How to convert oracle into numbers

Oracle is one of the world's famous database systems with a wide range of applications, especially in enterprise-level applications. In Oracle, there are many data types, such as strings, dates, numbers, etc. However, sometimes we need to convert certain data types in Oracle into numeric types to facilitate our calculations, comparisons and other operations. This article will introduce how to convert different data types into numeric types in Oracle.

1. Convert a string to a number

In Oracle, the easiest way to convert a string to a number is to use the TO_NUMBER() function. The syntax of this function is TO_NUMBER(string, format), where string is the string that needs to be converted, and format is optional and is used to specify the output format. If format is not specified, Oracle will automatically recognize the numbers in the string and convert them into numbers. Here is an example:

SELECT TO_NUMBER('123') FROM DUAL;

The result returned by this query is the number 123.

In addition, if the string contains non-numeric characters, the TO_NUMBER() function will return an error. Therefore, when using the TO_NUMBER() function, make sure that the string contains only numeric characters.

If you need to remove non-numeric characters from a string, you can use the REGEXP_REPLACE() function. Here is an example:

SELECT TO_NUMBER(REGEXP_REPLACE('1,234.56', '¹.]', '')) FROM DUAL;

This query will remove commas and periods from the string and convert the result into a number. It should be noted that this function will only remove non-numeric characters from the string and will not perform rounding or other processing.

2. Convert date into number

In Oracle, the date type is a very common type. Sometimes we need to convert dates into numeric types to facilitate calculations. Oracle provides two methods to convert dates into numbers, using the TO_NUMBER() function and using the DATE_TO_JULIAN() function.

The method of using the TO_NUMBER() function to convert dates to numbers is similar to the method of converting strings to numbers. Here is an example:

SELECT TO_NUMBER(TO_CHAR(SYSDATE, 'yyyy')) FROM DUAL;

This query returns the number of the current year. It should be noted that when converting a date into a string, the output format needs to be specified.

The method of using the DATE_TO_JULIAN() function to convert a date into a number is to convert the date into a Julian day, and then convert the Julian day into a number. The following is an example:

SELECT DATE_TO_JULIAN(SYSDATE) FROM DUAL;

This query returns the Julian day of the current date, which is a numeric type.

3. Convert other types into numbers

In Oracle, there are some other types, such as BOOLEAN type, BINARY_INTEGER type, etc. Although these types are not numeric types, sometimes we need to convert them to numeric types. At this time, you can use the CAST() function or TO_NUMBER() function for conversion.

The syntax for using the CAST() function to convert other types into numbers is CAST(value AS NUMBER), where value is the value that needs to be converted. Here is an example:

SELECT CAST(TRUE AS NUMBER) FROM DUAL;

This query returns the number 1, which means true.

The method of using the TO_NUMBER() function to convert other types into numbers also applies to BOOLEAN types and BINARY_INTEGER types. Here is an example:

SELECT TO_NUMBER(TRUE) FROM DUAL;

This query also returns the number 1.

It should be noted that if a non-numeric type is converted to a numeric type, an error will occur. Therefore, when using these functions, be sure that the value to be converted is legal. At the same time, you also need to pay attention to the numerical type range of the output to prevent overflow and other problems.

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