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The typical situation that will make a SQL query non-sargable is to include in the WHERE clause a function operating on a column value. The WHERE clause is not the only clause where sargability can matter; it can also have an effect on ORDER BY, GROUP BY and HAVING clauses.
If the field we arrived at was E(0, y 1), then T[y 1 + 1] ... T[y 2] is a substring of T with the minimal edit distance to the pattern P. Computing the E(x, y) array takes O(mn) time with the dynamic programming algorithm, while the backwards-working phase takes O(n + m) time. Another recent idea is the similarity join.
A simple and inefficient way to see where one string occurs inside another is to check at each index, one by one. First, we see if there is a copy of the needle starting at the first character of the haystack; if not, we look to see if there's a copy of the needle starting at the second character of the haystack, and so forth.
The picture shows two strings where the problem has multiple solutions. Although the substring occurrences always overlap, it is impossible to obtain a longer common substring by "uniting" them. The strings "ABABC", "BABCA" and "ABCBA" have only one longest common substring, viz. "ABC" of length 3.
Suppose for a given alignment of P and T, a substring t of T matches a suffix of P and suppose t is the largest such substring for the given alignment. Then find, if it exists, the right-most copy t ′ of t in P such that t ′ is not a suffix of P and the character to the left of t ′ in P differs from the character to the left of t in P.
Oracle and IBM Db2 provide a construct explicitly named CLOB, [1] [2] and the majority of other database systems support some form of the concept, often labeled as text, memo or long character fields. CLOBs usually have very high size-limits, of the order of gigabytes. The tradeoff for the capacity is usually limited access methods.
The bitap algorithm (also known as the shift-or, shift-and or Baeza-Yates-Gonnet algorithm) is an approximate string matching algorithm. The algorithm tells whether a given text contains a substring which is "approximately equal" to a given pattern, where approximate equality is defined in terms of Levenshtein distance – if the substring and pattern are within a given distance k of each ...
contains(string,substring) returns boolean Description Returns whether string contains substring as a substring. This is equivalent to using Find and then detecting that it does not result in the failure condition listed in the third column of the Find section. However, some languages have a simpler way of expressing this test.