Скачать или смотреть Resolving the ORA-01821: date format not recognized SQL Error

Discover effective solutions to the `ORA-01821` error in SQL when working with date formats. Learn how to correct your SQL statements for successful execution.
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Understanding the ORA-01821: date format not recognized Error

When working with SQL, especially when dealing with dates, encountering errors can be quite frustrating. One common issue is the ORA-01821: date format not recognized. This error occurs when SQL cannot interpret the date format you are using.

The Problem at Hand

In this case, you are attempting to determine the amount of films returned to a film store on a specific date ("2005.06.05") along with the number of films borrowed on that date. However, your SQL query produces the ORA-01821 error. This indicates that there is a problem with how the date is formatted in your SQL statements.

Breaking Down the SQL Query

The error likely stems from the fact that the date format you are using does not conform to the expected formats for SQL functions. In your original query, you have:

[[See Video to Reveal this Text or Code Snippet]]

This approach is problematic because '2005.06.05' is not a valid date format specifier; instead, it's just a fixed string.

Common Issues Leading to the Error:

Wrong Format Strings: Using specific date values as format strings instead of format specifiers.

Inconsistent Date Types: Not properly matching the types when comparing date values.

Solutions to Fix the SQL Query

1. Correcting TO_CHAR Function

Instead of using a concrete date format like '2005.06.05', you should use:

[[See Video to Reveal this Text or Code Snippet]]

This modification tells SQL that you want to convert the return_date into a string that matches the 'yyyy.mm.dd' format.

2. Fixing TO_TIMESTAMP Usage

Similarly, for the TO_TIMESTAMP function, where you are trying to compare dates, replace:

[[See Video to Reveal this Text or Code Snippet]]

with:

[[See Video to Reveal this Text or Code Snippet]]

This ensures that the input string matches the expected date structure.

The Revised SQL Query

Here's how your SQL statement would look after making these recommended changes:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By ensuring that you use appropriate format specifiers for date and timestamp functions, you can avoid the ORA-01821: date format not recognized error. SQL queries can be complex, but understanding how to format your dates correctly is essential for smooth execution.

If you continue to face challenges, consider debugging further by checking all date-related comparisons and format specifications in your queries. Happy querying!