This error occurs when PostgreSQL encounters an empty string in a context that requires a non-empty value, such as type casting or operations on specific columns. Fix it by validating input, using NULLIF to convert empty strings to NULL, or adjusting your schema constraints.
PostgreSQL distinguishes between empty strings ('') and NULL values, which is different from Oracle behavior. When an operation expects a non-empty string but receives an empty one, PostgreSQL throws a "Zero length character string" error (SQLSTATE 2200F). This commonly happens when attempting to cast empty strings to non-text types (integers, dates), inserting empty values into constrained columns, or performing operations that require non-empty input.
Enable PostgreSQL query logging to capture the exact statement causing the error:
ALTER SYSTEM SET log_statement = 'all';
SELECT pg_reload_conf();Then check the PostgreSQL logs to find the offending SQL query.
Add validation to prevent empty strings from reaching problematic operations. Use a CASE statement to handle empty strings:
SELECT CASE WHEN my_string ~ '[0-9]+' THEN my_string::integer ELSE 0 END FROM my_table;Or check string length before casting:
SELECT CASE WHEN length(my_string) > 0 THEN my_string::integer ELSE NULL END FROM my_table;Replace empty strings with NULL during inserts or updates, especially when migrating from Oracle:
INSERT INTO my_table (name, email) VALUES (NULLIF('', NULL), NULLIF('', NULL));
UPDATE my_table SET name = NULLIF(name, '') WHERE name = '';Or use a function to sanitize input:
SELECT COALESCE(NULLIF(user_input, ''), default_value) FROM my_table;Inspect the table definition for constraints that disallow empty strings:
\d table_nameLook for CHECK constraints or NOT NULL definitions. If needed, adjust constraints to allow NULL or empty strings, or provide a DEFAULT value:
ALTER TABLE table_name ALTER COLUMN column_name SET DEFAULT '';
ALTER TABLE table_name ADD CONSTRAINT check_not_empty CHECK (column_name != '');Before executing any query, validate input in your application code to prevent empty strings where they're not allowed:
// Node.js/JavaScript example
const isValidInput = (value) => value && value.trim().length > 0;
if (!isValidInput(userInput)) {
throw new Error('Input cannot be empty');
}For type casting, explicitly handle empty values:
const toInteger = (str) => str && str.trim() !== '' ? parseInt(str) : null;
const result = toInteger(userInput);PostgreSQL's strict separation between empty strings and NULL differs from Oracle, which treats them as equivalent in many contexts. When migrating from Oracle, systematically review code for empty string handling. Use NULLIF with character data types during migration: SELECT NULLIF(column_name, '') FROM table. For stored procedures, add input validation using string length checks (length(param) > 0) before type casting. In application frameworks like Prisma, validate data before sending to the database to catch empty strings early. Consider using text type with CHECK constraints instead of varchar(n) if you need to support empty strings explicitly.
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