How to convert Oracle date to characters
Oracle is a widely used relational database management system with powerful functions and flexibility. In Oracle, date fields are usually stored in date or timestamp types. However, in some cases, it is necessary to convert date type to character type for better data analysis and processing. This article will introduce how to perform date conversion in Oracle.
Date types in Oracle
In Oracle, date and timestamp fields can be stored and managed using the following data types:
- DATE: This is in Oracle The most commonly used date type. It contains date and time information, accurate to the second. The format of DATE type is: DD-MON-YYYY HH24:MI:SS.
- TIMESTAMP: The timestamp type contains date and time information, accurate to nanoseconds. The format of TIMESTAMP type is:
YYYY-MM-DD HH24:MI:SS.FF.
- TIMESTAMP WITH TIME ZONE: The timestamp type contains time zone information.
How to convert date to character
Oracle provides many functions that can convert date type to character type. Here are some commonly used functions.
- TO_CHAR: Format the date into the specified character format. Here are some common formats:
- DD-MON-YYYY: The date format is "day-month-year" (for example: 01-JAN-2000).
- MM/DD/YYYY: The date format is "month/day/year", such as "01/01/2000".
- YYYY-MM-DD: The date format is "year-month-day", such as "2000-01-01".
- HH24:MI:SS: The time format is "hour:minute:second", such as "15:30:45".
Example:
SELECT TO_CHAR(SYSDATE,'DD-MON-YYYY HH24:MI:SS') FROM dual;
This will return the current date and time in the format of "day-month-year hour:minute:second", for example "01-JAN-2000 15: 30:45".
- TO_DATE: Convert character type to date type. The syntax of the TO_DATE function is:
TO_DATE(char, format)
where "char" is the string to be converted, and "format" is the date format.
For example, convert "01-JAN-2000" to a date type:
SELECT TO_DATE('01-JAN-2000','DD-MON-YYYY') FROM dual;
This will return a date type of "2000-01-01".
- EXTRACT: Extract the year, month, day, hour, minute or second from the date. For example, to extract the month in the current date:
SELECT EXTRACT(MONTH FROM SYSDATE) FROM dual;
This will return the current month.
- ADD_MONTHS: Add or subtract months from the date. For example, to add 6 months to the current date:
SELECT ADD_MONTHS(SYSDATE, 6) FROM dual;
This will return the date 6 months after the current date.
- MONTHS_BETWEEN: Calculates the number of months between two dates. For example, to calculate the number of months between the current date and "01-JAN-2001":
SELECT MONTHS_BETWEEN(SYSDATE, TO_DATE('01-JAN-2001','DD-MON-YYYY')) FROM dual;
This will return a negative number indicating the number of months between the current date and "01-JAN-2001" number of months.
Summary
In Oracle, you can use functions such as TO_CHAR, TO_DATE, EXTRACT, ADD_MONTHS and MONTHS_BETWEEN to convert date types. These functions can help us effectively process date data to meet different data analysis and processing needs.
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