oracle character conversion number

Oracle character conversion number

In the Oracle database, we often need to convert character type data into numeric type data. For example, we need to convert the order quantity field stored in the database from character type to numeric type to facilitate statistical calculations. This article will introduce several methods of converting characters into numbers in Oracle.

Method 1: Use TO_NUMBER()

TO_NUMBER() is one of Oracle's built-in functions, used to convert character type data into numeric type data. The following is the syntax for using the TO_NUMBER() function:

TO_NUMBER(char, format)

Among them, the char parameter is the character type data to be converted, and the format parameter is optional. Use The format of the number in the specified char parameter. The TO_NUMBER() function returns a numeric value. If the char parameter cannot be converted to a number, the function will return an error.

The following is an example to convert the string "12345" into numeric type data:

SELECT TO_NUMBER('12345') from dual;

After executing this statement , will return a numeric value 12345.

When using the TO_NUMBER() function to convert characters to numbers, you need to pay attention to the following points:

1. If the converted character type data contains non-numeric characters, the conversion function will throw An error message appears.
2. When using the format parameter for conversion, you need to ensure that the format of the number in the char parameter is consistent with the number format specified in the format parameter. Otherwise, the conversion function will return an error.
3. TO_NUMBER() function supports many number formats, including currency format, percentage format, etc. The appropriate number format needs to be selected based on the actual situation.

Method 2: Use CAST()

In addition to the TO_NUMBER() function, we can also use the CAST() function to convert characters to numbers. The CAST() function is a common function in Oracle and can be used to convert one data type to another data type. The following is the syntax for using the CAST() function:

CAST(char AS datatype)

Among them, the char parameter is the character type data to be converted, and the datatype parameter is the data type to be converted. , including numerical values, dates, characters, etc.

The following is an example to convert the string "12345" into numeric type data:

SELECT CAST('12345' AS NUMBER) FROM dual;

Execute this After the statement, a numeric value 12345 will be returned.

When using the CAST() function to convert characters to numbers, you need to pay attention to the following points:

1. Same as the TO_NUMBER() function, if the converted character type data contains non-digits characters, the conversion function will throw an error message.
2. It is necessary to ensure that the number in the char parameter conforms to the format required by the datatype parameter. Otherwise, the conversion function will return an error.
3. The CAST() function uses standard SQL data types and can be found to be more flexible than TO_NUMBER() in converting data types.

Method 3: Use REGEXP_REPLACE()

We can also use the REGEXP_REPLACE() function to convert characters to numbers. The REGEXP_REPLACE() function is a function that uses regular expressions in Oracle, and its usage is similar to other regular expressions. The following is the syntax for using the REGEXP_REPLACE() function:

REGEXP_REPLACE(char, pattern, replace)

Among them, the char parameter is the character type data to be converted, and the pattern parameter is to be replaced. Character rules, the replace parameter is the character or number to be replaced.

The following is an example to convert the string "12345" into numeric type data:

SELECT REGEXP_REPLACE('12345', '¹', '') FROM dual;

After executing this statement, a numeric value 12345 will be returned.

When using the REGEXP_REPLACE() function to convert characters into numbers, you need to pay attention to the following points:

1. Similar to other regular expressions, you need to ensure that the character rules (pattern parameters) used are correct .
2. When using the REGEXP_REPLACE() function to convert characters into numbers, the efficiency may not be as high as other functions.

Summary

Through the above introduction, we can see that there are three ways to convert characters to numbers in Oracle: using the TO_NUMBER() function, using the CAST() function and using REGEXP_REPLACE() function. Different methods need to be selected for conversion depending on the specific situation. When using these functions, you need to pay attention to ensuring that the character rules are correct, the number format is correct, and the performance is efficient to ensure correct conversion results.

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