private String buildConnectionConditions(String[] uniqueKeyFields) {
        return
            Arrays
                .stream(uniqueKeyFields)
                .map(col -> "T1." + quoteIdentifier(col) + "=T2." + quoteIdentifier(col))
                .collect(Collectors.joining(","));
    }
build    T1."A"=T2."A" or  T1."A"=nvl(T2."A",T1."A")

@param fieldNames
@param uniqueKeyFields
@param allReplace
@return
sqlserver/sqlserver-sink/src/main/java/com/dtstack/flink/sql/sink/sqlserver/SqlserverDialect.java