Search formulas usually consist of search terms and various logical operators. Specifically, it is a search command that can be recognized and executed by a computer, which is formed by connecting the logical relationship and positional relationship between search words with various operators specified by the search system. The quality of retrieval structure is related to the success or failure of retrieval strategy.
The expression structure (*) in common retrieval represents any string. %: Represents one or more arbitrary strings. For example, "China people%" and "Daily News%" have found infinite words that start with "China people" and end with "Daily News" respectively.
Construction of expression in extended data combination retrieval:?
Time: The common formats are: "1990 102", "1999, 0 1 02", "1999/0102". You can use to define the time quota, and you can use "?" , """expression, the query is the author or publishing agency of the article. ?
Keywords: "?" , """expression. ?
Topic: Can you use "?" , """expression. ?
Text: You can use "?" , """expression. ? Free words, also known as arbitrary words, can be randomly selected words and a natural sentence. Some databases can use natural sentences (that is, ask questions), but the system background will automatically extract keywords for the sentences.
Baidu Encyclopedia-Search Expression