In this example, thedepartment_idcolumn is marked with theMULkey, meaning it has a multiple key. This key enables streamlined management and retrieval of course information based on departmental associations. 6. Conclusion In this article, we explored the various types of MySQL keys and their dis...
C:\WINDOWS\system32>mysql -h localhost -u root -p mysql -e "DESC func;" Enter password: *** +---+---+---+---+---+---+ | Field | Type | Null | Key | Default | Extra | +---+---+---+---+---+---+ | name | char(64) | NO | PRI | | | | ret | tinyin...
SELECT * from tbl_name WHERE primary_key_part1=1和 primary_key_part2=2; 3、eq_ref 对于每个来自于前面的表的行组合,从该表中读取一行。这可能是最好的联接类型,除了const类型。它用在一个索引的所有部分被联接使用并且索引是UNIQUE或PRIMARY KEY。 eq_ref可以用于使用= 操作符比较的带索引的列。比较值...
This action adds a foreign key constraint on the columns "book_id" and "cate_id" of the "newbook_mast" table, referencing the columns "book_id" and "cateid" of the "torder" table. Foreign key constraints ensure referential integrity between related tables, enforcing that values in the f...
• If COLUMN_KEY is MUL, the column is the first column of a nonunique index in which multiple occurrences of a given value are permitted within the column. If more than one of the COLUMN_KEY values applies to a given column of a table, COLUMN_KEY displays the one with the highest...
Produces a key suitable for filesort. More... longlong val_temporal_with_round (enum_field_types type, uint8 dec) Get date or time value in packed longlong format. More... ulonglong val_uint () virtual String * val_str (String *str)=0 vir...
aws_access_key_id aws_secret_access_key aws_session_token Process specified by the credential_process setting from the config file for the specified profile: AccessKeyId SecretAccessKey SessionToken Settings from the config file for the specified profile: aws_access_key_id aws_secret_acc...
第一章:为什么需要需要进行数据库优化 Mysql的架构介绍 Mysql简介 1.是一种关系型数据库 2.是一种关联数据库管理系统,将数据存储在不同的表中,而不是把所有数据放在一个大仓库里面,增加了速度并提高了灵活性 3.开源的,免费的 公司版本是收费的 4.支持大型数据库,可以处理拥有千万条记录的大型数据库 ...
column.\n\nIf more than one of the Key values applies to a given column of a\ntable, Key displays the one with the highest priority, in the order\nPRI, UNI, MUL.\n\nA UNIQUE index may be displayed as PRI if it cannot contain NULL values\nand there is no PRIMARY KEY in the ...
--lines-terminated-byThis option is used with the --tab option and has the same meaning as the corresponding clause for LOAD DATA INFILE --lock-all-tablesLock all tables across all databases --lock-tablesLock all tables before dumping them ...