深刻淺析SQL封裝、多態與重載。本站提示廣大學習愛好者：（深刻淺析SQL封裝、多態與重載）文章只能為提供參考，不一定能成為您想要的結果。以下是深刻淺析SQL封裝、多態與重載正文
裝置MySQL時，有warning:
[root@localhost mysql]# scripts/mysql_install_db --user=mysql Installing MySQL system tables...2015-08-13 14:20:09 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details). 2015-08-13 14:20:09 0 [Note] ./bin/mysqld (mysqld 5.6.26) starting as process 1934 ... 2015-08-13 14:20:09 1934 [Note] InnoDB: Using mutexes to ref count buffer pool pages 2015-08-13 14:20:09 1934 [Note] InnoDB: The InnoDB memory heap is disabled 2015-08-13 14:20:09 1934 [Note] InnoDB: Mutexes and rw_locks use InnoDB's own implementation 2015-08-13 14:20:09 1934 [Note] InnoDB: Memory barrier is not used 2015-08-13 14:20:09 1934 [Note] InnoDB: Compressed tables use zlib 1.2.3 2015-08-13 14:20:09 1934 [Note] InnoDB: Using Linux native AIO 2015-08-13 14:20:09 1934 [Note] InnoDB: Not using CPU crc32 instructions 2015-08-13 14:20:09 1934 [Note] InnoDB: Initializing buffer pool, size = 128.0M 2015-08-13 14:20:09 1934 [Note] InnoDB: Completed initialization of buffer pool 2015-08-13 14:20:10 1934 [Note] InnoDB: The first specified data file ./ibdata1 did not exist: a new database to be created! 2015-08-13 14:20:10 1934 [Note] InnoDB: Setting file ./ibdata1 size to 12 MB 2015-08-13 14:20:10 1934 [Note] InnoDB: Database physically writes the file full: wait... 2015-08-13 14:20:10 1934 [Note] InnoDB: Setting log file ./ib_logfile101 size to 48 MB 2015-08-13 14:20:11 1934 [Note] InnoDB: Setting log file ./ib_logfile1 size to 48 MB 2015-08-13 14:20:12 1934 [Note] InnoDB: Renaming log file ./ib_logfile101 to ./ib_logfile0 2015-08-13 14:20:12 1934 [Warning] InnoDB: New log files created, LSN=45781 2015-08-13 14:20:12 1934 [Note] InnoDB: Doublewrite buffer not found: creating new 2015-08-13 14:20:12 1934 [Note] InnoDB: Doublewrite buffer created 2015-08-13 14:20:12 1934 [Note] InnoDB: 128 rollback segment(s) are active. 2015-08-13 14:20:12 1934 [Warning] InnoDB: Creating foreign key constraint system tables. 2015-08-13 14:20:12 1934 [Note] InnoDB: Foreign key constraint system tables created 2015-08-13 14:20:12 1934 [Note] InnoDB: Creating tablespace and datafile system tables. 2015-08-13 14:20:12 1934 [Note] InnoDB: Tablespace and datafile system tables created. 2015-08-13 14:20:12 1934 [Note] InnoDB: Waiting for purge to start 2015-08-13 14:20:12 1934 [Note] InnoDB: 5.6.26 started; log sequence number 0 2015-08-13 14:20:14 1934 [Note] Binlog end 2015-08-13 14:20:14 1934 [Note] InnoDB: FTS optimize thread exiting. 2015-08-13 14:20:14 1934 [Note] InnoDB: Starting shutdown... 2015-08-13 14:20:16 1934 [Note] InnoDB: Shutdown completed; log sequence number 1625977
OK
Filling help tables...2015-08-13 14:20:16 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details). 2015-08-13 14:20:16 0 [Note] ./bin/mysqld (mysqld 5.6.26) starting as process 1957 ... 2015-08-13 14:20:16 1957 [Note] InnoDB: Using mutexes to ref count buffer pool pages 2015-08-13 14:20:16 1957 [Note] InnoDB: The InnoDB memory heap is disabled 2015-08-13 14:20:16 1957 [Note] InnoDB: Mutexes and rw_locks use InnoDB's own implementation 2015-08-13 14:20:16 1957 [Note] InnoDB: Memory barrier is not used 2015-08-13 14:20:16 1957 [Note] InnoDB: Compressed tables use zlib 1.2.3 2015-08-13 14:20:16 1957 [Note] InnoDB: Using Linux native AIO 2015-08-13 14:20:16 1957 [Note] InnoDB: Not using CPU crc32 instructions 2015-08-13 14:20:16 1957 [Note] InnoDB: Initializing buffer pool, size = 128.0M 2015-08-13 14:20:16 1957 [Note] InnoDB: Completed initialization of buffer pool 2015-08-13 14:20:16 1957 [Note] InnoDB: Highest supported file format is Barracuda. 