Query Execution
... depending on the operation such as an union of two relations which contain duplicates ƒ Components –Variables that stand for relations and Constants which are finite relations –Expressions of relational algebra are referred to as queries ƒ Set Operations on Relations –R u S, the union of R and S (di ...
... depending on the operation such as an union of two relations which contain duplicates ƒ Components –Variables that stand for relations and Constants which are finite relations –Expressions of relational algebra are referred to as queries ƒ Set Operations on Relations –R u S, the union of R and S (di ...
Generic and Declarative Approaches to Data Cleaning
... It is also possible to consider with the schema a referential integrity constraint that requires that every student (number) in the relation Enrollment appears, associated with a student name, in relation Students, the official “table” of students. This is denoted with Enrollement[StuNum] ⊆ Students ...
... It is also possible to consider with the schema a referential integrity constraint that requires that every student (number) in the relation Enrollment appears, associated with a student name, in relation Students, the official “table” of students. This is denoted with Enrollement[StuNum] ⊆ Students ...
SQL – Part II
... – For each sales rep with fewer than four customers, list the rep number, the number of customers assigned to the rep, and the average balance of the rep’s customers. Rename the count of the number of customers and the average of the balances to NumOfCustomers and AverageBalance. – Use of “Having” c ...
... – For each sales rep with fewer than four customers, list the rep number, the number of customers assigned to the rep, and the average balance of the rep’s customers. Rename the count of the number of customers and the average of the balances to NumOfCustomers and AverageBalance. – Use of “Having” c ...
Chapter 3 - Personal Web Pages
... ICs are based upon the semantics of the realworld enterprise that is being described in the database relations. We can check a database instance to see if an IC is violated, but we can NEVER infer that an IC is true by looking at an instance. ...
... ICs are based upon the semantics of the realworld enterprise that is being described in the database relations. We can check a database instance to see if an IC is violated, but we can NEVER infer that an IC is true by looking at an instance. ...
File
... You might think of an RDBMS as an operating system (or set of subsystems), designed specifically for controlling data access; its primary functions are storing, retrieving, and securing data. An RDBMS maintains its own list of authorized users and their associated privileges; manages memory caches a ...
... You might think of an RDBMS as an operating system (or set of subsystems), designed specifically for controlling data access; its primary functions are storing, retrieving, and securing data. An RDBMS maintains its own list of authorized users and their associated privileges; manages memory caches a ...
Spatial Query Languages
... •FROM specifies relevant tables •WHERE specifies qualifying conditions for rows •ORDER BY specifies sorting columns for results •GROUP BY, HAVING specifies aggregation and statistics •Operators and functions •arithmetic operators, e.g. +, -, … •comparison operators, e.g. =, <, >, BETWEEN, LIKE… •log ...
... •FROM specifies relevant tables •WHERE specifies qualifying conditions for rows •ORDER BY specifies sorting columns for results •GROUP BY, HAVING specifies aggregation and statistics •Operators and functions •arithmetic operators, e.g. +, -, … •comparison operators, e.g. =, <, >, BETWEEN, LIKE… •log ...
No Slide Title
... 1. r, s must have the same arity (same number of attributes, same heading) 2. The attribute domains must be compatible (e.g., 2nd column of r deals with the same type of values as does the 2nd column of s) E.g. to find all customers with either an account or a loan customer-name (depositor) cust ...
... 1. r, s must have the same arity (same number of attributes, same heading) 2. The attribute domains must be compatible (e.g., 2nd column of r deals with the same type of values as does the 2nd column of s) E.g. to find all customers with either an account or a loan customer-name (depositor) cust ...
Best Practices for Semantic Data Modeling for
... type. One option is to store it as a SQLVARIANT, another is to place values in data type tables─one name/value pair table for strings, one for floats, and so on. In addition, there must be more metadata available to be used. Can you aggregate the value? SQLVARIANT has not been shown to cause perform ...
... type. One option is to store it as a SQLVARIANT, another is to place values in data type tables─one name/value pair table for strings, one for floats, and so on. In addition, there must be more metadata available to be used. Can you aggregate the value? SQLVARIANT has not been shown to cause perform ...
