Three ways of creating indexes in MySQL

1、 Use CREATE INDEX establish , The grammar is as follows ：

CREATEINDEXindexNameONtableName(columnName(length));

2、 Use ALTER Sentence creation , The grammar is as follows ：

ALTERTABLEtableNameADDINDEXindexName(columnName);

ALTER Statement to create an index , The following provides an example of setting the index length ：

ALTERTABLEt_user_action_logADDINDEXip_address_idx(ip_address(16));

SHOWINDEXFROMt_user_action_log;

3、 Create an index when creating a table

CREATETABLEtableName(
idINTNOTNULL,
columnNamecolumnType,
INDEX[indexName](columnName(length))
);

Example ：