How does Oracle determine whether a field is numeric?

1 year ago
Olivia Parker
2 minutes

In Oracle, you can use the numerical function TO_NUMBER() to determine if a field is a number. The specific steps are as follows:

  1. By using the TO_NUMBER() function to convert the field to a number type, if the conversion is successful, it means the field is a number; if the conversion fails, it means the field is not a number.
  2. For example, consider a table named table_name, where a field column_name needs to be checked if it is a number.
  3. Retrieve the column_name from table_name where the value can be converted to a number.
  4. The SQL statement above will retrieve the records in the table “table_name” where the values in the column “column_name” are numbers.
  5. You can use the REGEXP_LIKE() function in combination with a regular expression to determine if a field consists of only digits (excluding decimal points, positive or negative signs, and other characters). For example, to check if the field column_name is a pure number.
  6. Choose the column from the table where it consists only of numbers.
  7. The above SQL statement will retrieve records from the table table_name where the column column_name contains only numbers.

Please note that when using the TO_NUMBER() function, an exception will be thrown if the field’s value cannot be converted to a valid number. Therefore, if you do not want the query to be interrupted by an exception but instead need to receive a result indicating whether the field is a number, you can use the TO_NUMBER() function in combination with the EXCEPTION keyword and NULL replacement. For example:

SELECT column_name,
       CASE WHEN TO_NUMBER(column_name) IS NULL THEN '非数字' ELSE '数字' END AS is_numeric
FROM table_name;

The SQL statement mentioned above will return the column_name field from the table table_name, along with a new field called is_numeric which will indicate whether the column_name field is a number. If the column_name field is a number, the value of the is_numeric field will be ‘numeric’; if the column_name field is not a number, the value of the is_numeric field will be ‘non-numeric’.

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