How can dates and strings be converted back and forth in SQL?

In SQL, the following functions can be used to convert dates and strings back and forth:

1. Convert the date to a string.
2. TO_CHAR(date_value, format) : Convert a date value into a string with a specified format. For example, TO_CHAR(SYSDATE, ‘yyyy-mm-dd’) will return the current date in string form.
3. Convert the date value to a string of a specified length using CAST(date_value AS VARCHAR2(n)). For example, CAST(SYSDATE AS VARCHAR2(10)) will return the current date as a string.
4. Convert a string to a date:
5. TO_DATE(string_value, format): Converts a string value into a date according to the specified format. For example, TO_DATE(‘2022-01-01’, ‘yyyy-mm-dd’) will return a value of date type.
6. Convert a string value directly to a date type using CAST. For example, CAST(‘2022-01-01’ AS DATE) will return a value in date type.

It is important to note that when converting dates to strings, different date formats can be specified to obtain different forms of strings. When converting strings to dates, it is necessary to ensure that the format of the string is consistent with the specified date format, otherwise the conversion may fail.