement used to create indexes on tables. It allows developers to optimize query performance by specifying which columns should be indexed.
Creating indexes – introduce the index concept and show you how to create an index for one or more columns of a table. Removing indexes – show you how to remove an existing index of a table. Listing table indexes – provide you with a statement to list all indexes or specific indexes of a table.
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.
4 sty 2023 · CREATE INDEX names ON employees (last_name, first_name); In this case, the CREATE INDEX statement differs slightly. Now in the parentheses after the table name (employees), two columns are listed: last_name and then first_name. This creates a multi-column index on both columns.
The CREATE INDEX statement is a fundamental SQL command used in MySQL databases to create indexes on tables. Indexes are data structures that help MySQL retrieve data from tables more efficiently. They are essentially pointers or lookup tables that store the location of specific rows in a table based on certain columns.
