13 differences between MySQL and Oracle

One 、 concurrency

Concurrency is the most important feature of database , But concurrency involves the acquisition of resources 、 Sharing and locking .

mysql：mysql Mainly table lock , The granularity of resource locking is very large , If one session Locking a watch for too long , Will let others session Unable to update data in this table . although InnoDB The table of the engine can use row level lock , But the mechanism of this row level lock depends on the index of the table , If the table has no index , perhaps sql The statement does not use an index , Then still use table level locks .

oracle：oracle Using row level locks , The granularity of resource locking is much smaller , It's just locking sql Resources needed , And the lock is on the data row in the database , Independent of index . therefore oracle Support for concurrency is much better .

Two 、 Uniformity

mysql：mysql There's nothing like oracle A mechanism for constructing multi version data blocks , Only support read commited Isolation level . One session When reading data , other session Can't change data , But you can insert data at the end of the table .session When updating data , To add an exclusive lock , other session Unable to access data .

oracle：oracle Support serializable Isolation level , The highest level of read consistency can be achieved . Every session Others after submission session To see the submitted changes .oracle By means of undo Construct multi version data blocks in table space to achieve read consistency , Every session When inquiring , If the corresponding data block changes ,oracle Will be in undo For this... In the table space session The old data block when constructing its query .

3、 ... and 、 Business

mysql stay innodb Transactions are only supported when the row level lock of the storage engine .

oracle Fully support affairs very early .

Four 、 Data persistence

mysql： Default submit sql sentence , But if something happens during the update process db Or the host restarts , Data may be lost .

oracle： Ensure that the submitted data can be recovered , because oracle Put the submitted sql The operating line is written to the online log file , Keep it on disk , In case of abnormal restart of database or host , After restart oracle You can rely on online logs , Recover the data submitted by the customer .

5、 ... and 、 submission

mysql The default is auto submit .

oracle The default is not auto submit , It needs to be submitted by the user manually .

6、 ... and 、 Logical backup

mysql Lock data during logical backup , To ensure that the backup data is consistent , Affecting the normal business dml Use .

oracle Do not lock data during logical backup , And the backup data is consistent .

7、 ... and 、 Hot backup

mysql：myisam The engine of , use mysql Self contained mysqlhostcopy Hot standby , You need to add a read lock to the table , influence dml operation .innodb The engine of , It backs up innodb Tables and indexes of , But no backup .frm file . use ibbackup When the backup , There will be a log file to record the data changes during the backup , So you don't have to lock the watch , Do not affect other users to use the database . But this tool is free .innobackup Is a combination of ibbackup A script used , He'll help yeah .frm Backup of files .

oracle Have mature hot standby tools rman, Hot standby , It does not affect users' use of the database . Even if the backed up databases are inconsistent , You can also make consistent replies through archived logs and online redo logs during recovery .

8、 ... and 、sql Statement expansion and flexibility

mysql Yes sql Statement has many very practical and convenient extensions , such as limit function ,insert You can insert multiple rows of data at a time ,select Some management data may not add from.

oracle I feel more stable and traditional in this regard .

Nine 、 Copy

mysql： Replication server configuration is simple , But when there's something wrong with the main warehouse , The plex may lose some data . And you need to manually switch the cluster library to the main library .

oracle： There's traditional data replication, push or pull , Also have dataguard The disaster recovery mechanism of dual or multiple computers , When there is a problem in the main warehouse , You can automatically switch the standby database to the main database , But configuration management is more complex .

Ten 、 Performance diagnostics

mysql There are fewer diagnostic tuning methods , There are mainly slow query logs .

oracle There are various mature performance diagnosis and tuning tools , Can realize a lot of automatic analysis 、 Diagnostic function . such as awr、addm、sqltrace、tkproof etc.

11、 ... and 、 Authority and security

mysql The user of is related to the host , It doesn't make any sense , In addition, the host is easier to be imitated ip There is a chance .

oracle The concept of authority and security is more traditional , The compasses .

Twelve 、 Partitioned tables and partitioned indexes

mysql The partition table is not yet mature and stable .

oracle The function of partition table and partition index is very mature , Can improve user access db Experience .

13、 ... and 、 Management tools

mysql Fewer management tools , stay linux Installation of management tools under , Sometimes you need to install additional packages （phpmyadmin,etc), There is some complexity .

oracle There are many mature command lines 、 The graphical interface 、web Management tools , There are also many third-party management tools , Management is extremely convenient and efficient .