Java.sql.SQLSyntaxErrorException: ORA-01795: maximum number of expressions in a list is 1000

Introduction

When working with databases in Java, it is common to encounter errors related to SQL syntax. One such error is java.sql.SQLSyntaxErrorException: ORA-01795: maximum number of expressions in a list is 1000. This error occurs when you are trying to execute a SQL query that has more than 1000 expressions in a list. In this article, we will explore the causes of this error and discuss possible solutions.

Understanding the Error

To understand the error, let's break down the message ORA-01795: maximum number of expressions in a list is 1000.

  • ORA-01795: This is the Oracle error code that indicates the maximum number of expressions error.
  • maximum number of expressions in a list is 1000: This part of the error message informs us that the maximum number of expressions allowed in a list is 1000.

Causes of the Error

The ORA-01795 error can occur in various scenarios, such as:

  1. Using the IN operator with a list that contains more than 1000 elements.
  2. Inserting or updating multiple rows using the VALUES clause, where the number of rows exceeds 1000.

Example Scenario

Let's consider an example scenario where we encounter this error. Assume we have a table called employees with columns id and name. We want to retrieve records for employees with specific IDs. We have a list of employee IDs stored in a Java List object.

List<Integer> employeeIds = Arrays.asList(1, 2, 3, ..., 1001);

To retrieve the records, we construct a SQL query using the IN operator and concatenate the employee IDs from the list:

String sql = "SELECT * FROM employees WHERE id IN (" + employeeIds.stream().map(Object::toString).collect(Collectors.joining(",")) + ")";

When executing this query, we encounter the ORA-01795 error because the employeeIds list contains more than 1000 elements.

Solution - Batch Processing

To overcome the ORA-01795 error, we can use batch processing. Batch processing involves dividing the large list into smaller chunks and executing multiple queries to retrieve the desired result.

Here's an example of how we can modify our code to implement batch processing:

int batchSize = 500;
int totalRecords = employeeIds.size();
int batches = (int) Math.ceil((double) totalRecords / batchSize);

for (int i = 0; i < batches; i++) {
    int startIndex = i * batchSize;
    int endIndex = Math.min(startIndex + batchSize, totalRecords);

    List<Integer> batchIds = employeeIds.subList(startIndex, endIndex);

    String sql = "SELECT * FROM employees WHERE id IN (" + batchIds.stream().map(Object::toString).collect(Collectors.joining(",")) + ")";
    
    // Execute the SQL query and process the results
}

In this code, we divide the employeeIds list into batches of size batchSize (e.g., 500). We then construct a SQL query for each batch, retrieve the records, and process the results. By executing multiple smaller queries, we avoid the ORA-01795 error.

Conclusion

In this article, we discussed the java.sql.SQLSyntaxErrorException: ORA-01795: maximum number of expressions in a list is 1000 error that can occur when working with databases in Java. We explored the causes of this error and provided a solution using batch processing. By dividing the large list into smaller batches and executing multiple queries, we can overcome the limitation of 1000 expressions in a list. It is important to handle such errors properly to ensure the smooth functioning of database operations in Java.

Note: The code examples provided are simplified and may require additional error handling and database-specific modifications for your use case.