show index from table_name;show keys from table_name;

-- index_name可以省略, 创建普通索引ALTER TABLE table_name ADD INDEX index_name (column_list，column_list2 )
-- 创建唯一索引ALTER TABLE table_name ADD UNIQUE (column_list)
-- 创建主键索引ALTER TABLE table_name ADD PRIMARY KEY (column_list)

--或则是以下两种，只能作用于普通索引和唯一索引CREATE INDEX index_name ON 
table_name (column_list)CREATE UNIQUE INDEX index_name ON table_name (column_list)

DROP INDEX index_name ON table_nameALTER TABLE table_name DROP INDEX index_nameALTER TABLE 
table_name DROP PRIMARY KEY