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In computer science, multiple granularity locking (MGL) is a locking method used in database management systems (DBMS) and relational databases. In multiple granularity locking, locks are set on objects that contain other objects. MGL exploits the hierarchical nature of the contains relationship.
The relational algebra uses set union, set difference, and Cartesian product from set theory, and adds additional constraints to these operators to create new ones.. For set union and set difference, the two relations involved must be union-compatible—that is, the two relations must have the same set of attributes.
In database management, an aggregate function or aggregation function is a function where multiple values are processed together to form a single summary statistic. (Figure 1) Entity relationship diagram representation of aggregation. Common aggregate functions include: Average (i.e., arithmetic mean) Count; Maximum; Median; Minimum; Mode ...
Example of QBE query with joins, designed in Borland's Paradox database. Query by Example (QBE) is a database query language for relational databases.It was devised by Moshé M. Zloof at IBM Research during the mid-1970s, in parallel to the development of SQL. [1]
MongoDB can be used as a file system, called GridFS, with load-balancing and data-replication features over multiple machines for storing files. This function, called a grid file system, [36] is included with MongoDB drivers. MongoDB exposes functions for file manipulation and content to developers.
Multiple choice questions lend themselves to the development of objective assessment items, but without author training, questions can be subjective in nature. Because this style of test does not require a teacher to interpret answers, test-takers are graded purely on their selections, creating a lower likelihood of teacher bias in the results. [8]
The information is packaged into aggregate reports and then sold to businesses, as well as to local, state, and government agencies. This information can also be useful for marketing purposes. In the United States, many data brokers' activities fall under the Fair Credit Reporting Act (FCRA) which regulates consumer reporting agencies .
In SQL the UNION clause combines the results of two SQL queries into a single table of all matching rows.The two queries must result in the same number of columns and compatible data types in order to unite.