PLS-01451：The data types of these value expressions must be comparable

错误原因：The data types of these value expressions must be comparable. Section 4.2 of X3H2, "Data types", states that: "A character string and a number are not comparable values." Many builtin functions in STANDARD will be flagged with this warning by means of a pragma. This warning will be place on data-type coercion functions, for example, TO_CHAR(number), that are inserted in OracleSQL to allow non-conforming data type combinations.