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What is the precision of a number in SQL Server?
Precision is the number of digits in a number. Scale is the number of digits to the right of the decimal point in a number. For example, the number 123.45 has a precision of 5 and a scale of 2. In SQL Server, the default maximum precision of numeric and decimal data types is 38. In earlier versions of SQL Server, the default maximum is 28.
Which is the correct formula for precision recall?
Precision ( P) is defined as the number of true positives ( T p ) over the number of true positives plus the number of false positives ( F p ). Recall ( R) is defined as the number of true positives ( T p ) over the number of true positives plus the number of false negatives ( F n ).
Recall ( R) is defined as the number of true positives ( T p ) over the number of true positives plus the number of false negatives ( F n ). These quantities are also related to the ( F 1) score, which is defined as the harmonic mean of precision and recall. Note that the precision may not decrease with recall.
Can a system have high precision but low recall?
A system with high recall but low precision returns many results, but most of its predicted labels are incorrect when compared to the training labels. A system with high precision but low recall is just the opposite, returning very few results, but most of its predicted labels are correct when compared to the training labels.
Can you query a table without an ORDER BY clause?
But actually in SQL Server and Oracle (I’ve tested on those 2 platforms), if I query from a table without an order by clause multiple times, I always get the results in the same order. Does this behavior can be relied on? Anyone can help to explain a little? No, that behavior cannot be relied on.
Why does the order change between two SQL queries?
The order could even change between two identical queries just because of data that has changed between those queries. a “where” clause may be satisfied with an index scan in one query, but later inserts could make that condition less selective, and the planner could decide to perform a subsequent query using a table scan.
What happens when precision is greater than 38?
When a result precision is greater than 38, it’s reduced to 38, and the corresponding scale is reduced to try to prevent truncating the integral part of a result. In some cases such as multiplication or division, scale factor won’t be reduced, to maintain decimal precision, although the overflow error can be raised.
How is the second Union processed in SQL?
The second UNION is processed first because it’s in parentheses, and returns 5 rows because the ALL option isn’t used and the duplicates are removed. These 5 rows are combined with the results of the first SELECT by using the UNION ALL keywords. This example doesn’t remove the duplicates between the two sets of five rows.
When to use Union of two SELECT statements?
When any SELECT statement in a UNION statement includes an ORDER BY clause, that clause should be placed after all SELECT statements. The following example shows the incorrect and correct use of UNION in two SELECT statements in which a column is ordered with ORDER BY. G. Using UNION of two SELECT statements with WHERE and ORDER BY