Class SqlSyntax


  • public class SqlSyntax
    extends java.lang.Object
    Summarises some aspects of the syntax of an SQL variant, and provides some utilities based on that.
    Since:
    7 Jun 2013
    Author:
    Mark Taylor
    • Field Summary

      Fields 
      Modifier and Type Field Description
      static java.util.regex.Pattern SQL92_IDENTIFIER_REGEX
      Standard regular expression for identifiers, as per SQL92.
      static java.lang.String[] SQL92_RESERVED
      SQL92 list of reserved words.
    • Constructor Summary

      Constructors 
      Constructor Description
      SqlSyntax​(java.lang.String[] reservedWords, java.util.regex.Pattern identifierRegex, char quoteChar)
      Constructor.
    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      static java.lang.String[] getParanoidReservedWords()
      Returns a list of words that are known to be reserved in a mixed bag of popular RDBMSs.
      java.util.SortedSet<java.lang.String> getReservedWords()
      Returns an alphabetical list of the reserved words known by this class, in normalised (upper case) form.
      boolean isIdentifier​(java.lang.String word)
      Indicates whether a given word is syntactically permitted to act as an identifier.
      boolean isReserved​(java.lang.String word)
      Indicates whether a given word is reserved.
      java.lang.String quote​(java.lang.String word)
      Returns a quoted version of a word.
      java.lang.String quoteIfNecessary​(java.lang.String word)
      Returns a string which can be used within an SQL query to refer to an item with the name of a given word.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Field Detail

      • SQL92_IDENTIFIER_REGEX

        public static final java.util.regex.Pattern SQL92_IDENTIFIER_REGEX
        Standard regular expression for identifiers, as per SQL92.
      • SQL92_RESERVED

        public static final java.lang.String[] SQL92_RESERVED
        SQL92 list of reserved words. This list was actually taken from ADQL 2.0 standard.
    • Constructor Detail

      • SqlSyntax

        public SqlSyntax​(java.lang.String[] reservedWords,
                         java.util.regex.Pattern identifierRegex,
                         char quoteChar)
        Constructor.
        Parameters:
        reservedWords - list of words considered reserved for this dialect
        identifierRegex - regular expression for an identifier token in this dialect
        quoteChar - character which may be used to quote words in this dialect (thus avoiding their usual parsing); words are quoted with a copy of this character at start and end, doubled if this character is embedded
    • Method Detail

      • getReservedWords

        public java.util.SortedSet<java.lang.String> getReservedWords()
        Returns an alphabetical list of the reserved words known by this class, in normalised (upper case) form.
        Returns:
        unmodifiable set of reserved words
      • isReserved

        public boolean isReserved​(java.lang.String word)
        Indicates whether a given word is reserved. The result is not sensitive to the case of the supplied word.
        Parameters:
        word - word to test
        Returns:
        true iff reserved
      • isIdentifier

        public boolean isIdentifier​(java.lang.String word)
        Indicates whether a given word is syntactically permitted to act as an identifier.
        Parameters:
        word - word to test
        Returns:
        true iff identifier
      • quoteIfNecessary

        public java.lang.String quoteIfNecessary​(java.lang.String word)
        Returns a string which can be used within an SQL query to refer to an item with the name of a given word. If the given word can be used as it stands, it is returned as given. Otherwise (if it's reserved or syntactically unsuitable) a quoted version of the provided word is returned.
        Parameters:
        word - word to use
        Returns:
        quoted or unquoted version of word
      • quote

        public java.lang.String quote​(java.lang.String word)
        Returns a quoted version of a word.

        Note that quoting words is not harmless - unlike for instance shell syntax, quotes are not just stripped off where present before processing, but instead in SQL92 and hence ADQL they modify the interpretation of what's quoted. This is something to do with the way case folding is handled, and I (mbt) didn't know about it until Markus Demleitner persuaded me it's actually true. As it happens MySQL behaves contrary to the standard in this respect (quoting of column names - but not table names?? - is harmless) but (for instance) PostgreSQL does not. Therefore do not use this method indiscriminately, use quoteIfNecessary instead.

        Parameters:
        word - word to quote
        Returns:
        quoted word
      • getParanoidReservedWords

        public static java.lang.String[] getParanoidReservedWords()
        Returns a list of words that are known to be reserved in a mixed bag of popular RDBMSs.
        Returns:
        reserved word list