oracle date conversion

Oracle is a popular relational database management system, and its DATE data type is very useful in handling dates and times. In Oracle database, DATE can store date and time values, but it needs to be converted when used. This article will introduce common methods of conversion of Oracle DATE data type.

1. TO_CHAR function

The TO_CHAR function can convert date values ​​into character types for use when querying or displaying results. Its syntax is as follows:

TO_CHAR(date, format)

Among them, date is the date value to be converted, and format is the parameter that specifies the output format. For example,

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

This will display the month, day, and year of the current date separated by '-'.

2. TO_DATE function

TO_DATE function can convert character type date values ​​to DATE type. Its syntax is as follows:

TO_DATE(char, format)

where char is the date value of the character type to be converted, format is the date value in string format, and the string specifies the date format. For example,

SELECT TO_DATE('2021-04-12', 'YYYY-MM-DD') FROM dual;

This will convert '2021-04-12' to date format value.

3. CAST function

The CAST function can convert between any data types. For DATE type, you can use the CAST function to convert it to another date format. The syntax is as follows:

CAST(expression AS datatype)

where expression is the date value to be converted, and datatype is the data type to be converted to. For example,

SELECT CAST(SYSDATE AS TIMESTAMP) FROM dual;

This will convert the current date to TIMESTAMP format.

4. EXTRACT function

The EXTRACT function can extract specific date components from DATE type date values, such as year, month, day, hour, minute, etc. The syntax is as follows:

EXTRACT (date_part FROM date_value)

Among them, date_part is the date component to be extracted, such as 'YEAR' represents the year, 'MONTH' represents the month, and 'DAY' represents the date , and 'date_value' is the DATE value from which the date component is to be extracted. For example,

SELECT EXTRACT(YEAR FROM SYSDATE) FROM dual;

This will display the year of the current date.

Summary:

Date and time are very important in Oracle database, and processing the DATE data type is a key component of Oracle database applications. This article introduces several common methods of date conversion in Oracle, including TO_CHAR, TO_DATE, CAST, EXTRACT functions and related syntax, parameters and examples. Proficiency in these functions can greatly improve efficiency in database query and management.

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