Add index to table in MySQL database

First, add index

1. ALTER TABLE TableName Add index IndexName (conlum1,conlum2)

2. Create index IndexName on TableName (conlum1,conlum2)

Second, delete index

1, ALTER TABLE tableName DROP INDEX indexname;

2, DROP index indexname on tableName;

Third, query the index on table

Show index from TableName

Note: When the data type of the column is varchar and the data is numeric, keep in mind that the data type is consistent; add explain to view query information before select

EXPLAIN SELECT * from xln_source where gender = 9 and age = 3

Key indicates the name of the index used

Add index to table in MySQL database