mysql插入数据时检查是否某字段已存在

SELECT
" +
                                                                    "	'',
" +
                                                                    "	'{0}',
" +
                                                                    "	'{1}',
" +
                                                                    "	'{2}'
" +
                                                                    "FROM
" +
                                                                    "	DUAL
" +
                                                                    "WHERE
" +
                                                                    "	NOT EXISTS (
" +
                                                                    "		SELECT
" +
                                                                    "			字段0
" +
                                                                    "		FROM
" +
                                                                    "			表
" +
                                                                    "		WHERE
" +
                                                                    "			字段0= '{0}'
" +
                                                                    "	)";

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