Oracle determines whether it is a number

Oracle is a relational database management system that provides many powerful data processing and storage functions. In databases, it is often necessary to determine whether certain data is of numeric type. This article will introduce several Oracle methods to determine whether it is a number.

1. Using regular expressions

Regular expressions can be used in Oracle to determine whether a string is a numeric type. This can be achieved using the REGEXP_LIKE function.

Grammar:

REGEXP_LIKE(string, pattern)

Among them, string represents the string to be judged, and pattern represents the pattern of the regular expression.

If you want to determine whether a string is all numbers, you can use the following pattern:

'^d+$'

Among them, ^ represents the beginning of the string, $ represents the end of the string, and d represents any one Number, means match one or more.

Example:

SELECT REGEXP_LIKE('123', '^d+$') FROM DUAL;
-- 结果为1，表示字符串为数字类型

SELECT REGEXP_LIKE('12a', '^d+$') FROM DUAL;
-- 结果为0，表示字符串不是数字类型

2. Using the TO_NUMBER function

The TO_NUMBER function can also be used in Oracle to convert a string into a number. The TO_NUMBER function throws an exception if the string cannot be converted to a number.

You can use exception handling statements to determine whether a string is a numeric type.

Syntax:

BEGIN
  -- 尝试将字符串转换为数字
  v_num := TO_NUMBER(v_str);
EXCEPTION
  -- 如果出现异常，说明字符串不是数字类型
  WHEN VALUE_ERROR THEN
    v_num := NULL;
END;

Among them, v_str represents the string to be converted, and v_num represents the converted number. If the conversion is successful, v_num will be assigned the corresponding number; if the conversion fails, the TO_NUMBER function will throw a VALUE_ERROR exception, and v_num will be assigned the value NULL.

Example:

DECLARE
  v_str VARCHAR2(10) := '123';
  v_num NUMBER;
BEGIN
  BEGIN
    v_num := TO_NUMBER(v_str);
    DBMS_OUTPUT.PUT_LINE('是数字类型');
  EXCEPTION
    WHEN VALUE_ERROR THEN
      v_num := NULL;
      DBMS_OUTPUT.PUT_LINE('不是数字类型');
  END;
END;

3. Use a combination of regular expressions and the TO_NUMBER function

If you need to determine whether a string is a numeric type at the same time, and It is converted to a number, which can be used in combination with regular expressions and the TO_NUMBER function.

You can first use the REGEXP_LIKE function to determine whether the string is a numeric type. If so, use the TO_NUMBER function to convert it into a number; otherwise, return NULL.

Grammar:

CASE WHEN REGEXP_LIKE(string, '^d+$')
     THEN TO_NUMBER(string)
     ELSE NULL
END

Among them, string represents the string to be judged.

Example:

SELECT CASE WHEN REGEXP_LIKE('123', '^d+$')
            THEN TO_NUMBER('123')
            ELSE NULL
       END
FROM DUAL;
-- 结果为123，表示字符串为数字类型

SELECT CASE WHEN REGEXP_LIKE('12a', '^d+$')
            THEN TO_NUMBER('12a')
            ELSE NULL
       END
FROM DUAL;
-- 结果为NULL，表示字符串不是数字类型

Summary:

Whether you use regular expressions, the TO_NUMBER function or their combination, you can determine whether a string is a numeric type in Oracle function. In actual use, the appropriate method can be selected according to specific needs.

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