Introducing date format conversion in Oracle database

Oracle is a global information technology company that provides a variety of business software and hardware solutions. Among them, Oracle database is one of the most commonly used relational databases. The date type is one of the commonly used data types in Oracle database, but the format of the date has caused trouble for many people. In this article, we will cover date format conversion in Oracle database.

In Oracle, there are two date types: DATE and TIMESTAMP. Among them, the DATE type is accurate to seconds, and the TIMESTAMP type is accurate to microseconds. Although the storage formats of the two types are different, their handling of date format conversion is the same.

In Oracle, we can use the TO_CHAR function to convert date type to character type. The syntax of the TO_CHAR function is as follows:

TO_CHAR(date type, [format])

Among them, the date type refers to the date type data that needs to be converted, and the format refers to the final converted date. Format. Date formats in Oracle include English and numeric forms. Below we will introduce some common date formats.

1. Date format code:

Date format description

YYYY four-digit year
YY two-digit year
MM month, if not enough If there are two digits, add zeros in front
MON Three-letter month name
MONTH Full name of the month
DD Date, if there are less than two digits, add zeros in front
DAY Full name of the day
HH24 hours (24-hour format), if it is less than two digits, add zeros in front
HH hours (12-hour format), if it is less than two digits, add zeros in front
MI minutes , if it is less than two digits, add zeros in front
SS seconds, if it is less than two digits, add zeros in front

2. Example:

(1) Convert date For YYYY-MM-DD HH24:MI:SS format

SELECT TO_CHAR(SYSDATE, 'YYYY-MM-DD HH24:MI:SS') FROM DUAL;

The result is: 2022- 02-16 10:05:04

(2) Convert the date to YYYY-MM-DD format

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

The result is: 2022-02-16

(3) Convert the date to MON DAY, YYYY HH:MI:SS AM format

SELECT TO_CHAR(SYSDATE, 'MON DD, YYYY HH:MI:SS AM') FROM DUAL;

The result is: FEB 16, 2022 10:05:04 AM

In addition to the TO_CHAR function, Oracle also provides two dates Functions calculated between: MONTHS_BETWEEN and ADD_MONTHS.

The syntax of the MONTHS_BETWEEN function is as follows:

MONTHS_BETWEEN (earlier date type, later date type)

This function can calculate the months difference between two dates number. If the later date is earlier than the earlier date, the calculation is negative.

The syntax of the ADD_MONTHS function is as follows:

ADD_MONTHS (date type, number of months)

This function can add the specified number of months to a date and return the added later date.

In short, when dealing with Oracle's date format conversion, we need to first determine the required date format and perform conversions based on different date formats. By mastering date format codes, we can design more flexible and precise date formats.

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