private String buildConnectionConditions(String[] uniqueKeyFields) {
        return Arrays.stream(uniqueKeyFields).map(col -> "T1." + quoteIdentifier(col) + "=T2." + quoteIdentifier(col)).collect(Collectors.joining(" AND "));
    }
build   T1."A"=T2."A" or  T1."A"=nvl(T2."A",T1."A")
@param fieldNames
@param uniqueKeyFields
@param allReplace
@return
oracle/oracle-sink/src/main/java/com/dtstack/flink/sql/sink/oracle/OracleDialect.java