In the ideal gas law equation, what does the variable n stands for B. moles of gas. (n: a lowercase ânâ stands for the number of moles of a gas. [ This is a measurement in moles, so if you are given a mass in grams or kilograms, be sure to change it to moles first.) ]. Expert answered| cecillereign |Points 261|.
Theta-Join I The theta-join of two relations R and S is the set of tuples in theCartesian product of R and S that satisfy some condition C.RA R ./ C SSQL SELECT *FROM R, SWHERE C; I R ./ C S = Ë C (R S): T. M. Murali August 30, 2010 CS4604: SQL and Relational Algebra. Results of operations are also sets of tuples. (Later, we will dene arelational algebra on bags.) I Think of expressions in relational algebra as queries, which construct newrelations from given relations. I Four types of operators: I Remove parts of a single relation: projection and selection.
Why? 1  Similar to normal algebra (as in. ), 2  except we use relations as values instead of numbers, and the operations and operators are different. 3  Not used as a query language in actual DBMSs. 4  The inner, lower-level operations of a relational DBMS are, or are similar to, relational algebra operations. 5  Some advanced SQL queries requires explicit 6  ... Re Inside a relational DBMS, it is usually much more efficient to calculate a join directly, instead of calculating a cartesian product and then throwing away most of the lines. 2  Note that the same SQL query can be translated to several different relational algebra expressions, which all give the same result.