ora-00920

3 min read 26-02-2025

The Oracle error ORA-00920, "invalid relational operator," is a common SQL error indicating a problem with the comparison operators used in your WHERE clause. This means there's something wrong with the way you're trying to compare values in your SQL query. This article will explain the error, its causes, and how to fix it.

Understanding ORA-00920

The ORA-00920 error arises when Oracle's SQL parser encounters an operator it doesn't recognize in a comparison, such as in a WHERE clause. This often stems from typos, incorrect syntax, or using unsupported operators in specific contexts. The error message itself doesn't always pinpoint the exact problem, requiring careful examination of your SQL statement.

Common Causes of ORA-00920

Several factors can lead to this error. Let's explore the most frequent ones:

1. Typos and Case Sensitivity

SQL is case-insensitive in most contexts (depending on your database settings), but typos can still cause problems. For example, writing wHERE instead of WHERE or misspelling operators like = (equals) or <> (not equals) can trigger ORA-00920. Double-check your spelling and capitalization.

2. Incorrect Operator Usage

Using incorrect operators for the data types you're comparing is a common mistake. Make sure you're using the appropriate operator for your data:

= (Equals): For exact matches.
!= or <> (Not Equals): For values that are not equal.
> (Greater Than): For values larger than a specified value.
< (Less Than): For values smaller than a specified value.
>= (Greater Than or Equals): For values larger than or equal to a specified value.
<= (Less Than or Equals): For values smaller than or equal to a specified value.
BETWEEN: To check if a value falls within a range.
LIKE: For pattern matching (using wildcards % and _).
IN: To check if a value exists within a list.

Incorrect usage of these operators, especially with strings or dates, frequently results in ORA-00920. Ensure that your data types and operators are compatible.

3. Missing or Incorrect Quotes

String literals in SQL must be enclosed in single quotes ('). Forgetting these quotes or using double quotes (") can lead to the ORA-00920 error. Pay close attention to string comparisons.

4. Issues with Dates and Timestamps

Comparing dates and timestamps requires careful attention to formatting. Ensure your date/timestamp literals are formatted correctly according to Oracle's standards, and use appropriate date functions if necessary (e.g., TO_DATE). Incorrect formatting can generate ORA-00920.

5. Incorrect Use of Special Characters

Special characters within strings might require escaping (e.g., using a backslash \ before a single quote within a string). Incorrect handling of special characters can confuse the parser and cause ORA-00920.

Troubleshooting and Solutions

Carefully Review Your SQL: Start by meticulously examining your SQL statement, paying close attention to the WHERE clause. Look for typos, incorrect operator usage, and missing or misplaced quotes.
Check Data Types: Verify that the data types in your comparison are compatible. Implicit type conversions can sometimes fail, causing ORA-00920. Explicitly cast data types if needed.
Simplify Your Query: Break down complex WHERE clauses into smaller, simpler ones to isolate the problematic part. This can help you pinpoint the exact source of the error.
Test with Simple Comparisons: Create simple test queries to check individual comparisons to rule out issues with specific operators or data.
Use Explicit Casting: If you're comparing different data types, explicitly cast them to a common type to avoid implicit conversions that might fail. For instance:
```
SELECT * FROM my_table WHERE TO_CHAR(my_date_column) = '2024-10-26'; 
```
Examine Error Context: The error message might provide a clue about the location of the error within your SQL statement. Look at the line numbers and surrounding code to help you identify the problematic section.

Example Scenarios and Solutions

Scenario 1: Typo in Operator

SELECT * FROM employees WHERE salary > salry; --Typo in 'salary'

Solution: Correct the typo:

SELECT * FROM employees WHERE salary > salary;

Scenario 2: Missing Quotes

SELECT * FROM products WHERE name = Product X; --Missing quotes around product name

Solution: Add quotes:

SELECT * FROM products WHERE name = 'Product X';

Scenario 3: Incompatible Data Types

SELECT * FROM orders WHERE order_date = 'October 26, 2024'; --Incorrect date format

Solution: Use the correct date format and TO_DATE function:

SELECT * FROM orders WHERE order_date = TO_DATE('26-OCT-2024', 'DD-MON-YYYY');

By carefully checking your SQL syntax, data types, and operator usage, you can effectively resolve ORA-00920 and get your queries working correctly. Remember to always double-check your code for any errors, and don't hesitate to use tools such as SQL Developer or similar IDEs that provide syntax highlighting and error detection features.