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From "Parthasarathy T" <parth...@gmail.com>
Subject Doubt in the SQLExpression formed by buildLike method
Date Thu, 12 Oct 2006 09:11:40 GMT
Hi all,

I have a small doubt in the SQLExpression formed by the buildLike method. If
i understand the comments correctly if criteria = 50\%, it will be changed
to columnName = 50%

/**
     * Takes a columnName and criteria and builds an SQL phrase based
     * on whether wildcards are present and the state of the
     * ignoreCase flag.  Multicharacter wildcards % and * may be used
     * as well as single character wildcards, _ and ?.  These
     * characters can be escaped with \.
     *
     * e.g. criteria = "fre%" -> columnName LIKE 'fre%'
     *                        -> UPPER(columnName) LIKE UPPER('fre%')
     *      criteria = "50\%" -> columnName = '50%'
     *
     * @param columnName A column name.
     * @param criteria The value to compare the column against.
     * @param comparison Whether to do a LIKE or a NOT LIKE
     * @param ignoreCase If true and columns represent Strings, the
     * appropriate function defined for the database will be used to
     * ignore differences in case.
     * @param db Represents the database in use, for vendor specific
functions.
     * @param whereClause A StringBuffer to which the sql expression
     * will be appended.
     */
    static void buildLike(String columnName,
                           String criteria,
                           SqlEnum comparison,
                           boolean ignoreCase,
                           DB db,
                           StringBuffer whereClause)
    {

Check the loop logic below - first sb is filled with *5 *and then *0 *and
then it encounters \ - the code now enters the *case BACKSLASH: *where we
check the next character while is % so it enters the % case and so the
position gets incremented by 1 automatically - the checkWildcard at this
time will be still \ and not % and so when the checkWildcard gets appended
to sb we will be appending \ and we would have skipped % altogether (because
of position++)
At the end of the loop we will be having sb= 50\ and not 50%. Is this a
bug??

Most of time we may not have faced the problem because we would have come in
criteria = 50\\% (because of *quoteAndEscapeText() *method appending an
extra slash for most dbs).

StringBuffer sb = *new* StringBuffer();

*  StringBuffer sb = new StringBuffer();
        while (position < criteria.length())
        {
            char checkWildcard = criteria.charAt(position);*

*            switch (checkWildcard)
            {
            case BACKSLASH:
                // Determine whether to skip over next character.
                switch (criteria.charAt(position + 1))
                {
                case '%':
                case '_':
                case '*':
                case '?':
                case BACKSLASH:
                    position++;
                    break;
                }
                break;
            case '%':
            case '_':
                escapeCharFound = true;
                equalsOrLike = comparison.toString();
                break;
            case '*':
                equalsOrLike = comparison.toString();
                checkWildcard = '%';
                break;
            case '?':
                equalsOrLike = comparison.toString();
                checkWildcard = '_';
                break;
            }*

*            sb.append(checkWildcard);
            position++;
        }
        whereClause.append(equalsOrLike);*

sb.append(checkWildcard);

position++;

}

Thanks,

*T.Parthasarathy *•  SunGard  • Offshore Services • Divyasree Chambers
Langford Road • Bangalore 560025 India
Tel +91-80-2222-0501 • Mobile +91-99450-00394 • Fax +91-80-2222-0511 • *
www.sungard.com*

*Please note my email address –
Parthasarathy.Thandavarayan@sos.sungard.com.  Please update your
contact list and use this address for all
future communication.*

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