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In SQL, the unique keys have a UNIQUE constraint assigned to them in order to prevent duplicates (a duplicate entry is not valid in a unique column). Alternate keys may be used like the primary key when doing a single-table select or when filtering in a where clause, but are not typically used to join multiple tables.
PostgreSQL has a distinct BOOLEAN type as in the standard, [21] which allows predicates to be stored directly into a BOOLEAN column, and allows using a BOOLEAN column directly as a predicate in a WHERE clause. In MySQL, BOOLEAN is treated as an alias of TINYINT (1); [22] TRUE is the same as integer 1 and FALSE is the same is integer 0. [23]
The standard pow function and the integer exponent pown function define 0 0, 1 ∞, and ∞ 0 as 1. The powr function defines all three indeterminate forms as invalid operations and so returns NaN. Real operations with complex results, for example: The square root of a negative number. The logarithm of a negative number.
Euler's totient or phi function, φ(n) is an arithmetic function that counts the number of positive integers less than or equal to n that are relatively prime to n. That is, if n is a positive integer , then φ( n ) is the number of integers k in the range 1 ≤ k ≤ n which have no common factor with n other than 1.
In statistics, ordinary least squares (OLS) is a type of linear least squares method for choosing the unknown parameters in a linear regression model (with fixed level-one [clarification needed] effects of a linear function of a set of explanatory variables) by the principle of least squares: minimizing the sum of the squares of the differences between the observed dependent variable (values ...
Data envelopment analysis provides efficiency coefficients similar to those obtained by multivariate analysis without any distributional assumption. KNNs classify the unseen instance based on the K points in the training set which are nearest to it. A support vector machine (with a Gaussian kernel) is a nonparametric large-margin classifier.
The number of unique journeys on the metro system every year. There is a major discrepancy between the ridership figures: some metro systems count transferring between lines as multiple journeys, but others do not.
The procedure for the ADF test is the same as for the Dickey–Fuller test but it is applied to the model = + + + + + + +, where is a constant, the coefficient on a time trend and the lag order of the autoregressive process.