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This article is mainly about the type and function of MySQL index, if you are interested, let's take a look at this article. I believe it is of some reference value to you after reading the type and function of MySQL index.

For some large websites, the role of index is very obvious, the establishment of MySQL index is very important for the efficient operation of MySQL, index can greatly improve the retrieval speed of MySQL. 1. General index this is the most basic index, it does not have any restrictions to increase the index CREATE INDEX indexName ON student (username); modify the index ALTER table tableName ADD INDEX student (username) delete the index DROP INDEX [indexName] ON student; 2, the unique index it is similar to the previous ordinary index, except that the value of the index column must be unique, but null values are allowed. If it is a combined index, the combination of column values must be unique. It can be created in the following ways: CREATE UNIQUE INDEX indexName ON student (username) ALTER table studen ADD UNIQUE [indexName] (username (length)) 3, primary key index ALTER TABLE tbl_name ADD PRIMARY KEY (userid) 4, full-text index ALTER TABLE tbl_name ADD FULLTEXT index_name (username)

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