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In computer science, the count-distinct problem [1] (also known in applied mathematics as the cardinality estimation problem) is the problem of finding the number of distinct elements in a data stream with repeated elements. This is a well-known problem with numerous applications.
One-to-many: order ←→ line item: 1: 1..* or + An order contains at least one item Many-to-one: person ←→ birthplace: 1..* or + 1: Many people can be born in the same place, but 1 person can only be born in 1 birthplace Many-to-many: course ←→ student: 1..* or + 1..* or + Students follow various courses Many-to-many (optional on both ...
A snippet of Python code with keywords highlighted in bold yellow font. The syntax of the Python programming language is the set of rules that defines how a Python program will be written and interpreted (by both the runtime system and by human readers). The Python language has many similarities to Perl, C, and Java. However, there are some ...
For example, take a car and an owner of the car. The car can only be owned by one owner at a time or not owned at all, and an owner could own zero, one, or multiple cars. One owner could have many cars, one-to-many. In a relational database, a one-to-many relationship exists when one record is related to many records of another table. A one-to ...
For example, think of A as Authors, and B as Books. An Author can write several Books, and a Book can be written by several Authors. In a relational database management system, such relationships are usually implemented by means of an associative table (also known as join table, junction table or cross-reference table), say, AB with two one-to-many relationships A → AB and B → AB.
In the given example, there are 12 = 2(3!) permutations with property P 1, 6 = 3! permutations with property P 2 and no permutations have properties P 3 or P 4 as there are no restrictions for these two elements. The number of permutations satisfying the restrictions is thus: 4! − (12 + 6 + 0 + 0) + (4) = 24 − 18 + 4 = 10.
Cardinality bounds can be used in the body of a rule as well, for instance: :- 2 { p , q , r }. Adding this constraint to an Lparse program eliminates the stable models that contain at least 2 of the atoms p , q , r {\displaystyle p,q,r} .
CPython is distributed with a large standard library written in a mixture of C and native Python, and is available for many platforms, including Windows (starting with Python 3.9, the Python installer deliberately fails to install on Windows 7 and 8; [141] [142] Windows XP was supported until Python 3.5) and most modern Unix-like systems ...