oracle convert to string

To convert dates, numbers or other data types into strings in Oracle database, you can use the TO_CHAR function. The usage of this function is introduced in detail below.

1. Basic usage of TO_CHAR function

In Oracle database, the TO_CHAR function is mainly used to convert a data type to a character type. The basic syntax is as follows:

TO_CHAR(expression, fmt [, nlsparam])

Among them:

• expression: specifies the data type that needs to be converted to a character type .
• fmt: Specifies the format of the converted character type. Can be in a date or numeric format. For the specific meaning of the format string, please refer to Oracle's official documentation.
• nlsparam (optional): Specifies the language used for the format string.

For example, the following example converts sysdate (system date) to character type:

SELECT TO_CHAR(sysdate, 'MM/DD/YYYY') FROM DUAL;

Will return a value such as "05/18/2021".

2. Convert numeric type to string

In Oracle database, you can use the TO_CHAR function to convert numeric type data to character type.

The following example code converts numeric type data to character type:

SELECT TO_CHAR(12345.67, '99999.99') FROM DUAL;

will return the value "12345.67".

3. Conversion of date type to string

In Oracle database, the method of converting date type data into string type is relatively complicated. Date conversion requires specifying the correct format string.

The following example converts sysdate to string type:

SELECT TO_CHAR(sysdate, 'MM-DD-YYYY') FROM DUAL;

will return "05-18 -2021".

4. Other character processing functions

In addition to the TO_CHAR function, Oracle database also has some commonly used string processing functions, such as:

• SUBSTR: used to intercept strings.
• INSTR: Used to return the position of the specified character in the string.
• CONCAT: used to connect two strings.
• REPLACE: Used to replace specified characters in a string.

For example, the following code shows how to use the SUBSTR function to intercept the contents of the string "Hello world":

SELECT SUBSTR('Hello world', 1, 5) FROM DUAL;

will return "Hello".

5. Conclusion

This article details the method of converting dates, numbers and other data types into strings in Oracle database. Understanding these methods can help developers better handle string data. In addition to these functions, there are many other commonly used character processing functions such as SUBSTR or INSTR. Mastering these functions allows us to better operate and process strings and improve our development efficiency.

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