Outline
... Local area networks (LAN) ➡ Communication cost not that dominant ➡ Total cost function should be considered ➡ Broadcasting can be exploited (joins) ➡ Special algorithms exist for star networks ...
... Local area networks (LAN) ➡ Communication cost not that dominant ➡ Total cost function should be considered ➡ Broadcasting can be exploited (joins) ➡ Special algorithms exist for star networks ...
PPT - Electrical and Computer Engineering Department
... the operation, +, –, , and /, and operating on constants or attributes of tuples. The query: select ID, name, salary/12 from instructor would return a relation that is the same as the instructor relation, except that the value of the attribute salary is divided by 12. ...
... the operation, +, –, , and /, and operating on constants or attributes of tuples. The query: select ID, name, salary/12 from instructor would return a relation that is the same as the instructor relation, except that the value of the attribute salary is divided by 12. ...
Containment of Conjunctive Queries over Databases With Null Values
... For the discussion of boolean queries we introduce some extra notation. For a query q, the substitution that maps every singleton variable of q to ⊥ is denoted as θ⊥ . The corresponding null version θ⊥ Dq is denoted as Dq⊥ . Theorem 2 (Characterization for Boolean Queries). Let q, q 0 be boolean con ...
... For the discussion of boolean queries we introduce some extra notation. For a query q, the substitution that maps every singleton variable of q to ⊥ is denoted as θ⊥ . The corresponding null version θ⊥ Dq is denoted as Dq⊥ . Theorem 2 (Characterization for Boolean Queries). Let q, q 0 be boolean con ...
A Database Perspective on Knowledge Discovery
... Several rule query languages have been proposed so far. In general, rule query languages include two categories: those targeted at propositional rules, such as the rules defined in the previous section, and query languages dealing with predicate rules. In this section we briefly review the main feat ...
... Several rule query languages have been proposed so far. In general, rule query languages include two categories: those targeted at propositional rules, such as the rules defined in the previous section, and query languages dealing with predicate rules. In this section we briefly review the main feat ...
E - Read
... T(branch-name, branch-city, assets, account-number, balance) Push projections using equivalence rules 8a and 8b; eliminate unneeded attributes from intermediate results to get: customer-name ( account-number t(branch-name, branch-city, assets, accountnumber, balance) depositor(customer-name, acc ...
... T(branch-name, branch-city, assets, account-number, balance) Push projections using equivalence rules 8a and 8b; eliminate unneeded attributes from intermediate results to get: customer-name ( account-number t(branch-name, branch-city, assets, accountnumber, balance) depositor(customer-name, acc ...
Lecture 5 ppt - School of Computer Science
... • The
... • The
for a
unique constraint are
a list of columns
which make up the
candidate key
CONSTRAINT
UNIQUE
(col1, col2, …)
...
primary key
... An entity is in first normal form if there are no attributes which can have more than one value for each instance (record) of the entity Attributes which could have more than one value for a given entity belong to a different kind of entity In other words, every attribute appears only once for each ...
... An entity is in first normal form if there are no attributes which can have more than one value for each instance (record) of the entity Attributes which could have more than one value for a given entity belong to a different kind of entity In other words, every attribute appears only once for each ...
Paper
... sequence of self joins on the XASR table. For each location step in the path we have a join operation that connects the current context nodes to the relevant nodes of the next step. The XASR combined with a full text index provides a powerful method to search on (text) contents of nodes. ...
... sequence of self joins on the XASR table. For each location step in the path we have a join operation that connects the current context nodes to the relevant nodes of the next step. The XASR combined with a full text index provides a powerful method to search on (text) contents of nodes. ...
Introduction to Relational Database Management Systems
... A primary key is also required in the Sales table. In addition, the customer number of the customer should also appear in this table as a "field". A field is a single type of information in a table; in the Customers table, we would have a customer name field, a customer number field, etc. The custo ...
... A primary key is also required in the Sales table. In addition, the customer number of the customer should also appear in this table as a "field". A field is a single type of information in a table; in the Customers table, we would have a customer name field, a customer number field, etc. The custo ...
Database-Connection Libraries
... § The first time next() is applied, it gets the first tuple § If there are no more tuples, next() returns the value false ...
... § The first time next() is applied, it gets the first tuple § If there are no more tuples, next() returns the value false ...
