Creating FULLTEXT Indexes for Full-Text Search

Summary: in this tutorial, you will learn how to define the full-text index for performing various full-text searches in MySQL.

Before performing a full-text search in a column of a table, you must index its data. MySQL will recreate the full-text index whenever the data of the column changes. In MySQL, the full-text index is a kind of index that has a name FULLTEXT.

MySQL supports indexing and re-indexing data automatically for full-text search enabled columns. MySQL version 5.6 or later allows you to define a full-text index for a column whose data type is CHAR, VARCHAR or TEXT in MyISAM and InnoDB table types.

Notice that MySQL only supported the full-text index for InnoDB tables since version 5.6.

MySQL allows you to define the FULLTEXT index by using the CREATE TABLEstatement when you create the table or ALTER TABLE or CREATE INDEX statement for the existing tables.

Create FULLTEXT index using CREATE TABLE statement

Typically, you define the FULLTEXT index for a column when you create a new table using the CREATE TABLE statement as follows:

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CREATE TABLE table_name(     column_list,     ...,     FULLTEXT (column1,column2,..) );

To create the FULLTEXT index, you place a list of comma-separated column names in parentheses after the FULLTEXT keyword.

The following statement creates a new table named posts that has a FULLTEXT index that includes the post_content column.

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CREATE TABLE posts (   id INT NOT NULL AUTO_INCREMENT,   title VARCHAR(255) NOT NULL,   body TEXT,   PRIMARY KEY (id),   FULLTEXT KEY (body ) );

Create FULLTEXT index using ALTER TABLE statement

The following syntax defines a FULLTEXT index using the ALTER TABLE statement:

1 2	ALTER TABLE table_name   ADD FULLTEXT(column_name1, column_name2,…)

In this syntax,

• First, specify the name of the table that you want to create the index after the ALTER TABLE keywords.
• Second, use the ADD FULLTEXT clause to define the FULLTEXT index for one or more columns of the table.

For example, you can define a FULLTEXT index for the productDescription and productLine columns in the products table of the sample database as follows:

1 2	ALTER TABLE products   ADD FULLTEXT(productDescription,productLine)

Create FULLTEXT index using CREATE INDEX statement

You can also use the CREATE INDEX statement to create a FULLTEXT index for existing tables using the following syntax:

1 2	CREATE FULLTEXT INDEX index_name ON table_name(idx_column_name,...)

For example, the following statement creates a FULLTEXT index for the addressLine1 and addressLine2 columns of the offices table:

1 2	CREATE FULLTEXT INDEX address ON offices(addressLine1,addressLine2)

Notice that for a table which has many rows, it is faster to load the data into the table that has no FULLTEXT index first and then create the FULLTEXT index, than loading a large amount of data into a table that has an existing FULLTEXT index.

Drop a FULLTEXT index

To drop a FULLTEXT index, you use the ALTER TABLE DROP INDEX statement.

1 2	ALTER TABLE table_name DROP INDEX index_name;

For example, the following statement removes the address index from the offices table:

1 2	ALTER TABLE offices DROP INDEX address;

In this tutorial, you have shown you how to create FULLTEXT indexes that support full-text search in MySQL.