MySQL add and delete indexes

Index type ： General index , unique index , Full-text index , Spatial index

1、 General index

NORMAL： This is the most basic index , It has no restrictions , For example, the above is title The index created by a field is a normal index ,MyIASM In the default BTREE Index of type , It's also the index we use most of the time .

1、 Create index

CREATE INDEX indexName ON runoob_tbl (runoob_title);

2、 Modify table structure ( Add index )

See table details

desc runoob_tbl;

runoob_tbl： The name of the table
INDEX： Normal index type
indexName： The index name
runoob_title： Set the index field

ALTER TABLE runoob_tbl ADD INDEX indexName (runoob_title);

And then through navicat Software view index , Added a name ：indexName The general index of , Field name ：runoob_title

3、 Delete index （ It's the same operation ）

When deleting an index, you must remember the name of the index

ALTER TABLE runoob_tbl drop INDEX indexName

2、 unique index

UNIQUE： Similar to a normal index , The difference is that ： The value of the index column must be unique , But you can have an empty value （ Note that it's different from the primary key ）. If it's a composite index , The combination of column values must be unique , The creation method is similar to a normal index

1. Create unique index

CREATE UNIQUE INDEX indexName ON runoob_tbl(runoob_title) 

2、 Modify table structure

ALTER table runoob_tbl ADD UNIQUE [indexName] (runoob_title)

3、 Full-text index

FULLTEXT：,FULLTEXT The index can only be used for MyISAM surface ; They can learn from CHAR、VARCHAR or TEXT Column as CREATE TABLE Part of the statement is created , Or use it later ALTER TABLE or CREATE INDEX Be added . For larger datasets , Enter your data into one without FULLTEXT In the indexed table , Then create the index , It's faster than inputting data into existing FULLTEXT Indexing is faster . But remember for large data tables , Generating full-text index is a very time-consuming and hard disk space consuming approach .

4、 Spatial index

SPATIAL： Represents the data type of spatial value , Functions that manipulate space values , Spatial index , Used to provide the speed of accessing spatial columns