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This article mainly introduces the mysql to check whether there is an index method, has a certain reference value, friends in need can refer to. I hope you will learn a lot after reading this article. Next, let the editor take you to learn about it.

In mysql, you can use SQL's "SHOW INDEX" statement to check whether there is an index in the data table, the syntax format "SHOW INDEX FROM [FROM]"; return a series of index information in the data table, such as the name of the index, the column fields that define the index, and so on.

In MySQL, you can use the SHOW INDEX statement to view the indexes created in the table.

The syntax format for viewing the index is as follows:

SHOW INDEX FROM [FROM]

The syntax is as follows:

Specifies the name of the data table to view the index

Specifies the database in which the data table to view the index is located, which can be omitted For example, the SHOW INDEX FROM student FROM test; statement means to view the index of the student data table in the test database.

Example:

The main parameters are described as follows:

The parameter description Table represents the name of the data table in which the index was created, in this case the tb_stu_info2 data table. Non_unique indicates whether the index is unique. If it is not a unique index, the value of the column is 1; if it is a unique index, the value of the column is 0. Key_name represents the name of the index. Seq_in_index represents the position of the column in the index, and if the index is single, the value of the column is 1; if the index is a composite index, the value of the column is the order of each column in the index definition. Column_name represents the column field that defines the index. Collation indicates the order in which columns are stored in the index. In MySQL, ascending order displays the value "A" (ascending order), and if shown as NULL, there is no classification. An estimate of the number of unique values in the Cardinality index. The cardinality is counted according to the statistics stored as integers, so even for small tables, the value does not have to be accurate. The higher the cardinality, the greater the chance that MySQL will use the index when federating. Sub_part represents the number of characters indexed in the column. If the column is only partially indexed, the value of the column is the number of characters indexed; if the entire column is indexed, the value of the column is NULL. Packed indicates how keywords are compressed. If not compressed, the value is NULL. Null is used to show whether the index column contains NULL. If the column contains NULL, the value of the column is YES. If not, the value of the column is NO. Index_type displays the types and methods used by the index (BTREE, FULLTEXT, HASH, RTREE). Comment displays comments. Thank you for reading this article carefully. I hope the editor will share mysql to see if there is any indexing method and content will be helpful to everyone. At the same time, I also hope that you will support us, pay attention to the industry information channel, and find out if you encounter problems. Detailed solutions are waiting for you to learn!

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