nosql databases vs relational databases

July 14, IBM Software group released its newest generation of database products DB2 9, different from other databases, this product combines the advantages of hierarchical database and relational database, can store data in XML format, the status of XML in this database product is no longer subordinate, but one of the core, The resulting series of problems is like stirring up too much spray on a calm surfac

Label:This article is translated from Coding-geek article: How does a relational the database work. Original link: http://coding-geek.com/how-databases-work/#Buffer-replacement_strategies Immediately after the previous article, this article translated the following chapters: One, Log Manager (journal manager)From the previous chapters, we already know that in order to improve performance, the databas

. "Relationship" is an example of a "relational schema" that you can interpret as a table with data, and "relational mode" is the table structure of this datasheet. 1NF is defined as: each attribute in a relationship that conforms to 1NF cannot be divided. The situation shown in table 1 does not meet the requirements of the 1NF. Table 1 In fact, 1NF is the most basic requirement of all

The construction of the database must follow certain rules. In a relational database, this rule is a paradigm. A paradigm is a collection of relational patterns that conform to a certain level. Relationships in relational databases must meet certain requirements, that is, to satisfy different paradigms. There are six t

administrator. The use command is then used to switch to the target database, and the Db.createuser () command is used to create the user with the role name "ReadWrite".There are two types of common database user roles, read and ReadWrite. As the name implies, the former can only read data cannot be modified, the latter may read and modify.Here is an example:> Use testSwitched to DB test> Db.createuser ({User: "TestUser", pwd: "Testpass", roles:["ReadWrite"]})Successfully added User: {"user": "

intent lock is compatible with other locks that are lower than it. Batch update lock Batch update locks on a table allow multiple batches to load threads, load data into tables, and disallow other types of data access. Batch update locks are issued when table locking is enabled on a table, or when the table lock option is selected with a batch operation. Key Range Lock When using serializable isolation levels, key-range locks protect a range of rows that are implied in the result set and are no

performance of the system and various database management operations, including the followingComputing performance of--oracle database--Performance of database access operations--performance of backup and operation4. Create and open a databaseUsing DBCA5. Backing Up the databaseManufacturers have integrated, but need seamless backup recovery must be optimized for processing6. Registering Database UsersCreate users, assign permissions and roles7. Implementing Database DesignCreate table spaces t

operation can be combined into an SQL statement. Take a look at the revised code: $model = new Model (); $result = mysql_query ("UPDATE goods SET quantity = quantity-1 WHERE id = 1"); Because the relational database is stored in a file, modifications to the same record cannot be made concurrently. This means that even if A and B users buy at the same time, the inventory changes are in order, so the inventory can be correctly reduced. There is also

characteristics are suitable for use with serialization isolation (serializable isolation):1, the data volume is large, but the transaction is short, only will update the database with less data rows2, two concurrent transactions the probability of modifying the same data is small3. A transaction with a relatively long run time only performs read-only operationsThis paragraph I see not quite understand, one is the transaction level of the read consistency, one is the sentence level of read cons

Tags: and EXT structure Publishing NAT process name Data Model operationsThe SQL (Structured Query Language) database is the primary way to store data over the past 40 years. The late 1990s with the rise of Web applications and open-source databases such as MySQL, PostgreSQL, and SQLite, the explosion of user growth. NoSQL databases have been in existence since t

Label:In the past, we only needed to learn and use a database technology to do almost all of the database application development. Because the mature and stable relational database products are not many, and for you to choose the free version is even less, so the Internet domain basically chose the free MySQL database. In the rapid development of the WEB2.0 era, we found that the relational database in perf

NoSQL systems generally advertise a feature, that is, good performance. Why? After so many years of development in relational databases, various optimizations have been done very deeply. NoSQL systems generally use relational database technology. What factors have bound the

large-scale SNS website, the daily user generates a huge amount of user dynamics, taking foreign friendfeed as an example, one months to reach 250 million user dynamics, for the relational database, in a 250 million records of the surface of the SQL query, the efficiency is extremely low even intolerable. 3. High Scalability hi availability-requirements for database scalability and high availability Currently Sina Weibo's Redis and Google's BigTable

relative to the transaction (acid, which is the abbreviation for the four basic elements that the database transaction performs correctly. Contains: atomicity (atomicity), consistency (consistency), isolation (isolation), persistence (durability). ), the NoSQL database guarantees the base feature. Base is the final consistency and soft transaction.NoSQL databases do not have a unified architecture, the dif

I. Relational database ( SQL):Mysql,Oraclefeatures : There is a relationship between data and data , between Tables and fields , between tables and tablesFor example : Department table 001 section, Employee table 001User table , user name , passwordClassification Table and commodity tables , one -to-many relationships. Advantages :There is a relationship between ① data, it is very convenient to make and delete data.②

read consistency, rollback segment mechanism are all important mechanisms to ensure read consistency. Isolation: As for isolation, the book says that "when different transactions operate on the same data, each transaction has its own working space". I understand that when different times come to operate the same data, only one transaction is exclusive, and the other transaction can only wait for the exclusive transaction to execute commit or rollback. Later, I thought, the author called the "

method is not not possible, but in the actual use of each time repeated table structure changes is very painful. You can also preset a large number of pre-fields, but in this case, it is easy to get rid of the corresponding state of the field and data, that is, which field holds the data.--the processing of a simple query that requires a quick return of results ("simple" here refers to the absence of complex query conditions)This is not a disadvantage, but in any case, the

Advantages and disadvantages of relational databaseAdvantages: Can do transaction processing, so as to ensure the consistency of data; Can be a join, such as multi-table query; Because of SQL standardization, the cost of data updates is small (the same fields are basically only one place). Disadvantages: The write processing of large amount of data is not easy; If the table data volume is too large, it is not easy to do index or

NoSQL (not-only SQL) non-relational databasecomparison between relational database and non-relational database :Common relational databases: MySQL, Oracle, SQL ServerA relational databa

Label:1. Relational databaseRepository for permanent data storagePHP variables are only temporary storage space "use memory space" to save variables during PHP script execution.Relational database: Use the relationship between the two to describe the entity information. "Using two-dimensional table field names and fields values to describe""Relational databases a