ORA-06502: Character-to-Number Conversion Error Explained & Fixed

What is ORA-06502: PL/SQL numeric or value error?

ORA-06502 signals that Oracle attempted a data conversion that failed. The runtime engine raises it when converting a character value to a number, assigning data that exceeds variable length, or encountering numeric overflow inside PL/SQL.Developers see the error during anonymous blocks, stored procedures, triggers, or functions. It aborts execution, rolls back uncommitted work, and hides downstream errors until fixed.

What Causes This Error?

Character data containing non-numeric symbols triggers implicit conversion when assigned to NUMBER variables. Oracle stops at the first invalid byte and raises ORA-06502.Mismatched precision or scale, such as inserting 123.456 into NUMBER(5,2), causes numeric overflow and the same error code.VARCHAR2 or CHAR variables overflow when the source string is longer than the declared length, producing ORA-06502 with a value error subtype.

How to Fix ORA-06502

Validate and clean incoming text before conversion. Use explicit TO_NUMBER with a matching format mask to avoid implicit casting surprises.Resize variables and columns to accommodate real-world data. Increase VARCHAR2 length or widen NUMBER precision and scale.Add EXCEPTION handlers that log offending values and continue. Use DBMS_UTILITY.FORMAT_ERROR_BACKTRACE to pinpoint the exact line.

Common Scenarios and Solutions

Reading user input like '1,200' fails because of the comma. Replace commas then cast: TO_NUMBER(REPLACE(v_text,',','')).Assigning NULL to a NOT NULL NUMBER raises conversion issues inside PL/SQL. Default the variable or use NVL to supply 0.Bulk collections may hide the specific element. Loop through indices and validate each entry before assignment.

Best Practices to Avoid This Error

Adopt defensive coding: declare variables with realistic sizes, validate external data, and convert explicitly.Enable server-side logging in Galaxy’s SQL editor. The integrated runtime output makes it easy to spot the exact failing statement without sifting through long logs.Unit-test PL/SQL packages with boundary values. Automate tests inside Galaxy Collections to share verified scripts across the team.

Related Errors and Solutions

ORA-01438 occurs on INSERT or UPDATE when a value exceeds column precision. Increase column size or round the number.ORA-01722 invalid number appears in plain SQL instead of PL/SQL. Clean data or use CAST properly.ORA-06512 is a stack trace line, not an error; follow it to locate the real issue like ORA-06502.

Implicit character-to-number conversion on assignment or comparison.

Variable length smaller than incoming string, causing buffer overflow.

NUMBER precision or scale too small for the assigned value.

NULL or empty string implicitly converted to NUMBER in strict mode.

Unvalidated user input containing currency symbols, commas, or spaces.

ORA-01722: Raised during SQL when non-numeric data is compared or inserted into NUMBER columns.ORA-01438: Value larger than column precision specified for column.ORA-06512: Line reference indicating where ORA-06502 was raised.ORA-06533: Subscript beyond count, often appears in bulk operations causing ORA-06502 chain.

Does ORA-06502 always mean bad data?

No. It can also indicate variable overflow or precision mismatch even with numeric text.

Is increasing column size the only solution?

Not always. Cleaning data or using explicit conversions often resolves the error without schema changes.

Why does the error appear inside a trigger but not the main INSERT?

The INSERT may succeed, but the trigger performs additional assignments that hit invalid data.

How can Galaxy help debug ORA-06502?

Galaxys execution pane shows full PL/SQL stack traces and lets teams share corrected scripts via Collections for quick reuse.