private String buildConnectionByAllReplace(boolean allReplace, String col) {
        String conncetionSql = allReplace ? quoteIdentifier("T1") + "." + quoteIdentifier(col) + " = " + quoteIdentifier("T2") + "." + quoteIdentifier(col) :
                quoteIdentifier("T1") + "." + quoteIdentifier(col) + " =nvl(" + quoteIdentifier("T2") + "." + quoteIdentifier(col) + ","
                        + quoteIdentifier("T1") + "." + quoteIdentifier(col) + ")";
        return conncetionSql;
    }
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