uk.ac.starlink.table.jdbc

Class SqlSyntax

java.lang.Object

uk.ac.starlink.table.jdbc.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

Field Summary

Fields

Modifier and Type	Field and 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 and Description
SqlSyntax(java.lang.String[] reservedWords, java.util.regex.Pattern identifierRegex, char quoteChar) Constructor.

Method Summary

Modifier and Type	Method and 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