oracle convert to string

Oracle is one of the most widely used relational databases on the market. In daily database operations, we often need to present data in the Oracle database in the form of strings. This article will introduce how to convert data in Oracle database into strings.

1. Using the TO_CHAR() function

The TO_CHAR() function is a function in Oracle that converts any data type to a character type. The syntax of this function is:

TO_CHAR( expression [, format_mask [, nls_language ]] )

where expression is the input value to be converted, which can be a date, number or other data type; format_mask is an optional parameter, used to specify the conversion format; nls_language is an optional parameter, used to specify the language used when converting to a string. If format_mask is not specified, the function converts expression to a string according to the default format.

The following are some common usage examples:

• Convert date to string:

SELECT TO_CHAR(sysdate, 'yyyy-mm-dd hh24:mi:ss') FROM dual;

The above statement converts the current date into a string and displays it in the format of "year-month-day hour:minute:second".

• Convert numbers into strings:

SELECT TO_CHAR(123.45, '999.99') FROM dual;

The above statement converts the number 123.45 into String and displayed in the format of "

.##". If the entered number is negative, the string will be preceded by a minus sign.

2. Using the CAST() function

The CAST() function can be used to convert data types in Oracle to other data types. If you want to convert a data type to a string, you can convert it to a VARCHAR2 type and then use the TO_CHAR() function to convert it to a string. The syntax of the CAST() function is:

CAST( expression AS data_type [(length)] )

where expression is the input value to be converted; data_type is the data type to be converted; length is an optional parameter that specifies the length of the converted data type. When converting a data type to a VARCHAR2 type, the length parameter can be omitted.

The following is an example of using the CAST() function and the TO_CHAR() function:

SELECT TO_CHAR(CAST(123.45 AS VARCHAR2(10))), TO_CHAR(CAST(sysdate AS VARCHAR2( 20)), 'yyyy-mm-dd hh24:mi:ss') FROM dual;

The above statement converts the number 123.45 and the current date into VARCHAR2 type respectively, and uses the TO_CHAR() function to convert them into The string is displayed. When converting a date into a string, you need to specify the conversion format.

Summary

There are many ways to convert data into strings in Oracle database. The common method is to use the TO_CHAR() function or CAST() function. Use the TO_CHAR() function to convert any data type into a string and support custom conversion formats; use the CAST() function to convert the specified data type into a VARCHAR2 type, and then use the TO_CHAR() function to convert it into a string . In practical applications, different conversion methods need to be selected according to specific needs to achieve the best results. ###

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