Mysql storage engine, can use different storage engines for different tables
MyISAM: insert, check the fast speed of blood, but is not supported, so it is suitable for data warehousing, Web, etc.
InnoDB: support, so it is suitable for things databases
Memory: the data is stored in memory
Archive: something unsafe, so it can be used to save the log or something
Each engine careful there are many features available can see
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index
Mysql storage engine, there are two B-tree and Hash
Advantage of the index: the index can be more than one column or row for a specified speed up queries
Or the packet may be reduced execution time sorting clause
The disadvantages of index: much of the memory
When modifications to the table to increase deleted, the corresponding index also need to change
Classification index: separate index and combination index
A separate index refers to the index only one column, but a table can have multiple separate index
The index is a composite index finger on the table to create multiple fields
Full-text indexing: Find all supported values, allowing repeated and null
Create an index: create table in the establishment of
Simply create an index on a column
Check whether the index is successfully created
select_type refers to the type of select such simple queries, sub-queries, the joint inquiry
Table name table query
partitions when partition table needs
The relationship between type table
possible_keys index (optional)
The actual use of the index key
Key_len index length (in bytes)
ref relationship in another table column names
The number of rows is expected to read data line
Extra association operation information
Create a unique index
The default name is the unique index id (default column name)
Create a separate index
Create Composite Index
Create a full-text index: keyword FULLTEXT, can only use the type of varchar char Text
If the table already exists
1. Create an index using the ALTER TABLE
grammar
ALTER TABLE table_name ADD [UNIQUE|FUUTEXT|SPATIAL]
[INDEX|KEY] [index_name] (col_name[length],...) [ASC|DESC]
ALTER TABLE tabletest ADD UNIQUE INDEX (id);
给tabletest对id列添加唯一索引，名字是id，如果要指定名字后边改成这个 UniqueId(id)，意思是添加唯一索引，名字是UniqueId
2.使用CREATE INDEX创建索引
语法
CREATE [UNIQUE|FULLTEXT|SPATIAL] INDEX index_name ON table_name(col_name[length],...)[ASC|DESC]
CREATE UNIQUE INDEX UniqueId ON tabletest(id)
在tabletest上对id列创建唯一索引，名字是UniqueId
删除索引
1.ALTER TABLEF
语法
ALTER TABLE table_name DROP INDEX index_name
2.DROP INDEX
语法
DROP INDEX index_name on table_name
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