Programming/xml2019. 9. 29. 23:03

boolean() 으로 특정 element를 조회하면 될 듯?

 

[링크 : https://stackoverflow.com/questions/5689966/how-to-check-if-an-element-exists-in-the-xml-using-xpath]

 

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2019.12.17

옛날 글이라 그런가 링크가 깨졌네

The boolean function converts its argument to a boolean as follows:

  • a number is true if and only if it is neither positive or negative zero nor NaN

  • a node-set is true if and only if it is non-empty

  • a string is true if and only if its length is non-zero

  • an object of a type other than the four basic types is converted to a boolean in a way that is dependent on that type

[링크 : https://stackoverflow.com/questions/5689966/how-to-check-if-an-element-exists-in-the-xml-using-xpath]

[링크 : http://www.w3.org/TR/xpath/#function-boolean] << 옛날 링크

 

Rules

The function computes the effective boolean value of a sequence, defined according to the following rules. See also Section 2.4.3 Effective Boolean Value XP31.

  • If $arg is the empty sequence, fn:boolean returns false.

  • If $arg is a sequence whose first item is a node, fn:boolean returns true.

  • If $arg is a singleton value of type xs:boolean or a derived from xs:boolean, fn:boolean returns $arg.

  • If $arg is a singleton value of type xs:string or a type derived from xs:string, xs:anyURI or a type derived from xs:anyURI, or xs:untypedAtomic, fn:boolean returns false if the operand value has zero length; otherwise it returns true.

  • If $arg is a singleton value of any numeric type or a type derived from a numeric type, fn:boolean returns false if the operand value is NaN or is numerically equal to zero; otherwise it returns true.

[링크 : https://www.w3.org/TR/xpath-functions-31/#func-boolean] << 새로운 링크?

 

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Posted by 구차니

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unnest를 사용하니 ,로 구분된 리스트를 여러개의 열로 나눌수 있었다.

string_to_array()의 반대 개념이라고 하면 되려나?

 

regexp_split_to_table() 도 사용할 수 있으나 regexp의 cost가 비싼 편이라 추천은 안하는 듯

[링크 : https://stackoverflow.com/questions/29419993/split-column-into-multiple-rows-in-postgres]

  [링크 : https://www.postgresql.org/docs/current/functions-string.html#FUNCTIONS-STRING-OTHER]

 

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예제에 따라 다르지만 select에서 써도 되고 from에서 lateral join으로 구현해도 되고

어느게 cost가 낮을려나?

[링크 : https://www.postgresql.org/docs/9.2/functions-array.html]

[링크 : https://wwwi.tistory.com/350]

 

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Posted by 구차니

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The operator ~~ is equivalent to LIKE, and ~~* corresponds to ILIKE. There are also !~~ and !~~* operators that represent NOT LIKE and NOT ILIKE, respectively. All of these operators are PostgreSQL-specific.

[링크 : https://www.postgresql.org/docs/9.3/functions-matching.html]

 

SQL> select * from test where x ~ '[0-9]+';  -- "~" 는 "similar to" 의미입니다.

[링크 : https://www.postgresdba.com/bbs/board.php?bo_table=B10&wr_id=44]

Posted by 구차니

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