oracle character conversion date

Oracle character conversion date

In Oracle database, date data is stored in a specific format, and when we need to convert string type date data into date data, we can use Oracle Character conversion in date functions.

In Oracle, we can use three functions to complete the operation of character conversion to date. They are:

1. TO_DATE: This function can convert character data to date type. data.
2. TO_CHAR: This function can convert date data into character data.
3. TO_TIMESTAMP: This function can convert character data into timestamp data.

Below we will introduce these three functions respectively.

TO_DATE function

TO_DATE function is the most commonly used character conversion date function in Oracle. Its syntax is as follows:

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

Among them,

char: represents the string that needs to be converted;
format: represents the date format that needs to be converted, the default is 'DD-MON-YY';
nls_language: Indicates the language to be used, such as 'AMERICAN', 'FRENCH', etc. If not specified, the language used by the current user will be used by default.

The following is an example of using the TO_DATE function to convert character data to date data:

SELECT TO_DATE('2022-02-22 10:35:00', 'YYYY-MM -DD ​​HH24:MI:SS') FROM DUAL;

The execution result is: 2022/02/22 10:35:00.

Analysis:

In this example, we use the TO_DATE function to convert the string '2022-02-22 10:35:00' into date data. Among them, 'YYYY-MM-DD HH24:MI:SS' represents the date format of the string, that is, year-month-day hour: minute: second.

TO_CHAR function

TO_CHAR function is a function that converts date data into character data. Its syntax is as follows:

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

Among them,

date: indicates the date data that needs to be converted;
format: indicates the date format that needs to be converted, the default is 'DD-MON-YY';
nls_language: Indicates the language to be used, such as 'AMERICAN', 'FRENCH', etc. If not specified, the language used by the current user will be used by default.

The following is an example of using the TO_CHAR function to convert date data into character data:

SELECT TO_CHAR(SYSDATE, 'YYYY year MM month DD day HH hour MI minute SS second') FROM DUAL;

The execution result is: 14:23:29 on August 22, 2022.

Analysis:

In this example, we use the TO_CHAR function to convert the system's current time SYSDATE into character data. Among them, 'YYYY year MM month DD day HH hour MI minute SS second' represents the date format to be converted to, that is, year-, month, day, hour, minute, second.

TO_TIMESTAMP function

TO_TIMESTAMP function is a function that converts character data into timestamp data. Its syntax is as follows:

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

Among them,

char: represents the string that needs to be converted;
format: represents the date format that needs to be converted, the default is 'DD-MON-YY';
nls_language: Indicates the language to be used, such as 'AMERICAN', 'FRENCH', etc. If not specified, the language used by the current user will be used by default.

The following is an example of using the TO_TIMESTAMP function to convert character data into timestamp data:

SELECT TO_TIMESTAMP('2022-08-22 14:35:00', 'YYYY- MM-DD HH24:MI:SS') FROM DUAL;

The execution result is: 22-AUG-22 02.35.00.000000000 PM.

Analysis:

In this example, we use the TO_TIMESTAMP function to convert character data '2022-08-22 14:35:00' into timestamp data. Among them, 'YYYY-MM-DD HH24:MI:SS' represents the date format of the string, that is, year-month-day hour: minute: second.

Summary

The above is the operation of converting characters to dates in Oracle. We can use the three functions TO_DATE, TO_CHAR, and TO_TIMESTAMP to perform corresponding conversions. It should be noted that when using these functions, parameters such as date format and language need to be specified correctly to ensure the correctness of the conversion results.

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