2015-08-13 14:20:16 1957 [Note] InnoDB: 128 rollback segment(s) are active. 2015-08-13 14:20:16 1957 [Note] InnoDB: Waiting for purge to start 2015-08-13 14:20:16 1957 [Note] InnoDB: 5.6.26 started; log sequence number 1625977 2015-08-13 14:20:17 1957 [Note] Binlog end 2015-08-13 14:20:17 1957 [Note] InnoDB: FTS optimize thread exiting. 2015-08-13 14:20:17 1957 [Note] InnoDB: Starting shutdown... 2015-08-13 14:20:18 1957 [Note] InnoDB: Shutdown completed; log sequence number 1625987
OK
To start mysqld at boot time you have to copy support-files/mysql.server to the right place for your system PLEASE REMEMBER TO SET A PASSWORD FOR THE MySQL root USER ! To do so, start the server, then issue the following commands: ./bin/mysqladmin -u root password 'new-password' ./bin/mysqladmin -u root -h localhost.localdomain password 'new-password' Alternatively you can run: ./bin/mysql_secure_installation which will also give you the option of removing the test databases and anonymous user created by default. This is strongly recommended for production servers. See the manual for more instructions. You can start the MySQL daemon with: cd . ; ./bin/mysqld_safe & You can test the MySQL daemon with mysql-test-run.pl cd mysql-test ; perl mysql-test-run.pl Please report any problems at http://bugs.mysql.com/ The latest information about MySQL is available on the web at http://www.mysql.com Support MySQL by buying support/licenses at http://shop.mysql.com New default config file was created as ./my.cnf and will be used by default by the server when you start it. You may edit this file to change server settings WARNING: Default config file /etc/my.cnf exists on the system This file will be read by default by the MySQL server If you do not want to use this, either remove it, or use the --defaults-file argument to mysqld_safe when starting the server [root@localhost mysql]#
[Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
其緣由是從 5.6開端，timestamp 的默許行動曾經是 deprecated 了。
在MySQL 5.6.6之前，TIMESTAMP的默許行動：
TIMESTAMP列假如沒有明白聲明NULL屬性，默許為NOT NULL。（而其他數據類型，假如沒有顯示聲明為NOT NULL，則許可NULL值。）設置TIMESTAMP的列值為NULL，會主動存儲為以後timestamp。
表中的第一個TIMESTAMP列，假如沒有聲明NULL屬性、DEFAULT或許 ON UPDATE，會主動分派 DEFAULT CURRENT_TIMESTAMP和ON UPDATE CURRENT_TIMESTAMP 屬性。
表中第二個TIMESTAMP列，假如沒有聲明為NULL或許DEFAULT子句，默許主動分派'0000-00-00 00:00:00′。拔出行時沒有指明改列的值，該列默許分派'0000-00-00 00:00:00′，且沒有正告。
要封閉正告，須要參加上面的參數：
explicit_defaults_for_timestamp=true
重啟MySQL後毛病消逝，這時候TIMESTAMP的行動以下：
TIMESTAMP假如沒有顯示聲明NOT NULL，是許可NULL值的，可以直接設置改列為NULL，而沒有默許填充行動。
TIMESTAMP不會默許分派DEFAULT CURRENT_TIMESTAMP 和 ON UPDATE CURRENT_TIMESTAMP屬性。
聲明為NOT NULL且沒有默許子句的TIMESTAMP列是沒有默許值的。往數據表中拔出列，又沒有給TIMESTAMP列賦值時，假如是嚴厲SQL形式，會拋出一 個毛病，假如嚴厲SQL形式沒有啟用，該列會賦值為'0000-00-00 00:00:00′，同時湧現一個正告。（這和MySQL處置其他時光類型數據一樣，如DATETIME）
（拜見：http://www.jb51.net/article/71107.htm）
也就是 explicit_defaults_for_timestamp 封閉了 timestamp 類型字段鎖具有的一些會讓人覺得奇異的默許行動，參加了該參數以後，假如還須要為 timestamp類型的字段指定默許行動，那末就須要顯示的在創立表時顯示的指定。explicit_defaults_for_timestamp 也就是這個意思：顯示指定默許值為timestamp類型的字段。
