What's the Difference Between `YYYY` and `RRRR` Year Formats in Oracle SQL's `TRUNC` Function?

Unveiling the Distinction between 'YYYY' and 'RRRR' in Oracle SQL

In Oracle SQL, the formats 'YYYY' and 'RRRR' both appear to produce the same result when used with the trunc() function in the context of year-based truncations. However, a subtle difference exists between the two.

'YYYY': A Static Representation of the Year

The 'YYYY' format represents the year in a four-digit form, regardless of the input. This means that '27-Jul-1987' will always be truncated to '1987' using this format.

'RRRR': Contextual Year Interpretation

The 'RRRR' format, on the other hand, introduces a specific interpretation rule for years given as two digits. Specifically:

• Years in the range 00 to 49 are assumed to belong to the current century, using the same first two digits as the current year.
• Years in the range 50 through 99 are assumed to belong to the previous century.

This rule ensures that dates like '27-Jul-1987' are interpreted consistently, regardless of the current century.

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