oracle date conversion

Oracle Date Conversion

In Oracle database, date is a very important data type, because many applications need to calculate and process dates. However, the date format may be different in different countries and regions, which requires date format conversion in the Oracle database.

Oracle database has rich built-in functions for processing dates and times, which allows us to easily calculate and convert dates. In this article, I will introduce some commonly used Oracle Date conversion functions and how to use them.

1. TO_DATE function

TO_DATE function is used to convert character date to date data. The syntax is as follows:

TO_DATE(char,[format],[nls_language])

Among them, char is the character date to be converted, format is the conversion format, and nls_language is the language parameter. If the format and language parameters are not specified, the default values ​​are used.

For example, to convert the string '20220326' into date data, you can use the following statement:

SELECT TO_DATE('20220326','yyyymmdd') FROM DUAL;

2. TO_CHAR function

TO_CHAR function is used to convert date data into character data. The syntax is as follows:

TO_CHAR(date,[format],[nls_language])

Among them, date is the date data to be converted, format is the conversion format, and nls_language is the language parameter. If the format and language parameters are not specified, the default values ​​are used.

For example, to convert date data '2022-03-26' to character data, you can use the following statement:

SELECT TO_CHAR(to_date('2022-03-26', 'yyyy-mm-dd'),'yyyy year mm month dd day') FROM DUAL;

3. TRUNC function

The TRUNC function is used to convert date data into Specify format truncation. The syntax is as follows:

TRUNC(date,[format])

Among them, date is the date data to be processed, and format is the truncated format. If no format is specified, the default is to truncate to the day.

For example, to truncate the date data '2022-03-26 13:20:30.123' to the day, you can use the following statement:

SELECT TRUNC(to_date('2022-03- 26 13:20:30.123','yyyy-mm-dd hh24:mi:ss.ff3'),'dd') FROM DUAL;

4. ADD_MONTHS function

## The #ADD_MONTHS function is used to add the specified number of months to date data. The syntax is as follows:

ADD_MONTHS(date, months)

Among them, date is the date data to be processed, and months is the number of months to be added.

For example, to add 3 months to the date '2022-03-26', you can use the following statement:

SELECT ADD_MONTHS(to_date('2022-03-26','yyyy -mm-dd'),3) FROM DUAL;

MONTHS_BETWEEN function

MONTHS_BETWEEN function is used to calculate the number of months between two date data. The syntax is as follows:

MONTHS_BETWEEN(date1, date2)

Among them, date1 and date2 are date data to be calculated and can be in any order.

For example, to calculate the number of months between the dates '2022-03-26' and '2021-11-28', you can use the following statement:

SELECT MONTHS_BETWEEN(to_date(' 2022-03-26','yyyy-mm-dd'),to_date('2021-11-28','yyyy-mm-dd')) FROM DUAL;

The above is the commonly used Oracle Date Introduction to conversion functions and how to use them. In actual use, these functions can be flexibly used as needed to process and convert dates.

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